Framebuffer子系统【转】

Framebuffer子系统【转】
本文转载自：http://blog.csdn.net/av_geek/article/details/40897115

本文将介绍Framebuffer子系统

目标平台：TQ2440 CPU：s3c2440

LCD设备：3.5英寸，分辨率320X240

1. 概述

Framebuffer，中文名字是帧缓冲，这个帧也就是一副图像所需要的数据。因此，帧缓冲其实就是LCD设备的驱动程序。Linux中，framebuffer子系统框架如下：

核心层的代码以fbmem.c为主，核心层包括许多与具体硬件无关的代码，并且提供了API给用户空间。用户空间使用系统调用，系统调用会使用相应的API函数，最后会调用驱动层实现功能。对于不同的设备，驱动层的代码将有所不同。

接下来的内容中，首先给出framerbuffer使用的数据结构；随后简单描述framerbuffer核心层；最后，针对S3C2440，对驱动代码进行分析。

2. 数据结构

 2.1 fb_info 结构

该结构是内核用于描述一个特定framebuffer设备。其中包含了几个重要的结构，将在下面介绍。

下列代码位于include/linux/fb.h
[cpp] view plain copy
1. struct fb_info {
2. int node;
3. int flags;
4. struct mutex lock; /* Lock for open/release/ioctl funcs */
5. struct fb_var_screeninfo var; /* Current var */
6. struct fb_fix_screeninfo fix; /* Current fix */
7. struct fb_monspecs monspecs; /* Current Monitor specs */
8. struct work_struct queue; /* Framebuffer event queue */
9. struct fb_pixmap pixmap; /* Image hardware mapper */
10. struct fb_pixmap sprite; /* Cursor hardware mapper */
11. struct fb_cmap cmap; /* Current cmap */
12. struct list_head modelist; /* mode list */
13. struct fb_videomode *mode; /* current mode */
15. #ifdef CONFIG_FB_BACKLIGHT
16. /* assigned backlight device */
17. /* set before framebuffer registration,
18. remove after unregister */
19. struct backlight_device *bl_dev;
21. /* Backlight level curve */
22. struct mutex bl_curve_mutex;
23. u8 bl_curve[FB_BACKLIGHT_LEVELS];
24. #endif
25. #ifdef CONFIG_FB_DEFERRED_IO
26. struct delayed_work deferred_work;
27. struct fb_deferred_io *fbdefio;
28. #endif
30. struct fb_ops *fbops;
31. struct device *device; /* This is the parent */
32. struct device *dev; /* This is this fb device */
33. int class_flag; /* private sysfs flags */
34. #ifdef CONFIG_FB_TILEBLITTING
35. struct fb_tile_ops *tileops; /* Tile Blitting */
36. #endif
37. char __iomem *screen_base; /* Virtual address */
38. unsigned long screen_size; /* Amount of ioremapped VRAM or 0 */
39. void *pseudo_palette; /* Fake palette of 16 colors */
40. #define FBINFO_STATE_RUNNING 0
41. #define FBINFO_STATE_SUSPENDED 1
42. u32 state; /* Hardware state i.e suspend */
43. void *fbcon_par; /* fbcon use-only private area */
44. /* From here on everything is device dependent */
45. void *par;
46. };
[cpp] view plain copy
1. struct fb_info {
2. int node;
3. int flags;
4. struct mutex lock; /* Lock for open/release/ioctl funcs */
5. struct fb_var_screeninfo var; /* Current var */
6. struct fb_fix_screeninfo fix; /* Current fix */
7. struct fb_monspecs monspecs; /* Current Monitor specs */
8. struct work_struct queue; /* Framebuffer event queue */
9. struct fb_pixmap pixmap; /* Image hardware mapper */
10. struct fb_pixmap sprite; /* Cursor hardware mapper */
11. struct fb_cmap cmap; /* Current cmap */
12. struct list_head modelist; /* mode list */
13. struct fb_videomode *mode; /* current mode */
15. #ifdef CONFIG_FB_BACKLIGHT
16. /* assigned backlight device */
17. /* set before framebuffer registration,
18. remove after unregister */
19. struct backlight_device *bl_dev;
21. /* Backlight level curve */
22. struct mutex bl_curve_mutex;
23. u8 bl_curve[FB_BACKLIGHT_LEVELS];
24. #endif
25. #ifdef CONFIG_FB_DEFERRED_IO
26. struct delayed_work deferred_work;
27. struct fb_deferred_io *fbdefio;
28. #endif
30. struct fb_ops *fbops;
31. struct device *device; /* This is the parent */
32. struct device *dev; /* This is this fb device */
33. int class_flag; /* private sysfs flags */
34. #ifdef CONFIG_FB_TILEBLITTING
35. struct fb_tile_ops *tileops; /* Tile Blitting */
36. #endif
37. char __iomem *screen_base; /* Virtual address */
38. unsigned long screen_size; /* Amount of ioremapped VRAM or 0 */
39. void *pseudo_palette; /* Fake palette of 16 colors */
40. #define FBINFO_STATE_RUNNING 0
41. #define FBINFO_STATE_SUSPENDED 1
42. u32 state; /* Hardware state i.e suspend */
43. void *fbcon_par; /* fbcon use-only private area */
44. /* From here on everything is device dependent */
45. void *par;
46. };
2.2 fb_fix_screeninfo结构

该数据结构是不可改变的，也就是说用户空间不能改变该结构中的任何成员，在核心层我们将会看到这点。

下列代码位于include/linux/fb.h
[cpp] view plain copy
1. struct fb_fix_screeninfo {
2. char id[16]; /* identification string eg "TT Builtin" */
3. unsigned long smem_start; /* Start of frame buffer mem */
4. /* (physical address) */
5. __u32 smem_len; /* Length of frame buffer mem */
6. __u32 type; /* see FB_TYPE_* */
7. __u32 type_aux; /* Interleave for interleaved Planes */
8. __u32 visual; /* see FB_VISUAL_* */
9. __u16 xpanstep; /* zero if no hardware panning */
10. __u16 ypanstep; /* zero if no hardware panning */
11. __u16 ywrapstep; /* zero if no hardware ywrap */
12. __u32 line_length; /* length of a line in bytes */
13. unsigned long mmio_start; /* Start of Memory Mapped I/O */
14. /* (physical address) */
15. __u32 mmio_len; /* Length of Memory Mapped I/O */
16. __u32 accel; /* Indicate to driver which */
17. /* specific chip/card we have */
18. __u16 reserved[3]; /* Reserved for future compatibility */
19. };
[cpp] view plain copy
1. struct fb_fix_screeninfo {
2. char id[16]; /* identification string eg "TT Builtin" */
3. unsigned long smem_start; /* Start of frame buffer mem */
4. /* (physical address) */
5. __u32 smem_len; /* Length of frame buffer mem */
6. __u32 type; /* see FB_TYPE_* */
7. __u32 type_aux; /* Interleave for interleaved Planes */
8. __u32 visual; /* see FB_VISUAL_* */
9. __u16 xpanstep; /* zero if no hardware panning */
10. __u16 ypanstep; /* zero if no hardware panning */
11. __u16 ywrapstep; /* zero if no hardware ywrap */
12. __u32 line_length; /* length of a line in bytes */
13. unsigned long mmio_start; /* Start of Memory Mapped I/O */
14. /* (physical address) */
15. __u32 mmio_len; /* Length of Memory Mapped I/O */
16. __u32 accel; /* Indicate to driver which */
17. /* specific chip/card we have */
18. __u16 reserved[3]; /* Reserved for future compatibility */
19. };
2.3 fb_var_screeninfo结构

该数据结构是可以改变的，也就是说用户空间可以改变该结构中的成员。该数据结构中的很多成员就由板级信息复制而来，在驱动代码中我们将会看到这点。

下列代码位于include/linux/fb.h
[cpp] view plain copy
1. struct fb_var_screeninfo {
2. __u32 xres; /* visible resolution */
3. __u32 yres;
4. __u32 xres_virtual; /* virtual resolution */
5. __u32 yres_virtual;
6. __u32 xoffset; /* offset from virtual to visible */
7. __u32 yoffset; /* resolution */
9. __u32 bits_per_pixel; /* guess what */
10. __u32 grayscale; /* != 0 Graylevels instead of colors */
12. struct fb_bitfield red; /* bitfield in fb mem if true color, */
13. struct fb_bitfield green; /* else only length is significant */
14. struct fb_bitfield blue;
15. struct fb_bitfield transp; /* transparency */
17. __u32 nonstd; /* != 0 Non standard pixel format */
19. __u32 activate; /* see FB_ACTIVATE_* */
21. __u32 height; /* height of picture in mm */
22. __u32 width; /* width of picture in mm */
24. __u32 accel_flags; /* (OBSOLETE) see fb_info.flags */
26. /* Timing: All values in pixclocks, except pixclock (of course) */
27. __u32 pixclock; /* pixel clock in ps (pico seconds) */
28. __u32 left_margin; /* time from sync to picture */
29. __u32 right_margin; /* time from picture to sync */
30. __u32 upper_margin; /* time from sync to picture */
31. __u32 lower_margin;
32. __u32 hsync_len; /* length of horizontal sync */
33. __u32 vsync_len; /* length of vertical sync */
34. __u32 sync; /* see FB_SYNC_* */
35. __u32 vmode; /* see FB_VMODE_* */
36. __u32 rotate; /* angle we rotate counter clockwise */
37. __u32 reserved[5]; /* Reserved for future compatibility */
38. };
[cpp] view plain copy
1. struct fb_var_screeninfo {
2. __u32 xres; /* visible resolution */
3. __u32 yres;
4. __u32 xres_virtual; /* virtual resolution */
5. __u32 yres_virtual;
6. __u32 xoffset; /* offset from virtual to visible */
7. __u32 yoffset; /* resolution */
9. __u32 bits_per_pixel; /* guess what */
10. __u32 grayscale; /* != 0 Graylevels instead of colors */
12. struct fb_bitfield red; /* bitfield in fb mem if true color, */
13. struct fb_bitfield green; /* else only length is significant */
14. struct fb_bitfield blue;
15. struct fb_bitfield transp; /* transparency */
17. __u32 nonstd; /* != 0 Non standard pixel format */
19. __u32 activate; /* see FB_ACTIVATE_* */
21. __u32 height; /* height of picture in mm */
22. __u32 width; /* width of picture in mm */
24. __u32 accel_flags; /* (OBSOLETE) see fb_info.flags */
26. /* Timing: All values in pixclocks, except pixclock (of course) */
27. __u32 pixclock; /* pixel clock in ps (pico seconds) */
28. __u32 left_margin; /* time from sync to picture */
29. __u32 right_margin; /* time from picture to sync */
30. __u32 upper_margin; /* time from sync to picture */
31. __u32 lower_margin;
32. __u32 hsync_len; /* length of horizontal sync */
33. __u32 vsync_len; /* length of vertical sync */
34. __u32 sync; /* see FB_SYNC_* */
35. __u32 vmode; /* see FB_VMODE_* */
36. __u32 rotate; /* angle we rotate counter clockwise */
37. __u32 reserved[5]; /* Reserved for future compatibility */
38. };
2.4 fb_ops结构

该结构描述了用于fb_info的方法，这些方法中有些是要驱动程序提供的，而有些可以使用内核提供的方法。

下列代码位于include/linux/fb.h
[cpp] view plain copy
1. /*
2. * Frame buffer operations
3. *
4. * LOCKING NOTE: those functions must _ALL_ be called with the console
5. * semaphore held, this is the only suitable locking mechanism we have
6. * in 2.6. Some may be called at interrupt time at this point though.
7. */
9. struct fb_ops {
10. /* open/release and usage marking */
11. struct module *owner;
12. int (*fb_open)(struct fb_info *info, int user);
13. int (*fb_release)(struct fb_info *info, int user);
15. /* For framebuffers with strange non linear layouts or that do not
16. * work with normal memory mapped access
17. */
18. ssize_t (*fb_read)(struct fb_info *info, char __user *buf,
19. size_t count, loff_t *ppos);
20. ssize_t (*fb_write)(struct fb_info *info, const char __user *buf,
21. size_t count, loff_t *ppos);
23. /* checks var and eventually tweaks it to something supported,
24. * DO NOT MODIFY PAR */
25. int (*fb_check_var)(struct fb_var_screeninfo *var, struct fb_info *info);
27. /* set the video mode according to info->var */
28. int (*fb_set_par)(struct fb_info *info);
30. /* set color register */
31. int (*fb_setcolreg)(unsigned regno, unsigned red, unsigned green,
32. unsigned blue, unsigned transp, struct fb_info *info);
34. /* set color registers in batch */
35. int (*fb_setcmap)(struct fb_cmap *cmap, struct fb_info *info);
37. /* blank display */
38. int (*fb_blank)(int blank, struct fb_info *info);
40. /* pan display */
41. int (*fb_pan_display)(struct fb_var_screeninfo *var, struct fb_info *info);
43. /* Draws a rectangle */
44. void (*fb_fillrect) (struct fb_info *info, const struct fb_fillrect *rect);
45. /* Copy data from area to another */
46. void (*fb_copyarea) (struct fb_info *info, const struct fb_copyarea *region);
47. /* Draws a image to the display */
48. void (*fb_imageblit) (struct fb_info *info, const struct fb_image *image);
50. /* Draws cursor */
51. int (*fb_cursor) (struct fb_info *info, struct fb_cursor *cursor);
53. /* Rotates the display */
54. void (*fb_rotate)(struct fb_info *info, int angle);
56. /* wait for blit idle, optional */
57. int (*fb_sync)(struct fb_info *info);
59. /* perform fb specific ioctl (optional) */
60. int (*fb_ioctl)(struct fb_info *info, unsigned int cmd,
61. unsigned long arg);
63. /* Handle 32bit compat ioctl (optional) */
64. int (*fb_compat_ioctl)(struct fb_info *info, unsigned cmd,
65. unsigned long arg);
67. /* perform fb specific mmap */
68. int (*fb_mmap)(struct fb_info *info, struct vm_area_struct *vma);
70. /* save current hardware state */
71. void (*fb_save_state)(struct fb_info *info);
73. /* restore saved state */
74. void (*fb_restore_state)(struct fb_info *info);
76. /* get capability given var */
77. void (*fb_get_caps)(struct fb_info *info, struct fb_blit_caps *caps,
78. struct fb_var_screeninfo *var);
79. };
[cpp] view plain copy
1. /*
2. * Frame buffer operations
3. *
4. * LOCKING NOTE: those functions must _ALL_ be called with the console
5. * semaphore held, this is the only suitable locking mechanism we have
6. * in 2.6. Some may be called at interrupt time at this point though.
7. */
9. struct fb_ops {
10. /* open/release and usage marking */
11. struct module *owner;
12. int (*fb_open)(struct fb_info *info, int user);
13. int (*fb_release)(struct fb_info *info, int user);
15. /* For framebuffers with strange non linear layouts or that do not
16. * work with normal memory mapped access
17. */
18. ssize_t (*fb_read)(struct fb_info *info, char __user *buf,
19. size_t count, loff_t *ppos);
20. ssize_t (*fb_write)(struct fb_info *info, const char __user *buf,
21. size_t count, loff_t *ppos);
23. /* checks var and eventually tweaks it to something supported,
24. * DO NOT MODIFY PAR */
25. int (*fb_check_var)(struct fb_var_screeninfo *var, struct fb_info *info);
27. /* set the video mode according to info->var */
28. int (*fb_set_par)(struct fb_info *info);
30. /* set color register */
31. int (*fb_setcolreg)(unsigned regno, unsigned red, unsigned green,
32. unsigned blue, unsigned transp, struct fb_info *info);
34. /* set color registers in batch */
35. int (*fb_setcmap)(struct fb_cmap *cmap, struct fb_info *info);
37. /* blank display */
38. int (*fb_blank)(int blank, struct fb_info *info);
40. /* pan display */
41. int (*fb_pan_display)(struct fb_var_screeninfo *var, struct fb_info *info);
43. /* Draws a rectangle */
44. void (*fb_fillrect) (struct fb_info *info, const struct fb_fillrect *rect);
45. /* Copy data from area to another */
46. void (*fb_copyarea) (struct fb_info *info, const struct fb_copyarea *region);
47. /* Draws a image to the display */
48. void (*fb_imageblit) (struct fb_info *info, const struct fb_image *image);
50. /* Draws cursor */
51. int (*fb_cursor) (struct fb_info *info, struct fb_cursor *cursor);
53. /* Rotates the display */
54. void (*fb_rotate)(struct fb_info *info, int angle);
56. /* wait for blit idle, optional */
57. int (*fb_sync)(struct fb_info *info);
59. /* perform fb specific ioctl (optional) */
60. int (*fb_ioctl)(struct fb_info *info, unsigned int cmd,
61. unsigned long arg);
63. /* Handle 32bit compat ioctl (optional) */
64. int (*fb_compat_ioctl)(struct fb_info *info, unsigned cmd,
65. unsigned long arg);
67. /* perform fb specific mmap */
68. int (*fb_mmap)(struct fb_info *info, struct vm_area_struct *vma);
70. /* save current hardware state */
71. void (*fb_save_state)(struct fb_info *info);
73. /* restore saved state */
74. void (*fb_restore_state)(struct fb_info *info);
76. /* get capability given var */
77. void (*fb_get_caps)(struct fb_info *info, struct fb_blit_caps *caps,
78. struct fb_var_screeninfo *var);
79. };
3. frambuffer核心层

首先来看下frmaebuffer子系统的初始化函数。

3.1 fbmem_init和fbmem_exit

下列代码位于drivers/video/fbmem.c
[cpp] view plain copy
1. /**
2. * fbmem_init - init frame buffer subsystem
3. *
4. * Initialize the frame buffer subsystem.
5. *
6. * NOTE: This function is _only_ to be called by drivers/char/mem.c.
7. *
8. */
10. static int __init
11. fbmem_init(void)
12. {
13. proc_create("fb", 0, NULL, &fb_proc_fops);
15. if (register_chrdev(FB_MAJOR,"fb",&fb_fops)) /*注册字符设备，major=29*/
16. printk("unable to get major %d for fb devs ", FB_MAJOR);
18. fb_class = class_create(THIS_MODULE, "graphics"); /*创建类*/
19. if (IS_ERR(fb_class)) {
20. printk(KERN_WARNING "Unable to create fb class; errno = %ld ", PTR_ERR(fb_class));
21. fb_class = NULL;
22. }
23. return 0;
24. }
26. #ifdef MODULE
27. module_init(fbmem_init);
28. static void __exit
29. fbmem_exit(void)
30. {
31. remove_proc_entry("fb", NULL);
32. class_destroy(fb_class);
33. unregister_chrdev(FB_MAJOR, "fb");
34. }
36. module_exit(fbmem_exit);
37. MODULE_LICENSE("GPL");
38. MODULE_DESCRIPTION("Framebuffer base");
39. #else
40. subsys_initcall(fbmem_init);
41. #endif
43. static const struct file_operations fb_fops = {
44. .owner = THIS_MODULE,
45. .read = fb_read,
46. .write = fb_write,
47. .unlocked_ioctl = fb_ioctl,
48. #ifdef CONFIG_COMPAT
49. .compat_ioctl = fb_compat_ioctl,
50. #endif
51. .mmap = fb_mmap,
52. .open = fb_open,
53. .release = fb_release,
54. #ifdef HAVE_ARCH_FB_UNMAPPED_AREA
55. .get_unmapped_area = get_fb_unmapped_area,
56. #endif
57. #ifdef CONFIG_FB_DEFERRED_IO
58. .fsync = fb_deferred_io_fsync,
59. #endif
60. };
[cpp] view plain copy
1. /**
2. * fbmem_init - init frame buffer subsystem
3. *
4. * Initialize the frame buffer subsystem.
5. *
6. * NOTE: This function is _only_ to be called by drivers/char/mem.c.
7. *
8. */
10. static int __init
11. fbmem_init(void)
12. {
13. proc_create("fb", 0, NULL, &fb_proc_fops);
15. if (register_chrdev(FB_MAJOR,"fb",&fb_fops)) /*注册字符设备，major=29*/
16. printk("unable to get major %d for fb devs ", FB_MAJOR);
18. fb_class = class_create(THIS_MODULE, "graphics"); /*创建类*/
19. if (IS_ERR(fb_class)) {
20. printk(KERN_WARNING "Unable to create fb class; errno = %ld ", PTR_ERR(fb_class));
21. fb_class = NULL;
22. }
23. return 0;
24. }
26. #ifdef MODULE
27. module_init(fbmem_init);
28. static void __exit
29. fbmem_exit(void)
30. {
31. remove_proc_entry("fb", NULL);
32. class_destroy(fb_class);
33. unregister_chrdev(FB_MAJOR, "fb");
34. }
36. module_exit(fbmem_exit);
37. MODULE_LICENSE("GPL");
38. MODULE_DESCRIPTION("Framebuffer base");
39. #else
40. subsys_initcall(fbmem_init);
41. #endif
43. static const struct file_operations fb_fops = {
44. .owner = THIS_MODULE,
45. .read = fb_read,
46. .write = fb_write,
47. .unlocked_ioctl = fb_ioctl,
48. #ifdef CONFIG_COMPAT
49. .compat_ioctl = fb_compat_ioctl,
50. #endif
51. .mmap = fb_mmap,
52. .open = fb_open,
53. .release = fb_release,
54. #ifdef HAVE_ARCH_FB_UNMAPPED_AREA
55. .get_unmapped_area = get_fb_unmapped_area,
56. #endif
57. #ifdef CONFIG_FB_DEFERRED_IO
58. .fsync = fb_deferred_io_fsync,
59. #endif
60. };
我们看到，如果不是作为模块，那么该初始化程序将在subsys_initcall阶段被调用。初始化时，仅仅注册了一个字符设备，并创建了一个类。通过字符设备，提供了API给用户空间，包open，release，write，read等。

随后我们看看如何分配一个fb_info结构。

3.2 framebuffer_alloc

下列代码位于drivers/video/fbmem.c
[cpp] view plain copy
1. /**
2. * framebuffer_alloc - creates a new frame buffer info structure
3. *
4. * @size: size of driver private data, can be zero
5. * @dev: pointer to the device for this fb, this can be NULL
6. *
7. * Creates a new frame buffer info structure. Also reserves @size bytes
8. * for driver private data (info->par). info->par (if any) will be
9. * aligned to sizeof(long).
10. *
11. * Returns the new structure, or NULL if an error occured.
12. *
13. */
14. struct fb_info *framebuffer_alloc(size_t size, struct device *dev)
15. {
16. #define BYTES_PER_LONG (BITS_PER_LONG/8)
17. #define PADDING (BYTES_PER_LONG - (sizeof(struct fb_info) % BYTES_PER_LONG))
18. int fb_info_size = sizeof(struct fb_info);
19. struct fb_info *info;
20. char *p;
22. if (size)
23. fb_info_size += PADDING;
25. p = kzalloc(fb_info_size + size, GFP_KERNEL);
27. if (!p)
28. return NULL;
30. info = (struct fb_info *) p;
32. if (size)
33. info->par = p + fb_info_size;
35. info->device = dev;
37. #ifdef CONFIG_FB_BACKLIGHT
38. mutex_init(&info->bl_curve_mutex);
39. #endif
41. return info;
42. #undef PADDING
43. #undef BYTES_PER_LONG
44. }
45. EXPORT_SYMBOL(framebuffer_alloc);
[cpp] view plain copy
1. /**
2. * framebuffer_alloc - creates a new frame buffer info structure
3. *
4. * @size: size of driver private data, can be zero
5. * @dev: pointer to the device for this fb, this can be NULL
6. *
7. * Creates a new frame buffer info structure. Also reserves @size bytes
8. * for driver private data (info->par). info->par (if any) will be
9. * aligned to sizeof(long).
10. *
11. * Returns the new structure, or NULL if an error occured.
12. *
13. */
14. struct fb_info *framebuffer_alloc(size_t size, struct device *dev)
15. {
16. #define BYTES_PER_LONG (BITS_PER_LONG/8)
17. #define PADDING (BYTES_PER_LONG - (sizeof(struct fb_info) % BYTES_PER_LONG))
18. int fb_info_size = sizeof(struct fb_info);
19. struct fb_info *info;
20. char *p;
22. if (size)
23. fb_info_size += PADDING;
25. p = kzalloc(fb_info_size + size, GFP_KERNEL);
27. if (!p)
28. return NULL;
30. info = (struct fb_info *) p;
32. if (size)
33. info->par = p + fb_info_size;
35. info->device = dev;
37. #ifdef CONFIG_FB_BACKLIGHT
38. mutex_init(&info->bl_curve_mutex);
39. #endif
41. return info;
42. #undef PADDING
43. #undef BYTES_PER_LONG
44. }
45. EXPORT_SYMBOL(framebuffer_alloc);
在进行分配时，根据参数size的大小，分配了b_info_size + size的空间，然后让fb_info->par指向size的空间。因此par所指向的空间可视为设备特有的数据。

在分配了fb_info结构之后，需要将它注册到内核中。注册由register_framebuffer完成。我们来看下。

3.3 register_framebuffer

下列代码位于drivers/video/fbmem.c
[cpp] view plain copy
1. /**
2. * register_framebuffer - registers a frame buffer device
3. * @fb_info: frame buffer info structure
4. *
5. * Registers a frame buffer device @fb_info.
6. *
7. * Returns negative errno on error, or zero for success.
8. *
9. */
11. int
12. register_framebuffer(struct fb_info *fb_info)
13. {
14. int i;
15. struct fb_event event;
16. struct fb_videomode mode;
18. if (num_registered_fb == FB_MAX) /*最多32个FB*/
19. return -ENXIO;
21. if (fb_check_foreignness(fb_info))
22. return -ENOSYS;
24. num_registered_fb++; /*对注册的FB计数*/
25. /*寻找第一个空位*/
26. for (i = 0 ; i < FB_MAX; i++)/*FB_MAX=32,也就是最多32个framebuffer*/
27. if (!registered_fb[i]) /*struct fb_info *registered_fb[FB_MAX]*/
28. break;
29. fb_info->node = i;
30. mutex_init(&fb_info->lock); /*初始化互斥体*/
32. fb_info->dev = device_create(fb_class, fb_info->device,/*创建设备节点，节点名为fbx*/
33. MKDEV(FB_MAJOR, i), NULL, "fb%d", i);
34. if (IS_ERR(fb_info->dev)) {
35. /* Not fatal */
36. printk(KERN_WARNING "Unable to create device for framebuffer %d; errno = %ld ", i, PTR_ERR(fb_info->dev));
37. fb_info->dev = NULL;
38. } else
39. fb_init_device(fb_info); /*初始化,在class/graphics/fbx/下创建设备属性*/
41. if (fb_info->pixmap.addr == NULL) {
42. fb_info->pixmap.addr = kmalloc(FBPIXMAPSIZE, GFP_KERNEL);/*分配内存，1024 * 8字节*/
43. if (fb_info->pixmap.addr) {
44. fb_info->pixmap.size = FBPIXMAPSIZE;
45. fb_info->pixmap.buf_align = 1;
46. fb_info->pixmap.scan_align = 1;
47. fb_info->pixmap.access_align = 32;
48. fb_info->pixmap.flags = FB_PIXMAP_DEFAULT;
49. }
50. }
51. fb_info->pixmap.offset = 0;
53. if (!fb_info->pixmap.blit_x)
54. fb_info->pixmap.blit_x = ~(u32)0;
56. if (!fb_info->pixmap.blit_y)
57. fb_info->pixmap.blit_y = ~(u32)0;
59. if (!fb_info->modelist.prev || !fb_info->modelist.next) /*该链表没有指向其他节点*/
60. INIT_LIST_HEAD(&fb_info->modelist); /*初始化链表头*/
62. fb_var_to_videomode(&mode, &fb_info->var);/*转换fb_var_screeninfo成fb_videomode*/
63. fb_add_videomode(&mode, &fb_info->modelist);/*添加mode至链表中*/
64. registered_fb[i] = fb_info;
66. event.info = fb_info;
67. if (!lock_fb_info(fb_info))
68. return -ENODEV;
69. fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event);/*???*/
70. unlock_fb_info(fb_info);
71. return 0;
72. }
[cpp] view plain copy
1. /**
2. * register_framebuffer - registers a frame buffer device
3. * @fb_info: frame buffer info structure
4. *
5. * Registers a frame buffer device @fb_info.
6. *
7. * Returns negative errno on error, or zero for success.
8. *
9. */
11. int
12. register_framebuffer(struct fb_info *fb_info)
13. {
14. int i;
15. struct fb_event event;
16. struct fb_videomode mode;
18. if (num_registered_fb == FB_MAX) /*最多32个FB*/
19. return -ENXIO;
21. if (fb_check_foreignness(fb_info))
22. return -ENOSYS;
24. num_registered_fb++; /*对注册的FB计数*/
25. /*寻找第一个空位*/
26. for (i = 0 ; i < FB_MAX; i++)/*FB_MAX=32,也就是最多32个framebuffer*/
27. if (!registered_fb[i]) /*struct fb_info *registered_fb[FB_MAX]*/
28. break;
29. fb_info->node = i;
30. mutex_init(&fb_info->lock); /*初始化互斥体*/
32. fb_info->dev = device_create(fb_class, fb_info->device,/*创建设备节点，节点名为fbx*/
33. MKDEV(FB_MAJOR, i), NULL, "fb%d", i);
34. if (IS_ERR(fb_info->dev)) {
35. /* Not fatal */
36. printk(KERN_WARNING "Unable to create device for framebuffer %d; errno = %ld ", i, PTR_ERR(fb_info->dev));
37. fb_info->dev = NULL;
38. } else
39. fb_init_device(fb_info); /*初始化,在class/graphics/fbx/下创建设备属性*/
41. if (fb_info->pixmap.addr == NULL) {
42. fb_info->pixmap.addr = kmalloc(FBPIXMAPSIZE, GFP_KERNEL);/*分配内存，1024 * 8字节*/
43. if (fb_info->pixmap.addr) {
44. fb_info->pixmap.size = FBPIXMAPSIZE;
45. fb_info->pixmap.buf_align = 1;
46. fb_info->pixmap.scan_align = 1;
47. fb_info->pixmap.access_align = 32;
48. fb_info->pixmap.flags = FB_PIXMAP_DEFAULT;
49. }
50. }
51. fb_info->pixmap.offset = 0;
53. if (!fb_info->pixmap.blit_x)
54. fb_info->pixmap.blit_x = ~(u32)0;
56. if (!fb_info->pixmap.blit_y)
57. fb_info->pixmap.blit_y = ~(u32)0;
59. if (!fb_info->modelist.prev || !fb_info->modelist.next) /*该链表没有指向其他节点*/
60. INIT_LIST_HEAD(&fb_info->modelist); /*初始化链表头*/
62. fb_var_to_videomode(&mode, &fb_info->var);/*转换fb_var_screeninfo成fb_videomode*/
63. fb_add_videomode(&mode, &fb_info->modelist);/*添加mode至链表中*/
64. registered_fb[i] = fb_info;
66. event.info = fb_info;
67. if (!lock_fb_info(fb_info))
68. return -ENODEV;
69. fb_notifier_call_chain(FB_EVENT_FB_REGISTERED, &event);/*???*/
70. unlock_fb_info(fb_info);
71. return 0;
72. }
从这个函数我们可以看出，framebuffer子系统只支持32个设备。在创建了设备节点以后，建立设备属性节点，随后将fb_var_screeninfo转换成fb_videomode，最后添加fb_videomode至链表中。

我们看下其中调用的函数，首先是fb_init_device。

下列代码位于drivers/video/fbsysfs.c
[cpp] view plain copy
1. int fb_init_device(struct fb_info *fb_info)
2. {
3. int i, error = 0;
5. dev_set_drvdata(fb_info->dev, fb_info);
7. fb_info->class_flag |= FB_SYSFS_FLAG_ATTR;
9. /*建立设备属性*/
10. for (i = 0; i < ARRAY_SIZE(device_attrs); i++) {
11. error = device_create_file(fb_info->dev, &device_attrs[i]);
13. if (error)
14. break;
15. }
17. if (error) {
18. while (--i >= 0)
19. device_remove_file(fb_info->dev, &device_attrs[i]);
20. fb_info->class_flag &= ~FB_SYSFS_FLAG_ATTR;
21. }
23. return 0;
24. }
26. /* When cmap is added back in it should be a binary attribute
27. * not a text one. Consideration should also be given to converting
28. * fbdev to use configfs instead of sysfs */
29. static struct device_attribute device_attrs[] = {
30. __ATTR(bits_per_pixel, S_IRUGO|S_IWUSR, show_bpp, store_bpp),
31. __ATTR(blank, S_IRUGO|S_IWUSR, show_blank, store_blank),
32. __ATTR(console, S_IRUGO|S_IWUSR, show_console, store_console),
33. __ATTR(cursor, S_IRUGO|S_IWUSR, show_cursor, store_cursor),
34. __ATTR(mode, S_IRUGO|S_IWUSR, show_mode, store_mode),
35. __ATTR(modes, S_IRUGO|S_IWUSR, show_modes, store_modes),
36. __ATTR(pan, S_IRUGO|S_IWUSR, show_pan, store_pan),
37. __ATTR(virtual_size, S_IRUGO|S_IWUSR, show_virtual, store_virtual),
38. __ATTR(name, S_IRUGO, show_name, NULL),
39. __ATTR(stride, S_IRUGO, show_stride, NULL),
40. __ATTR(rotate, S_IRUGO|S_IWUSR, show_rotate, store_rotate),
41. __ATTR(state, S_IRUGO|S_IWUSR, show_fbstate, store_fbstate),
42. #ifdef CONFIG_FB_BACKLIGHT
43. __ATTR(bl_curve, S_IRUGO|S_IWUSR, show_bl_curve, store_bl_curve),
44. #endif
45. };
[cpp] view plain copy
1. int fb_init_device(struct fb_info *fb_info)
2. {
3. int i, error = 0;
5. dev_set_drvdata(fb_info->dev, fb_info);
7. fb_info->class_flag |= FB_SYSFS_FLAG_ATTR;
9. /*建立设备属性*/
10. for (i = 0; i < ARRAY_SIZE(device_attrs); i++) {
11. error = device_create_file(fb_info->dev, &device_attrs[i]);
13. if (error)
14. break;
15. }
17. if (error) {
18. while (--i >= 0)
19. device_remove_file(fb_info->dev, &device_attrs[i]);
20. fb_info->class_flag &= ~FB_SYSFS_FLAG_ATTR;
21. }
23. return 0;
24. }
26. /* When cmap is added back in it should be a binary attribute
27. * not a text one. Consideration should also be given to converting
28. * fbdev to use configfs instead of sysfs */
29. static struct device_attribute device_attrs[] = {
30. __ATTR(bits_per_pixel, S_IRUGO|S_IWUSR, show_bpp, store_bpp),
31. __ATTR(blank, S_IRUGO|S_IWUSR, show_blank, store_blank),
32. __ATTR(console, S_IRUGO|S_IWUSR, show_console, store_console),
33. __ATTR(cursor, S_IRUGO|S_IWUSR, show_cursor, store_cursor),
34. __ATTR(mode, S_IRUGO|S_IWUSR, show_mode, store_mode),
35. __ATTR(modes, S_IRUGO|S_IWUSR, show_modes, store_modes),
36. __ATTR(pan, S_IRUGO|S_IWUSR, show_pan, store_pan),
37. __ATTR(virtual_size, S_IRUGO|S_IWUSR, show_virtual, store_virtual),
38. __ATTR(name, S_IRUGO, show_name, NULL),
39. __ATTR(stride, S_IRUGO, show_stride, NULL),
40. __ATTR(rotate, S_IRUGO|S_IWUSR, show_rotate, store_rotate),
41. __ATTR(state, S_IRUGO|S_IWUSR, show_fbstate, store_fbstate),
42. #ifdef CONFIG_FB_BACKLIGHT
43. __ATTR(bl_curve, S_IRUGO|S_IWUSR, show_bl_curve, store_bl_curve),
44. #endif
45. };
我们可以在/sys/class/graphics/fb0下发现这些属性文件。

[root@yj423 fb0]#pwd
/sys/class/graphics/fb0
[root@yj423 fb0]#ls
bits_per_pixel cursor          mode            pan             state           uevent
blank           dev             modes           power           stride          virtual_size
console         device          name            rotate          subsystem

接着看下fb_var_to_videomode和fb_add_videomode函数。

下列代码位于drivers/video/modedb.c和drivers/video/fb.h
[cpp] view plain copy
1. struct fb_videomode {
2. const char *name; /* optional */
3. u32 refresh; /* optional */
4. u32 xres;
5. u32 yres;
6. u32 pixclock;
7. u32 left_margin;
8. u32 right_margin;
9. u32 upper_margin;
10. u32 lower_margin;
11. u32 hsync_len;
12. u32 vsync_len;
13. u32 sync;
14. u32 vmode;
15. u32 flag;
16. };
18. /**
19. * fb_var_to_videomode - convert fb_var_screeninfo to fb_videomode
20. * @mode: pointer to struct fb_videomode
21. * @var: pointer to struct fb_var_screeninfo
22. */
23. void fb_var_to_videomode(struct fb_videomode *mode,
24. const struct fb_var_screeninfo *var)
25. {
26. u32 pixclock, hfreq, htotal, vtotal;
28. mode->name = NULL;
29. mode->xres = var->xres;
30. mode->yres = var->yres;
31. mode->pixclock = var->pixclock;
32. mode->hsync_len = var->hsync_len;
33. mode->vsync_len = var->vsync_len;
34. mode->left_margin = var->left_margin;
35. mode->right_margin = var->right_margin;
36. mode->upper_margin = var->upper_margin;
37. mode->lower_margin = var->lower_margin;
38. mode->sync = var->sync;
39. mode->vmode = var->vmode & FB_VMODE_MASK;
40. mode->flag = FB_MODE_IS_FROM_VAR;
41. mode->refresh = 0;
43. if (!var->pixclock)
44. return;
46. pixclock = PICOS2KHZ(var->pixclock) * 1000;
48. htotal = var->xres + var->right_margin + var->hsync_len +
49. var->left_margin;
50. vtotal = var->yres + var->lower_margin + var->vsync_len +
51. var->upper_margin;
53. if (var->vmode & FB_VMODE_INTERLACED)
54. vtotal /= 2;
55. if (var->vmode & FB_VMODE_DOUBLE)
56. vtotal *= 2;
58. hfreq = pixclock/htotal;
59. mode->refresh = hfreq/vtotal;
60. }
62. /**
63. * fb_add_videomode: adds videomode entry to modelist
64. * @mode: videomode to add
65. * @head: struct list_head of modelist
66. *
67. * NOTES:
68. * Will only add unmatched mode entries
69. */
70. int fb_add_videomode(const struct fb_videomode *mode, struct list_head *head)
71. {
72. struct list_head *pos;
73. struct fb_modelist *modelist;d
74. struct fb_videomode *m;
75. int found = 0;
76. /*遍历所有的fb_modelist，查找mode是否存在*/
77. list_for_each(pos, head) {
78. modelist = list_entry(pos, struct fb_modelist, list);
79. m = &modelist->mode;
80. if (fb_mode_is_equal(m, mode)) { /*比较两个fb_videomode*/
81. found = 1; /*该fb_videomode已存在*/
82. break;
83. }
84. }
85. if (!found) { /*不存在*/
86. modelist = kmalloc(sizeof(struct fb_modelist), /*分配fb_modelist*/
87. GFP_KERNEL);
89. if (!modelist)
90. return -ENOMEM;
91. modelist->mode = *mode; /*保存mode*/
92. list_add(&modelist->list, head);/*添加mode至链表中*/
93. }
94. return 0;
95. }
97. /**
98. * fb_mode_is_equal - compare 2 videomodes
99. * @mode1: first videomode
100. * @mode2: second videomode
101. *
102. * RETURNS:
103. * 1 if equal, 0 if not
104. */
105. int fb_mode_is_equal(const struct fb_videomode *mode1,
106. const struct fb_videomode *mode2)
107. {
108. return (mode1->xres == mode2->xres &&
109. mode1->yres == mode2->yres &&
110. mode1->pixclock == mode2->pixclock &&
111. mode1->hsync_len == mode2->hsync_len &&
112. mode1->vsync_len == mode2->vsync_len &&
113. mode1->left_margin == mode2->left_margin &&
114. mode1->right_margin == mode2->right_margin &&
115. mode1->upper_margin == mode2->upper_margin &&
116. mode1->lower_margin == mode2->lower_margin &&
117. mode1->sync == mode2->sync &&
118. mode1->vmode == mode2->vmode);
119. }
[cpp] view plain copy
1. struct fb_videomode {
2. const char *name; /* optional */
3. u32 refresh; /* optional */
4. u32 xres;
5. u32 yres;
6. u32 pixclock;
7. u32 left_margin;
8. u32 right_margin;
9. u32 upper_margin;
10. u32 lower_margin;
11. u32 hsync_len;
12. u32 vsync_len;
13. u32 sync;
14. u32 vmode;
15. u32 flag;
16. };
18. /**
19. * fb_var_to_videomode - convert fb_var_screeninfo to fb_videomode
20. * @mode: pointer to struct fb_videomode
21. * @var: pointer to struct fb_var_screeninfo
22. */
23. void fb_var_to_videomode(struct fb_videomode *mode,
24. const struct fb_var_screeninfo *var)
25. {
26. u32 pixclock, hfreq, htotal, vtotal;
28. mode->name = NULL;
29. mode->xres = var->xres;
30. mode->yres = var->yres;
31. mode->pixclock = var->pixclock;
32. mode->hsync_len = var->hsync_len;
33. mode->vsync_len = var->vsync_len;
34. mode->left_margin = var->left_margin;
35. mode->right_margin = var->right_margin;
36. mode->upper_margin = var->upper_margin;
37. mode->lower_margin = var->lower_margin;
38. mode->sync = var->sync;
39. mode->vmode = var->vmode & FB_VMODE_MASK;
40. mode->flag = FB_MODE_IS_FROM_VAR;
41. mode->refresh = 0;
43. if (!var->pixclock)
44. return;
46. pixclock = PICOS2KHZ(var->pixclock) * 1000;
48. htotal = var->xres + var->right_margin + var->hsync_len +
49. var->left_margin;
50. vtotal = var->yres + var->lower_margin + var->vsync_len +
51. var->upper_margin;
53. if (var->vmode & FB_VMODE_INTERLACED)
54. vtotal /= 2;
55. if (var->vmode & FB_VMODE_DOUBLE)
56. vtotal *= 2;
58. hfreq = pixclock/htotal;
59. mode->refresh = hfreq/vtotal;
60. }
62. /**
63. * fb_add_videomode: adds videomode entry to modelist
64. * @mode: videomode to add
65. * @head: struct list_head of modelist
66. *
67. * NOTES:
68. * Will only add unmatched mode entries
69. */
70. int fb_add_videomode(const struct fb_videomode *mode, struct list_head *head)
71. {
72. struct list_head *pos;
73. struct fb_modelist *modelist;d
74. struct fb_videomode *m;
75. int found = 0;
76. /*遍历所有的fb_modelist，查找mode是否存在*/
77. list_for_each(pos, head) {
78. modelist = list_entry(pos, struct fb_modelist, list);
79. m = &modelist->mode;
80. if (fb_mode_is_equal(m, mode)) { /*比较两个fb_videomode*/
81. found = 1; /*该fb_videomode已存在*/
82. break;
83. }
84. }
85. if (!found) { /*不存在*/
86. modelist = kmalloc(sizeof(struct fb_modelist), /*分配fb_modelist*/
87. GFP_KERNEL);
89. if (!modelist)
90. return -ENOMEM;
91. modelist->mode = *mode; /*保存mode*/
92. list_add(&modelist->list, head);/*添加mode至链表中*/
93. }
94. return 0;
95. }
97. /**
98. * fb_mode_is_equal - compare 2 videomodes
99. * @mode1: first videomode
100. * @mode2: second videomode
101. *
102. * RETURNS:
103. * 1 if equal, 0 if not
104. */
105. int fb_mode_is_equal(const struct fb_videomode *mode1,
106. const struct fb_videomode *mode2)
107. {
108. return (mode1->xres == mode2->xres &&
109. mode1->yres == mode2->yres &&
110. mode1->pixclock == mode2->pixclock &&
111. mode1->hsync_len == mode2->hsync_len &&
112. mode1->vsync_len == mode2->vsync_len &&
113. mode1->left_margin == mode2->left_margin &&
114. mode1->right_margin == mode2->right_margin &&
115. mode1->upper_margin == mode2->upper_margin &&
116. mode1->lower_margin == mode2->lower_margin &&
117. mode1->sync == mode2->sync &&
118. mode1->vmode == mode2->vmode);
119. }
fb_var_to_videomode函数只是将fb_var_screeninfo结构转换成fb_videomode结构。而fb_add_videomode函数查找是否该fb_videomode已经存在，如果不存在则添加到列表中。

3.4 字符设备方法

在看过framebuffer子系统建立和注册过程后，我们看下framebuffer留给用户空间的API是怎样实现的。

本小结只分析5个常用的方法，即open，release，read，write和ioctl。

因为所有的方法和struct fb_ops定义的方法有紧密的联系，而该结构的定义由驱动程序给出，在这里我们提前看下在驱动中是如何定义的。

下列代码位于drivers/video/s3c2410fb..c
[cpp] view plain copy
1. static struct fb_ops s3c2410fb_ops = {
2. .owner = THIS_MODULE,
3. .fb_check_var = s3c2410fb_check_var, /*检查变量的合法性*/
4. .fb_set_par = s3c2410fb_set_par, /*将参数写入LCD控制器，该函数由帧缓冲核心调用*/
5. .fb_blank = s3c2410fb_blank, /*该方法支持显示消隐和去消隐*/
6. .fb_setcolreg = s3c2410fb_setcolreg, /*设置颜色寄存器*/
7. .fb_fillrect = cfb_fillrect, /*用像素行填充矩形框，通用库函数*/
8. .fb_copyarea = cfb_copyarea, /*将屏幕的一个矩形区域复制到另一个区域，通用库函数*/
9. .fb_imageblit = cfb_imageblit, /*显示一副图像，通用库函数*/
10. };
[cpp] view plain copy
1. static struct fb_ops s3c2410fb_ops = {
2. .owner = THIS_MODULE,
3. .fb_check_var = s3c2410fb_check_var, /*检查变量的合法性*/
4. .fb_set_par = s3c2410fb_set_par, /*将参数写入LCD控制器，该函数由帧缓冲核心调用*/
5. .fb_blank = s3c2410fb_blank, /*该方法支持显示消隐和去消隐*/
6. .fb_setcolreg = s3c2410fb_setcolreg, /*设置颜色寄存器*/
7. .fb_fillrect = cfb_fillrect, /*用像素行填充矩形框，通用库函数*/
8. .fb_copyarea = cfb_copyarea, /*将屏幕的一个矩形区域复制到另一个区域，通用库函数*/
9. .fb_imageblit = cfb_imageblit, /*显示一副图像，通用库函数*/
10. };
最下面的三个方法使用的是内核提供的库函数，而上面4个则是由驱动提供。

3.4.1 open方法

下列代码位于drivers/video/fbmem.c
[cpp] view plain copy
1. static int
2. fb_open(struct inode *inode, struct file *file)
3. __acquires(&info->lock)
4. __releases(&info->lock)
5. {
6. int fbidx = iminor(inode);
7. struct fb_info *info;
8. int res = 0;
10. if (fbidx >= FB_MAX)
11. return -ENODEV;
12. info = registered_fb[fbidx]; /*在register_framebuffer函数中已经设置了元素*/
13. if (!info)
14. request_module("fb%d", fbidx); /*加载模块，这里不加载*/
15. info = registered_fb[fbidx];
16. if (!info)
17. return -ENODEV;
18. mutex_lock(&info->lock); /*加锁互斥体*/
19. if (!try_module_get(info->fbops->owner)) { /*增加模块引用计数*/
20. res = -ENODEV;
21. goto out;
22. }
23. file->private_data = info; /*保存info*/
24. if (info->fbops->fb_open) { /*这里fb_open方法为空*/
25. res = info->fbops->fb_open(info,1);
26. if (res)
27. module_put(info->fbops->owner);
28. }
29. #ifdef CONFIG_FB_DEFERRED_IO
30. if (info->fbdefio)
31. fb_deferred_io_open(info, inode, file);
32. #endif
33. out:
34. mutex_unlock(&info->lock); /*解锁互斥体*/
35. return res;
36. }
[cpp] view plain copy
1. static int
2. fb_open(struct inode *inode, struct file *file)
3. __acquires(&info->lock)
4. __releases(&info->lock)
5. {
6. int fbidx = iminor(inode);
7. struct fb_info *info;
8. int res = 0;
10. if (fbidx >= FB_MAX)
11. return -ENODEV;
12. info = registered_fb[fbidx]; /*在register_framebuffer函数中已经设置了元素*/
13. if (!info)
14. request_module("fb%d", fbidx); /*加载模块，这里不加载*/
15. info = registered_fb[fbidx];
16. if (!info)
17. return -ENODEV;
18. mutex_lock(&info->lock); /*加锁互斥体*/
19. if (!try_module_get(info->fbops->owner)) { /*增加模块引用计数*/
20. res = -ENODEV;
21. goto out;
22. }
23. file->private_data = info; /*保存info*/
24. if (info->fbops->fb_open) { /*这里fb_open方法为空*/
25. res = info->fbops->fb_open(info,1);
26. if (res)
27. module_put(info->fbops->owner);
28. }
29. #ifdef CONFIG_FB_DEFERRED_IO
30. if (info->fbdefio)
31. fb_deferred_io_open(info, inode, file);
32. #endif
33. out:
34. mutex_unlock(&info->lock); /*解锁互斥体*/
35. return res;
36. }
主要的一个工作就是增加模块引用计数。还有，程序会判断是否fb_open在驱动中给出，如果有则调用该方法。我们已经知道fb_open没有给出。

3.4.2 release方法

下列代码位于drivers/video/fbmem.c
[cpp] view plain copy
1. static int
2. fb_release(struct inode *inode, struct file *file)
3. __acquires(&info->lock)
4. __releases(&info->lock)
5. {
6. struct fb_info * const info = file->private_data;
8. mutex_lock(&info->lock);
9. if (info->fbops->fb_release) /*这里fb_release为空*/
10. info->fbops->fb_release(info,1);
11. module_put(info->fbops->owner); /*减少模块引用计数*/
12. mutex_unlock(&info->lock);
13. return 0;
14. }
[cpp] view plain copy
1. static int
2. fb_release(struct inode *inode, struct file *file)
3. __acquires(&info->lock)
4. __releases(&info->lock)
5. {
6. struct fb_info * const info = file->private_data;
8. mutex_lock(&info->lock);
9. if (info->fbops->fb_release) /*这里fb_release为空*/
10. info->fbops->fb_release(info,1);
11. module_put(info->fbops->owner); /*减少模块引用计数*/
12. mutex_unlock(&info->lock);
13. return 0;
14. }
和open相反，减少模块引用计数。

3.4.3 write方法

通过调用该方法，LCD将显示画面。

下列代码位于drivers/video/fbmem.c
[cpp] view plain copy
1. static ssize_t
2. fb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
3. {
4. unsigned long p = *ppos;
5. struct inode *inode = file->f_path.dentry->d_inode;
6. int fbidx = iminor(inode);
7. struct fb_info *info = registered_fb[fbidx];
8. u32 *buffer, *src;
9. u32 __iomem *dst;
10. int c, i, cnt = 0, err = 0;
11. unsigned long total_size;
13. if (!info || !info->screen_base) /*screen_base在驱动中给出*/
14. return -ENODEV;
16. if (info->state != FBINFO_STATE_RUNNING)
17. return -EPERM;
19. if (info->fbops->fb_write) /*没有fb_write方法*/
20. return info->fbops->fb_write(info, buf, count, ppos);
22. total_size = info->screen_size; /*screen_size没有给出*/
24. if (total_size == 0)
25. total_size = info->fix.smem_len;/*153600字节，驱动probe方法中计算*/
27. if (p > total_size)
28. return -EFBIG;
30. if (count > total_size) { /*要写入的字节数大于153600*/
31. err = -EFBIG; /*file too big*/
32. count = total_size;
33. }
35. if (count + p > total_size) {/*偏移量加上字节数超出了缓冲区*/
36. if (!err)
37. err = -ENOSPC;
39. count = total_size - p;
40. }
42. /*分配buffer，GFP_KERNEL*/
43. buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
44. GFP_KERNEL); /
45. if (!buffer)
46. return -ENOMEM;
48. dst = (u32 __iomem *) (info->screen_base + p);/*修改目的指针*/
50. if (info->fbops->fb_sync) /*没有定义fb_sync*/
51. info->fbops->fb_sync(info);
53. while (count) {
54. c = (count > PAGE_SIZE) ? PAGE_SIZE : count;
55. src = buffer;
57. /*从buf(用户空间)拷贝数据到src中，一开始为1页，最后为count字节*/
58. if (copy_from_user(src, buf, c)) {
59. err = -EFAULT;
60. break;
61. }
62. /*一次for循环，写入4个字节数据到dst处*/
63. for (i = c >> 2; i--; )
64. fb_writel(*src++, dst++);
65. /*最后还有3个，2个或者1个字节*/
66. if (c & 3) {
67. u8 *src8 = (u8 *) src;
68. u8 __iomem *dst8 = (u8 __iomem *) dst;
69. /*一次写入一个字节*/
70. for (i = c & 3; i--; )
71. fb_writeb(*src8++, dst8++);
73. dst = (u32 __iomem *) dst8;
74. }
76. *ppos += c; /*用户空间偏移量增加*/
77. buf += c; /*用户空间指针增加*/
78. cnt += c; /*修改已发送字节数*/
79. count -= c; /*减去1页*/
80. }
82. kfree(buffer); /*释放buffer*/
84. return (cnt) ? cnt : err;
85. }
[cpp] view plain copy
1. static ssize_t
2. fb_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
3. {
4. unsigned long p = *ppos;
5. struct inode *inode = file->f_path.dentry->d_inode;
6. int fbidx = iminor(inode);
7. struct fb_info *info = registered_fb[fbidx];
8. u32 *buffer, *src;
9. u32 __iomem *dst;
10. int c, i, cnt = 0, err = 0;
11. unsigned long total_size;
13. if (!info || !info->screen_base) /*screen_base在驱动中给出*/
14. return -ENODEV;
16. if (info->state != FBINFO_STATE_RUNNING)
17. return -EPERM;
19. if (info->fbops->fb_write) /*没有fb_write方法*/
20. return info->fbops->fb_write(info, buf, count, ppos);
22. total_size = info->screen_size; /*screen_size没有给出*/
24. if (total_size == 0)
25. total_size = info->fix.smem_len;/*153600字节，驱动probe方法中计算*/
27. if (p > total_size)
28. return -EFBIG;
30. if (count > total_size) { /*要写入的字节数大于153600*/
31. err = -EFBIG; /*file too big*/
32. count = total_size;
33. }
35. if (count + p > total_size) {/*偏移量加上字节数超出了缓冲区*/
36. if (!err)
37. err = -ENOSPC;
39. count = total_size - p;
40. }
42. /*分配buffer，GFP_KERNEL*/
43. buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
44. GFP_KERNEL); /
45. if (!buffer)
46. return -ENOMEM;
48. dst = (u32 __iomem *) (info->screen_base + p);/*修改目的指针*/
50. if (info->fbops->fb_sync) /*没有定义fb_sync*/
51. info->fbops->fb_sync(info);
53. while (count) {
54. c = (count > PAGE_SIZE) ? PAGE_SIZE : count;
55. src = buffer;
57. /*从buf(用户空间)拷贝数据到src中，一开始为1页，最后为count字节*/
58. if (copy_from_user(src, buf, c)) {
59. err = -EFAULT;
60. break;
61. }
62. /*一次for循环，写入4个字节数据到dst处*/
63. for (i = c >> 2; i--; )
64. fb_writel(*src++, dst++);
65. /*最后还有3个，2个或者1个字节*/
66. if (c & 3) {
67. u8 *src8 = (u8 *) src;
68. u8 __iomem *dst8 = (u8 __iomem *) dst;
69. /*一次写入一个字节*/
70. for (i = c & 3; i--; )
71. fb_writeb(*src8++, dst8++);
73. dst = (u32 __iomem *) dst8;
74. }
76. *ppos += c; /*用户空间偏移量增加*/
77. buf += c; /*用户空间指针增加*/
78. cnt += c; /*修改已发送字节数*/
79. count -= c; /*减去1页*/
80. }
82. kfree(buffer); /*释放buffer*/
84. return (cnt) ? cnt : err;
85. }
这里，做了一系列的检查之后，开始拷贝数据。这里一个有三个buffer，一个是用户空间提供的buf，一个是在这里新开辟的buffer，还有就是驱动层提供的screen_base。

数据流如下：

用户空间的数据首先被复制到buffer中，然后从buffer中复制到screen_base中，最后被映射到LCD上，LCD就显示响应的画面了。

3.4.4 read方法

该方法用于读取屏幕画面的数据。

read和write类似，只是数据流是反响的，就不多做介绍了。

下列代码位于drivers/video/fbmem.c
[cpp] view plain copy
1. static ssize_t
2. fb_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
3. {
4. unsigned long p = *ppos;
5. struct inode *inode = file->f_path.dentry->d_inode;
6. int fbidx = iminor(inode);
7. struct fb_info *info = registered_fb[fbidx];
8. u32 *buffer, *dst;
9. u32 __iomem *src;
10. int c, i, cnt = 0, err = 0;
11. unsigned long total_size;
13. if (!info || ! info->screen_base)
14. return -ENODEV;
16. if (info->state != FBINFO_STATE_RUNNING)
17. return -EPERM;
19. if (info->fbops->fb_read) /*没有定义fb_read*/
20. return info->fbops->fb_read(info, buf, count, ppos);
22. total_size = info->screen_size;
24. if (total_size == 0)
25. total_size = info->fix.smem_len;
27. if (p >= total_size)
28. return 0;
30. if (count >= total_size)
31. count = total_size;
33. if (count + p > total_size)
34. count = total_size - p;
36. buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
37. GFP_KERNEL);
38. if (!buffer)
39. return -ENOMEM;
41. src = (u32 __iomem *) (info->screen_base + p);
43. if (info->fbops->fb_sync)
44. info->fbops->fb_sync(info);/*没有定义fb_sync*/
46. while (count) {
47. c = (count > PAGE_SIZE) ? PAGE_SIZE : count;
48. dst = buffer;
49. for (i = c >> 2; i--; )
50. *dst++ = fb_readl(src++);
51. if (c & 3) {
52. u8 *dst8 = (u8 *) dst;
53. u8 __iomem *src8 = (u8 __iomem *) src;
55. for (i = c & 3; i--;)
56. *dst8++ = fb_readb(src8++);
58. src = (u32 __iomem *) src8;
59. }
61. if (copy_to_user(buf, buffer, c)) {
62. err = -EFAULT;
63. break;
64. }
65. *ppos += c;
66. buf += c;
67. cnt += c;
68. count -= c;
69. }
71. kfree(buffer);
73. return (err) ? err : cnt;
74. }
[cpp] view plain copy
1. static ssize_t
2. fb_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
3. {
4. unsigned long p = *ppos;
5. struct inode *inode = file->f_path.dentry->d_inode;
6. int fbidx = iminor(inode);
7. struct fb_info *info = registered_fb[fbidx];
8. u32 *buffer, *dst;
9. u32 __iomem *src;
10. int c, i, cnt = 0, err = 0;
11. unsigned long total_size;
13. if (!info || ! info->screen_base)
14. return -ENODEV;
16. if (info->state != FBINFO_STATE_RUNNING)
17. return -EPERM;
19. if (info->fbops->fb_read) /*没有定义fb_read*/
20. return info->fbops->fb_read(info, buf, count, ppos);
22. total_size = info->screen_size;
24. if (total_size == 0)
25. total_size = info->fix.smem_len;
27. if (p >= total_size)
28. return 0;
30. if (count >= total_size)
31. count = total_size;
33. if (count + p > total_size)
34. count = total_size - p;
36. buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
37. GFP_KERNEL);
38. if (!buffer)
39. return -ENOMEM;
41. src = (u32 __iomem *) (info->screen_base + p);
43. if (info->fbops->fb_sync)
44. info->fbops->fb_sync(info);/*没有定义fb_sync*/
46. while (count) {
47. c = (count > PAGE_SIZE) ? PAGE_SIZE : count;
48. dst = buffer;
49. for (i = c >> 2; i--; )
50. *dst++ = fb_readl(src++);
51. if (c & 3) {
52. u8 *dst8 = (u8 *) dst;
53. u8 __iomem *src8 = (u8 __iomem *) src;
55. for (i = c & 3; i--;)
56. *dst8++ = fb_readb(src8++);
58. src = (u32 __iomem *) src8;
59. }
61. if (copy_to_user(buf, buffer, c)) {
62. err = -EFAULT;
63. break;
64. }
65. *ppos += c;
66. buf += c;
67. cnt += c;
68. count -= c;
69. }
71. kfree(buffer);
73. return (err) ? err : cnt;
74. }
3.4.5 ioctl方法

这里只是简单的看下ioctl方法，这个函数调用很多其他的函数，详细的请自己看吧。

下列代码位于drivers/video/fbmem.c
[cpp] view plain copy
1. static long fb_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
2. {
3. /*获取inode，再获取对应的fb_info*/
4. struct inode *inode = file->f_path.dentry->d_inode;
5. int fbidx = iminor(inode);
6. struct fb_info *info = registered_fb[fbidx];
8. return do_fb_ioctl(info, cmd, arg);
9. }
11. static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
12. unsigned long arg)
13. {
14. struct fb_ops *fb;
15. struct fb_var_screeninfo var;
16. struct fb_fix_screeninfo fix;
17. struct fb_con2fbmap con2fb;
18. struct fb_cmap cmap_from;
19. struct fb_cmap_user cmap;
20. struct fb_event event;
21. void __user *argp = (void __user *)arg;
22. long ret = 0;
24. switch (cmd) {
25. /*获取fb_var_screeninfo*/
26. case FBIOGET_VSCREENINFO:
27. if (!lock_fb_info(info)) /*加锁互斥体info->lock*/
28. return -ENODEV;
29. var = info->var; /*复制var*/
30. unlock_fb_info(info);
32. ret = copy_to_user(argp, &var, sizeof(var)) ? -EFAULT : 0; /*复制var到用户空间*/
33. break;
34. /*设置fb_var_screeninfo*/
35. case FBIOPUT_VSCREENINFO:
36. if (copy_from_user(&var, argp, sizeof(var))) /*从用户空间获取var*/
37. return -EFAULT;
38. if (!lock_fb_info(info))
39. return -ENODEV;
40. acquire_console_sem();
41. info->flags |= FBINFO_MISC_USEREVENT;
42. ret = fb_set_var(info, &var); /*设置var*/
43. info->flags &= ~FBINFO_MISC_USEREVENT;
44. release_console_sem();
45. unlock_fb_info(info);
46. if (!ret && copy_to_user(argp, &var, sizeof(var)))
47. ret = -EFAULT;
48. break;
49. /*获取fb_fix_screeninfo*/ /*fix为不可改变信息，只能获取，不能设置*/
50. case FBIOGET_FSCREENINFO:
51. if (!lock_fb_info(info))
52. return -ENODEV;
53. fix = info->fix;
54. unlock_fb_info(info);
56. ret = copy_to_user(argp, &fix, sizeof(fix)) ? -EFAULT : 0;
57. break;
58. /*设置fb_cmap*/
59. case FBIOPUTCMAP:
60. if (copy_from_user(&cmap, argp, sizeof(cmap)))
61. return -EFAULT;
62. ret = fb_set_user_cmap(&cmap, info); /*设置fb_cmap*/
63. break;
64. /*获取fb_cmap*/
65. case FBIOGETCMAP:
66. if (copy_from_user(&cmap, argp, sizeof(cmap)))
67. return -EFAULT;
68. if (!lock_fb_info(info))
69. return -ENODEV;
70. cmap_from = info->cmap;
71. unlock_fb_info(info);
72. ret = fb_cmap_to_user(&cmap_from, &cmap);/*获取fb_cmp*/
73. break;
74. case FBIOPAN_DISPLAY:
75. if (copy_from_user(&var, argp, sizeof(var)))
76. return -EFAULT;
77. if (!lock_fb_info(info))
78. return -ENODEV;
79. acquire_console_sem();
80. ret = fb_pan_display(info, &var);
81. release_console_sem();
82. unlock_fb_info(info);
83. if (ret == 0 && copy_to_user(argp, &var, sizeof(var)))
84. return -EFAULT;
85. break;
86. case FBIO_CURSOR:
87. ret = -EINVAL;
88. break;
89. case FBIOGET_CON2FBMAP:
90. if (copy_from_user(&con2fb, argp, sizeof(con2fb)))
91. return -EFAULT;
92. if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES)
93. return -EINVAL;
94. con2fb.framebuffer = -1;
95. event.data = &con2fb;
96. if (!lock_fb_info(info))
97. return -ENODEV;
98. event.info = info;
99. fb_notifier_call_chain(FB_EVENT_GET_CONSOLE_MAP, &event);
100. unlock_fb_info(info);
101. ret = copy_to_user(argp, &con2fb, sizeof(con2fb)) ? -EFAULT : 0;
102. break;
103. case FBIOPUT_CON2FBMAP:
104. if (copy_from_user(&con2fb, argp, sizeof(con2fb)))
105. return -EFAULT;
106. if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES)
107. return -EINVAL;
108. if (con2fb.framebuffer < 0 || con2fb.framebuffer >= FB_MAX)
109. return -EINVAL;
110. if (!registered_fb[con2fb.framebuffer])
111. request_module("fb%d", con2fb.framebuffer);
112. if (!registered_fb[con2fb.framebuffer]) {
113. ret = -EINVAL;
114. break;
115. }
116. event.data = &con2fb;
117. if (!lock_fb_info(info))
118. return -ENODEV;
119. event.info = info;
120. ret = fb_notifier_call_chain(FB_EVENT_SET_CONSOLE_MAP, &event);
121. unlock_fb_info(info);
122. break;
123. case FBIOBLANK:
124. if (!lock_fb_info(info))
125. return -ENODEV;
126. acquire_console_sem();
127. info->flags |= FBINFO_MISC_USEREVENT;
128. ret = fb_blank(info, arg); ?*最后调用驱动提供的s3c2410fb_blank*/
129. info->flags &= ~FBINFO_MISC_USEREVENT;
130. release_console_sem();
131. unlock_fb_info(info);
132. break;
133. default:
134. if (!lock_fb_info(info))
135. return -ENODEV;
136. fb = info->fbops;
137. if (fb->fb_ioctl) /*fb_ioctl为空*/
138. ret = fb->fb_ioctl(info, cmd, arg);
139. else
140. ret = -ENOTTY;
141. unlock_fb_info(info);
142. }
143. return ret;
144. }
[cpp] view plain copy
1. static long fb_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
2. {
3. /*获取inode，再获取对应的fb_info*/
4. struct inode *inode = file->f_path.dentry->d_inode;
5. int fbidx = iminor(inode);
6. struct fb_info *info = registered_fb[fbidx];
8. return do_fb_ioctl(info, cmd, arg);
9. }
11. static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
12. unsigned long arg)
13. {
14. struct fb_ops *fb;
15. struct fb_var_screeninfo var;
16. struct fb_fix_screeninfo fix;
17. struct fb_con2fbmap con2fb;
18. struct fb_cmap cmap_from;
19. struct fb_cmap_user cmap;
20. struct fb_event event;
21. void __user *argp = (void __user *)arg;
22. long ret = 0;
24. switch (cmd) {
25. /*获取fb_var_screeninfo*/
26. case FBIOGET_VSCREENINFO:
27. if (!lock_fb_info(info)) /*加锁互斥体info->lock*/
28. return -ENODEV;
29. var = info->var; /*复制var*/
30. unlock_fb_info(info);
32. ret = copy_to_user(argp, &var, sizeof(var)) ? -EFAULT : 0; /*复制var到用户空间*/
33. break;
34. /*设置fb_var_screeninfo*/
35. case FBIOPUT_VSCREENINFO:
36. if (copy_from_user(&var, argp, sizeof(var))) /*从用户空间获取var*/
37. return -EFAULT;
38. if (!lock_fb_info(info))
39. return -ENODEV;
40. acquire_console_sem();
41. info->flags |= FBINFO_MISC_USEREVENT;
42. ret = fb_set_var(info, &var); /*设置var*/
43. info->flags &= ~FBINFO_MISC_USEREVENT;
44. release_console_sem();
45. unlock_fb_info(info);
46. if (!ret && copy_to_user(argp, &var, sizeof(var)))
47. ret = -EFAULT;
48. break;
49. /*获取fb_fix_screeninfo*/ /*fix为不可改变信息，只能获取，不能设置*/
50. case FBIOGET_FSCREENINFO:
51. if (!lock_fb_info(info))
52. return -ENODEV;
53. fix = info->fix;
54. unlock_fb_info(info);
56. ret = copy_to_user(argp, &fix, sizeof(fix)) ? -EFAULT : 0;
57. break;
58. /*设置fb_cmap*/
59. case FBIOPUTCMAP:
60. if (copy_from_user(&cmap, argp, sizeof(cmap)))
61. return -EFAULT;
62. ret = fb_set_user_cmap(&cmap, info); /*设置fb_cmap*/
63. break;
64. /*获取fb_cmap*/
65. case FBIOGETCMAP:
66. if (copy_from_user(&cmap, argp, sizeof(cmap)))
67. return -EFAULT;
68. if (!lock_fb_info(info))
69. return -ENODEV;
70. cmap_from = info->cmap;
71. unlock_fb_info(info);
72. ret = fb_cmap_to_user(&cmap_from, &cmap);/*获取fb_cmp*/
73. break;
74. case FBIOPAN_DISPLAY:
75. if (copy_from_user(&var, argp, sizeof(var)))
76. return -EFAULT;
77. if (!lock_fb_info(info))
78. return -ENODEV;
79. acquire_console_sem();
80. ret = fb_pan_display(info, &var);
81. release_console_sem();
82. unlock_fb_info(info);
83. if (ret == 0 && copy_to_user(argp, &var, sizeof(var)))
84. return -EFAULT;
85. break;
86. case FBIO_CURSOR:
87. ret = -EINVAL;
88. break;
89. case FBIOGET_CON2FBMAP:
90. if (copy_from_user(&con2fb, argp, sizeof(con2fb)))
91. return -EFAULT;
92. if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES)
93. return -EINVAL;
94. con2fb.framebuffer = -1;
95. event.data = &con2fb;
96. if (!lock_fb_info(info))
97. return -ENODEV;
98. event.info = info;
99. fb_notifier_call_chain(FB_EVENT_GET_CONSOLE_MAP, &event);
100. unlock_fb_info(info);
101. ret = copy_to_user(argp, &con2fb, sizeof(con2fb)) ? -EFAULT : 0;
102. break;
103. case FBIOPUT_CON2FBMAP:
104. if (copy_from_user(&con2fb, argp, sizeof(con2fb)))
105. return -EFAULT;
106. if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES)
107. return -EINVAL;
108. if (con2fb.framebuffer < 0 || con2fb.framebuffer >= FB_MAX)
109. return -EINVAL;
110. if (!registered_fb[con2fb.framebuffer])
111. request_module("fb%d", con2fb.framebuffer);
112. if (!registered_fb[con2fb.framebuffer]) {
113. ret = -EINVAL;
114. break;
115. }
116. event.data = &con2fb;
117. if (!lock_fb_info(info))
118. return -ENODEV;
119. event.info = info;
120. ret = fb_notifier_call_chain(FB_EVENT_SET_CONSOLE_MAP, &event);
121. unlock_fb_info(info);
122. break;
123. case FBIOBLANK:
124. if (!lock_fb_info(info))
125. return -ENODEV;
126. acquire_console_sem();
127. info->flags |= FBINFO_MISC_USEREVENT;
128. ret = fb_blank(info, arg); ?*最后调用驱动提供的s3c2410fb_blank*/
129. info->flags &= ~FBINFO_MISC_USEREVENT;
130. release_console_sem();
131. unlock_fb_info(info);
132. break;
133. default:
134. if (!lock_fb_info(info))
135. return -ENODEV;
136. fb = info->fbops;
137. if (fb->fb_ioctl) /*fb_ioctl为空*/
138. ret = fb->fb_ioctl(info, cmd, arg);
139. else
140. ret = -ENOTTY;
141. unlock_fb_info(info);
142. }
143. return ret;
144. }
正如2.2小结所说的，fb_fix_screeninfo只能获取不能设置，因此，ioctl只提供了获取fb_fix_screeninfo的方法，而没有提供设置fb_fix_screeninfo的方法。

3.5 小结

本节对frambuffer的核心层进行了介绍。包括frambuffer子系统的创建，frambuffer的注册和提供给用户空间的5个API函数。下面开始介绍驱动层。

4. 驱动层

本节将开始介绍S3C2440的frambuffer驱动，该驱动源码位于drivers/video/s3c2410fb.c

首先来看下驱动模块的初始化和清除函数。

4.1 s3c2410fb_init和s3c2410fb_cleanup
[cpp] view plain copy
1. static struct platform_driver s3c2410fb_driver = {
2. .probe = s3c2410fb_probe,
3. .remove = s3c2410fb_remove,
4. .suspend = s3c2410fb_suspend,
5. .resume = s3c2410fb_resume,
6. .driver = {
7. .name = "s3c2410-lcd",
8. .owner = THIS_MODULE,
9. },
10. };
12. int __init s3c2410fb_init(void)
13. {
14. int ret = platform_driver_register(&s3c2410fb_driver);
16. if (ret == 0)
17. ret = platform_driver_register(&s3c2412fb_driver);;
19. return ret;
20. }
22. static void __exit s3c2410fb_cleanup(void)
23. {
24. platform_driver_unregister(&s3c2410fb_driver);
25. platform_driver_unregister(&s3c2412fb_driver);
26. }
28. module_init(s3c2410fb_init);
29. module_exit(s3c2410fb_cleanup);
[cpp] view plain copy
1. static struct platform_driver s3c2410fb_driver = {
2. .probe = s3c2410fb_probe,
3. .remove = s3c2410fb_remove,
4. .suspend = s3c2410fb_suspend,
5. .resume = s3c2410fb_resume,
6. .driver = {
7. .name = "s3c2410-lcd",
8. .owner = THIS_MODULE,
9. },
10. };
12. int __init s3c2410fb_init(void)
13. {
14. int ret = platform_driver_register(&s3c2410fb_driver);
16. if (ret == 0)
17. ret = platform_driver_register(&s3c2412fb_driver);;
19. return ret;
20. }
22. static void __exit s3c2410fb_cleanup(void)
23. {
24. platform_driver_unregister(&s3c2410fb_driver);
25. platform_driver_unregister(&s3c2412fb_driver);
26. }
28. module_init(s3c2410fb_init);
29. module_exit(s3c2410fb_cleanup);
当platform_driver_register调用的最后会调用probe方法。接下来就来看看probe方法。

4.2 probe方法
[cpp] view plain copy
1. struct s3c2410fb_info {
2. struct device *dev;
3. struct clk *clk;
5. struct resource *mem;
6. void __iomem *io; /*虚拟地址*/
7. void __iomem *irq_base;
9. enum s3c_drv_type drv_type;
10. struct s3c2410fb_hw regs;
12. unsigned int palette_ready;
14. /* keep these registers in case we need to re-write palette */
15. u32 palette_buffer[256];
16. u32 pseudo_pal[16];
17. };
19. struct s3c2410fb_mach_info {
21. struct s3c2410fb_display *displays; /* attached diplays info */
22. unsigned num_displays; /* number of defined displays */
23. unsigned default_display;
25. /* GPIOs */
27. unsigned long gpcup;
28. unsigned long gpcup_mask;
29. unsigned long gpccon;
30. unsigned long gpccon_mask;
31. unsigned long gpdup;
32. unsigned long gpdup_mask;
33. unsigned long gpdcon;
34. unsigned long gpdcon_mask;
36. /* lpc3600 control register */
37. unsigned long lpcsel;
38. };
40. /* LCD description */
41. struct s3c2410fb_display {
42. /* LCD type */
43. unsigned type;
45. /* Screen size */
46. unsigned short width;
47. unsigned short height;
49. /* Screen info */
50. unsigned short xres;
51. unsigned short yres;
52. unsigned short bpp;
54. unsigned pixclock; /* pixclock in picoseconds */
55. unsigned short left_margin; /* value in pixels (TFT) or HCLKs (STN) */
56. unsigned short right_margin; /* value in pixels (TFT) or HCLKs (STN) */
57. unsigned short hsync_len; /* value in pixels (TFT) or HCLKs (STN) */
58. unsigned short upper_margin; /* value in lines (TFT) or 0 (STN) */
59. unsigned short lower_margin; /* value in lines (TFT) or 0 (STN) */
60. unsigned short vsync_len; /* value in lines (TFT) or 0 (STN) */
62. /* lcd configuration registers */
63. unsigned long lcdcon5;
64. };
66. static int __init s3c24xxfb_probe(struct platform_device *pdev,
67. enum s3c_drv_type drv_type)
68. {
69. struct s3c2410fb_info *info;
70. struct s3c2410fb_display *display;
71. struct fb_info *fbinfo;
72. struct s3c2410fb_mach_info *mach_info;
73. struct resource *res;
74. int ret;
75. int irq;
76. int i;
77. int size;
78. u32 lcdcon1;
79. /*dev.platform_data由函数s3c24xx_fb_set_platdata(mach-smdk2410.c)设置，指向s3c2410fb_mach_info*/
80. mach_info = pdev->dev.platform_data;
81. if (mach_info == NULL) {
82. dev_err(&pdev->dev,
83. "no platform data for lcd, cannot attach ");
84. return -EINVAL;
85. }
86. /*在mach-smdk2440.c中，default_display=0, num_displays=1*/
87. if (mach_info->default_display >= mach_info->num_displays) {
88. dev_err(&pdev->dev, "default is %d but only %d displays ",
89. mach_info->default_display, mach_info->num_displays);
90. return -EINVAL;
91. }
93. display = mach_info->displays + mach_info->default_display;
95. irq = platform_get_irq(pdev, 0); /*获取IRQ号,16号中断*/
96. if (irq < 0) {
97. dev_err(&pdev->dev, "no irq for device ");
98. return -ENOENT;
99. }
100. /*分配struct fb_info 其中包括sizeof字节的私有数据区*/
101. fbinfo = framebuffer_alloc(sizeof(struct s3c2410fb_info), &pdev->dev);
102. if (!fbinfo)
103. return -ENOMEM;
105. platform_set_drvdata(pdev, fbinfo); /*让platform_device->dev.driver_data指向struct fb_info*/
107. info = fbinfo->par; /*par指向s3c2410fb_info*/
108. info->dev = &pdev->dev;
109. info->drv_type = drv_type;
111. res = platform_get_resource(pdev, IORESOURCE_MEM, 0);/*获取平台资源*/
112. if (res == NULL) {
113. dev_err(&pdev->dev, "failed to get memory registers ");
114. ret = -ENXIO;
115. goto dealloc_fb;
116. }
118. size = (res->end - res->start) + 1; /*IO内存申请*/
119. info->mem = request_mem_region(res->start, size, pdev->name);
120. if (info->mem == NULL) {
121. dev_err(&pdev->dev, "failed to get memory region ");
122. ret = -ENOENT;
123. goto dealloc_fb;
124. }
126. info->io = ioremap(res->start, size); /*IO内存映射,获取lcd第一个寄存器的映射地址*/
127. if (info->io == NULL) {
128. dev_err(&pdev->dev, "ioremap() of registers failed ");
129. ret = -ENXIO;
130. goto release_mem;
131. }
132. /*irq_base对应的物理地址是0X4D00 0054(寄存器LCDINTPND)*/
133. info->irq_base = info->io + ((drv_type == DRV_S3C2412) ? S3C2412_LCDINTBASE : S3C2410_LCDINTBASE);
135. dprintk("devinit ");
137. strcpy(fbinfo->fix.id, driver_name); /*复制名字*/
139. /* Stop the video */
140. lcdcon1 = readl(info->io + S3C2410_LCDCON1);
141. writel(lcdcon1 & ~S3C2410_LCDCON1_ENVID, info->io + S3C2410_LCDCON1); /*禁止LCD*/
143. fbinfo->fix.type = FB_TYPE_PACKED_PIXELS;
144. fbinfo->fix.type_aux = 0;
145. fbinfo->fix.xpanstep = 0;
146. fbinfo->fix.ypanstep = 0;
147. fbinfo->fix.ywrapstep = 0;
148. fbinfo->fix.accel = FB_ACCEL_NONE; /* no hardware accelerator */
150. fbinfo->var.nonstd = 0;
151. fbinfo->var.activate = FB_ACTIVATE_NOW;
152. fbinfo->var.accel_flags = 0;
153. fbinfo->var.vmode = FB_VMODE_NONINTERLACED;
155. fbinfo->fbops = &s3c2410fb_ops;
156. fbinfo->flags = FBINFO_FLAG_DEFAULT;
157. fbinfo->pseudo_palette = &info->pseudo_pal;
159. for (i = 0; i < 256; i++)
160. info->palette_buffer[i] = PALETTE_BUFF_CLEAR;
162. ret = request_irq(irq, s3c2410fb_irq, IRQF_DISABLED, pdev->name, info); /*申请IRQ，快速中断*/
163. if (ret) {
164. dev_err(&pdev->dev, "cannot get irq %d - err %d ", irq, ret);
165. ret = -EBUSY;
166. goto release_regs;
167. }
169. info->clk = clk_get(NULL, "lcd"); /*获取时钟信息*/
170. if (!info->clk || IS_ERR(info->clk)) {
171. printk(KERN_ERR "failed to get lcd clock source ");
172. ret = -ENOENT;
173. goto release_irq;
174. }
176. clk_enable(info->clk); /*使能时钟*/
177. dprintk("got and enabled clock ");
179. msleep(1);
181. /* find maximum required memory size for display */
182. /*在多个屏幕中，找出需要的最大memory*/
183. for (i = 0; i < mach_info->num_displays; i++) {
184. unsigned long smem_len = mach_info->displays[i].xres;
185. /*所需的memory空间 = xres * yres * bpp / 8*/
186. smem_len *= mach_info->displays[i].yres;
187. smem_len *= mach_info->displays[i].bpp;
188. smem_len >>= 3;
189. if (fbinfo->fix.smem_len < smem_len)
190. fbinfo->fix.smem_len = smem_len;
191. }
193. /* Initialize video memory */ /*根据上面fix.smem_len的大小，获取DMA映射内存，一致性映射方式*/
194. ret = s3c2410fb_map_video_memory(fbinfo);
195. if (ret) {
196. printk(KERN_ERR "Failed to allocate video RAM: %d ", ret);
197. ret = -ENOMEM;
198. goto release_clock;
199. }
201. dprintk("got video memory ");
203. fbinfo->var.xres = display->xres; /*320*/
204. fbinfo->var.yres = display->yres; /*240*/
205. fbinfo->var.bits_per_pixel = display->bpp; /*16*/
207. s3c2410fb_init_registers(fbinfo); /*LCD寄存器初始化*/
209. s3c2410fb_check_var(&fbinfo->var, fbinfo);
211. ret = register_framebuffer(fbinfo); /*注册framebuffer*/
212. if (ret < 0) {
213. printk(KERN_ERR "Failed to register framebuffer device: %d ",ret);
214. goto free_video_memory;
215. }
217. /* create device files */
218. ret = device_create_file(&pdev->dev, &dev_attr_debug); /*添加设备属性*/
219. if (ret) {
220. printk(KERN_ERR "failed to add debug attribute ");
221. }
223. printk(KERN_INFO "fb%d: %s frame buffer device ",
224. fbinfo->node, fbinfo->fix.id);
226. return 0;
227. /*一旦某个步骤发生错误，以注册的相反顺序开始注销*/
228. free_video_memory:
229. s3c2410fb_unmap_video_memory(fbinfo);
230. release_clock:
231. clk_disable(info->clk);
232. clk_put(info->clk);
233. release_irq:
234. free_irq(irq, info);
235. release_regs:
236. iounmap(info->io);
237. release_mem:
238. release_resource(info->mem);
239. kfree(info->mem);
240. dealloc_fb:
241. platform_set_drvdata(pdev, NULL);
242. framebuffer_release(fbinfo);
243. return ret;
244. }
[cpp] view plain copy
1. struct s3c2410fb_info {
2. struct device *dev;
3. struct clk *clk;
5. struct resource *mem;
6. void __iomem *io; /*虚拟地址*/
7. void __iomem *irq_base;
9. enum s3c_drv_type drv_type;
10. struct s3c2410fb_hw regs;
12. unsigned int palette_ready;
14. /* keep these registers in case we need to re-write palette */
15. u32 palette_buffer[256];
16. u32 pseudo_pal[16];
17. };
19. struct s3c2410fb_mach_info {
21. struct s3c2410fb_display *displays; /* attached diplays info */
22. unsigned num_displays; /* number of defined displays */
23. unsigned default_display;
25. /* GPIOs */
27. unsigned long gpcup;
28. unsigned long gpcup_mask;
29. unsigned long gpccon;
30. unsigned long gpccon_mask;
31. unsigned long gpdup;
32. unsigned long gpdup_mask;
33. unsigned long gpdcon;
34. unsigned long gpdcon_mask;
36. /* lpc3600 control register */
37. unsigned long lpcsel;
38. };
40. /* LCD description */
41. struct s3c2410fb_display {
42. /* LCD type */
43. unsigned type;
45. /* Screen size */
46. unsigned short width;
47. unsigned short height;
49. /* Screen info */
50. unsigned short xres;
51. unsigned short yres;
52. unsigned short bpp;
54. unsigned pixclock; /* pixclock in picoseconds */
55. unsigned short left_margin; /* value in pixels (TFT) or HCLKs (STN) */
56. unsigned short right_margin; /* value in pixels (TFT) or HCLKs (STN) */
57. unsigned short hsync_len; /* value in pixels (TFT) or HCLKs (STN) */
58. unsigned short upper_margin; /* value in lines (TFT) or 0 (STN) */
59. unsigned short lower_margin; /* value in lines (TFT) or 0 (STN) */
60. unsigned short vsync_len; /* value in lines (TFT) or 0 (STN) */
62. /* lcd configuration registers */
63. unsigned long lcdcon5;
64. };
66. static int __init s3c24xxfb_probe(struct platform_device *pdev,
67. enum s3c_drv_type drv_type)
68. {
69. struct s3c2410fb_info *info;
70. struct s3c2410fb_display *display;
71. struct fb_info *fbinfo;
72. struct s3c2410fb_mach_info *mach_info;
73. struct resource *res;
74. int ret;
75. int irq;
76. int i;
77. int size;
78. u32 lcdcon1;
79. /*dev.platform_data由函数s3c24xx_fb_set_platdata(mach-smdk2410.c)设置，指向s3c2410fb_mach_info*/
80. mach_info = pdev->dev.platform_data;
81. if (mach_info == NULL) {
82. dev_err(&pdev->dev,
83. "no platform data for lcd, cannot attach ");
84. return -EINVAL;
85. }
86. /*在mach-smdk2440.c中，default_display=0, num_displays=1*/
87. if (mach_info->default_display >= mach_info->num_displays) {
88. dev_err(&pdev->dev, "default is %d but only %d displays ",
89. mach_info->default_display, mach_info->num_displays);
90. return -EINVAL;
91. }
93. display = mach_info->displays + mach_info->default_display;
95. irq = platform_get_irq(pdev, 0); /*获取IRQ号,16号中断*/
96. if (irq < 0) {
97. dev_err(&pdev->dev, "no irq for device ");
98. return -ENOENT;
99. }
100. /*分配struct fb_info 其中包括sizeof字节的私有数据区*/
101. fbinfo = framebuffer_alloc(sizeof(struct s3c2410fb_info), &pdev->dev);
102. if (!fbinfo)
103. return -ENOMEM;
105. platform_set_drvdata(pdev, fbinfo); /*让platform_device->dev.driver_data指向struct fb_info*/
107. info = fbinfo->par; /*par指向s3c2410fb_info*/
108. info->dev = &pdev->dev;
109. info->drv_type = drv_type;
111. res = platform_get_resource(pdev, IORESOURCE_MEM, 0);/*获取平台资源*/
112. if (res == NULL) {
113. dev_err(&pdev->dev, "failed to get memory registers ");
114. ret = -ENXIO;
115. goto dealloc_fb;
116. }
118. size = (res->end - res->start) + 1; /*IO内存申请*/
119. info->mem = request_mem_region(res->start, size, pdev->name);
120. if (info->mem == NULL) {
121. dev_err(&pdev->dev, "failed to get memory region ");
122. ret = -ENOENT;
123. goto dealloc_fb;
124. }
126. info->io = ioremap(res->start, size); /*IO内存映射,获取lcd第一个寄存器的映射地址*/
127. if (info->io == NULL) {
128. dev_err(&pdev->dev, "ioremap() of registers failed ");
129. ret = -ENXIO;
130. goto release_mem;
131. }
132. /*irq_base对应的物理地址是0X4D00 0054(寄存器LCDINTPND)*/
133. info->irq_base = info->io + ((drv_type == DRV_S3C2412) ? S3C2412_LCDINTBASE : S3C2410_LCDINTBASE);
135. dprintk("devinit ");
137. strcpy(fbinfo->fix.id, driver_name); /*复制名字*/
139. /* Stop the video */
140. lcdcon1 = readl(info->io + S3C2410_LCDCON1);
141. writel(lcdcon1 & ~S3C2410_LCDCON1_ENVID, info->io + S3C2410_LCDCON1); /*禁止LCD*/
143. fbinfo->fix.type = FB_TYPE_PACKED_PIXELS;
144. fbinfo->fix.type_aux = 0;
145. fbinfo->fix.xpanstep = 0;
146. fbinfo->fix.ypanstep = 0;
147. fbinfo->fix.ywrapstep = 0;
148. fbinfo->fix.accel = FB_ACCEL_NONE; /* no hardware accelerator */
150. fbinfo->var.nonstd = 0;
151. fbinfo->var.activate = FB_ACTIVATE_NOW;
152. fbinfo->var.accel_flags = 0;
153. fbinfo->var.vmode = FB_VMODE_NONINTERLACED;
155. fbinfo->fbops = &s3c2410fb_ops;
156. fbinfo->flags = FBINFO_FLAG_DEFAULT;
157. fbinfo->pseudo_palette = &info->pseudo_pal;
159. for (i = 0; i < 256; i++)
160. info->palette_buffer[i] = PALETTE_BUFF_CLEAR;
162. ret = request_irq(irq, s3c2410fb_irq, IRQF_DISABLED, pdev->name, info); /*申请IRQ，快速中断*/
163. if (ret) {
164. dev_err(&pdev->dev, "cannot get irq %d - err %d ", irq, ret);
165. ret = -EBUSY;
166. goto release_regs;
167. }
169. info->clk = clk_get(NULL, "lcd"); /*获取时钟信息*/
170. if (!info->clk || IS_ERR(info->clk)) {
171. printk(KERN_ERR "failed to get lcd clock source ");
172. ret = -ENOENT;
173. goto release_irq;
174. }
176. clk_enable(info->clk); /*使能时钟*/
177. dprintk("got and enabled clock ");
179. msleep(1);
181. /* find maximum required memory size for display */
182. /*在多个屏幕中，找出需要的最大memory*/
183. for (i = 0; i < mach_info->num_displays; i++) {
184. unsigned long smem_len = mach_info->displays[i].xres;
185. /*所需的memory空间 = xres * yres * bpp / 8*/
186. smem_len *= mach_info->displays[i].yres;
187. smem_len *= mach_info->displays[i].bpp;
188. smem_len >>= 3;
189. if (fbinfo->fix.smem_len < smem_len)
190. fbinfo->fix.smem_len = smem_len;
191. }
193. /* Initialize video memory */ /*根据上面fix.smem_len的大小，获取DMA映射内存，一致性映射方式*/
194. ret = s3c2410fb_map_video_memory(fbinfo);
195. if (ret) {
196. printk(KERN_ERR "Failed to allocate video RAM: %d ", ret);
197. ret = -ENOMEM;
198. goto release_clock;
199. }
201. dprintk("got video memory ");
203. fbinfo->var.xres = display->xres; /*320*/
204. fbinfo->var.yres = display->yres; /*240*/
205. fbinfo->var.bits_per_pixel = display->bpp; /*16*/
207. s3c2410fb_init_registers(fbinfo); /*LCD寄存器初始化*/
209. s3c2410fb_check_var(&fbinfo->var, fbinfo);
211. ret = register_framebuffer(fbinfo); /*注册framebuffer*/
212. if (ret < 0) {
213. printk(KERN_ERR "Failed to register framebuffer device: %d ",ret);
214. goto free_video_memory;
215. }
217. /* create device files */
218. ret = device_create_file(&pdev->dev, &dev_attr_debug); /*添加设备属性*/
219. if (ret) {
220. printk(KERN_ERR "failed to add debug attribute ");
221. }
223. printk(KERN_INFO "fb%d: %s frame buffer device ",
224. fbinfo->node, fbinfo->fix.id);
226. return 0;
227. /*一旦某个步骤发生错误，以注册的相反顺序开始注销*/
228. free_video_memory:
229. s3c2410fb_unmap_video_memory(fbinfo);
230. release_clock:
231. clk_disable(info->clk);
232. clk_put(info->clk);
233. release_irq:
234. free_irq(irq, info);
235. release_regs:
236. iounmap(info->io);
237. release_mem:
238. release_resource(info->mem);
239. kfree(info->mem);
240. dealloc_fb:
241. platform_set_drvdata(pdev, NULL);
242. framebuffer_release(fbinfo);
243. return ret;
244. }
这里使用了三个新的数据结构。s3c2410fb_info是驱动程序使用的，里面将保存所有驱动程序所要使用的资源等。而s3c2410fb_display和s3c2410fb_mach_info，是由板级信息，通过platform总线添加到内核中。

s3c2410fb_display中的成员将被复制到fb_var_screeninfo结构中。

该板级信息的定义在arch/arm/mach-s3c2440/mach-smdk2440.c中,来看下
[cpp] view plain copy
1. static struct s3c2410fb_display smdk2440_lcd_cfg __initdata = {
3. .lcdcon5 = S3C2410_LCDCON5_FRM565 |
4. S3C2410_LCDCON5_INVVLINE |
5. S3C2410_LCDCON5_INVVFRAME |
6. S3C2410_LCDCON5_PWREN |
7. S3C2410_LCDCON5_HWSWP,
9. .type = S3C2410_LCDCON1_TFT,
11. .width = 320,//240,
12. .height = 240,//320,
14. .pixclock = 149000,//166667, /* HCLK 60 MHz, divisor 10 */
15. .xres = 320,//240,
16. .yres = 240,//320,
17. .bpp = 16,
18. .left_margin = 20,
19. .right_margin = 38,//8,
20. .hsync_len = 30,//4,
21. .upper_margin = 15,//8,
22. .lower_margin = 12,//7,
23. .vsync_len = 3,//4,
24. };
26. static struct s3c2410fb_mach_info smdk2440_fb_info __initdata = {
27. .displays = &smdk2440_lcd_cfg,
28. .num_displays = 1,
29. .default_display = 0,
31. #if 0
32. /* currently setup by downloader */
33. .gpccon = 0xaa940659,
34. .gpccon_mask = 0xffffffff,
35. .gpcup = 0x0000ffff,
36. .gpcup_mask = 0xffffffff,
37. .gpdcon = 0xaa84aaa0,
38. .gpdcon_mask = 0xffffffff,
39. .gpdup = 0x0000faff,
40. .gpdup_mask = 0xffffffff,
41. #endif
42. //no
43. // .lpcsel = ((0xCE6) & ~7) | 1<<4,
44. };
[cpp] view plain copy
1. static struct s3c2410fb_display smdk2440_lcd_cfg __initdata = {
3. .lcdcon5 = S3C2410_LCDCON5_FRM565 |
4. S3C2410_LCDCON5_INVVLINE |
5. S3C2410_LCDCON5_INVVFRAME |
6. S3C2410_LCDCON5_PWREN |
7. S3C2410_LCDCON5_HWSWP,
9. .type = S3C2410_LCDCON1_TFT,
11. .width = 320,//240,
12. .height = 240,//320,
14. .pixclock = 149000,//166667, /* HCLK 60 MHz, divisor 10 */
15. .xres = 320,//240,
16. .yres = 240,//320,
17. .bpp = 16,
18. .left_margin = 20,
19. .right_margin = 38,//8,
20. .hsync_len = 30,//4,
21. .upper_margin = 15,//8,
22. .lower_margin = 12,//7,
23. .vsync_len = 3,//4,
24. };
26. static struct s3c2410fb_mach_info smdk2440_fb_info __initdata = {
27. .displays = &smdk2440_lcd_cfg,
28. .num_displays = 1,
29. .default_display = 0,
31. #if 0
32. /* currently setup by downloader */
33. .gpccon = 0xaa940659,
34. .gpccon_mask = 0xffffffff,
35. .gpcup = 0x0000ffff,
36. .gpcup_mask = 0xffffffff,
37. .gpdcon = 0xaa84aaa0,
38. .gpdcon_mask = 0xffffffff,
39. .gpdup = 0x0000faff,
40. .gpdup_mask = 0xffffffff,
41. #endif
42. //no
43. // .lpcsel = ((0xCE6) & ~7) | 1<<4,
44. };
这里NOTE：每个LCD屏幕的参数不一样，因此上面的参数会有所不同，这是需要移植的地方。

随后，我们看下在probe方法中调用的几个函数。首先是s3c2410fb_map_video_memory。
[cpp] view plain copy
1. /*
2. * s3c2410fb_map_video_memory():
3. * Allocates the DRAM memory for the frame buffer. This buffer is
4. * remapped into a non-cached, non-buffered, memory region to
5. * allow palette and pixel writes to occur without flushing the
6. * cache. Once this area is remapped, all virtual memory
7. * access to the video memory should occur at the new region.
8. */
9. static int __init s3c2410fb_map_video_memory(struct fb_info *info)
10. {
11. struct s3c2410fb_info *fbi = info->par;
12. dma_addr_t map_dma;
13. unsigned map_size = PAGE_ALIGN(info->fix.smem_len);
15. dprintk("map_video_memory(fbi=%p) map_size %u ", fbi, map_size);
16. /*分配DMA缓冲区，并保存DMA缓冲区虚拟地址*/
17. info->screen_base = dma_alloc_writecombine(fbi->dev, map_size,
18. &map_dma, GFP_KERNEL);
20. if (info->screen_base) {
21. /* prevent initial garbage on screen */
22. dprintk("map_video_memory: clear %p:%08x ",
23. info->screen_base, map_size);
24. memset(info->screen_base, 0x00, map_size); /*DMA缓冲区清0*/
26. info->fix.smem_start = map_dma; /*保存DMA缓冲区物理地址*/
28. dprintk("map_video_memory: dma=%08lx cpu=%p size=%08x ",
29. info->fix.smem_start, info->screen_base, map_size);
30. }
32. return info->screen_base ? 0 : -ENOMEM;
33. }
[cpp] view plain copy
1. /*
2. * s3c2410fb_map_video_memory():
3. * Allocates the DRAM memory for the frame buffer. This buffer is
4. * remapped into a non-cached, non-buffered, memory region to
5. * allow palette and pixel writes to occur without flushing the
6. * cache. Once this area is remapped, all virtual memory
7. * access to the video memory should occur at the new region.
8. */
9. static int __init s3c2410fb_map_video_memory(struct fb_info *info)
10. {
11. struct s3c2410fb_info *fbi = info->par;
12. dma_addr_t map_dma;
13. unsigned map_size = PAGE_ALIGN(info->fix.smem_len);
15. dprintk("map_video_memory(fbi=%p) map_size %u ", fbi, map_size);
16. /*分配DMA缓冲区，并保存DMA缓冲区虚拟地址*/
17. info->screen_base = dma_alloc_writecombine(fbi->dev, map_size,
18. &map_dma, GFP_KERNEL);
20. if (info->screen_base) {
21. /* prevent initial garbage on screen */
22. dprintk("map_video_memory: clear %p:%08x ",
23. info->screen_base, map_size);
24. memset(info->screen_base, 0x00, map_size); /*DMA缓冲区清0*/
26. info->fix.smem_start = map_dma; /*保存DMA缓冲区物理地址*/
28. dprintk("map_video_memory: dma=%08lx cpu=%p size=%08x ",
29. info->fix.smem_start, info->screen_base, map_size);
30. }
32. return info->screen_base ? 0 : -ENOMEM;
33. }
该函数根据fix.smem_len的大小，分配了一个DMA缓冲区，保存了该缓冲区的物理地址和虚拟地址。

接着是s3c2410fb_init_registers：
[cpp] view plain copy
1. /*
2. * s3c2410fb_init_registers - Initialise all LCD-related registers
3. */
4. static int s3c2410fb_init_registers(struct fb_info *info)
5. {
6. struct s3c2410fb_info *fbi = info->par; /*par指向s3c2410fb_info*/
7. struct s3c2410fb_mach_info *mach_info = fbi->dev->platform_data;
8. unsigned long flags;
9. void __iomem *regs = fbi->io;
10. void __iomem *tpal;
11. void __iomem *lpcsel;
13. if (is_s3c2412(fbi)) {
14. tpal = regs + S3C2412_TPAL;
15. lpcsel = regs + S3C2412_TCONSEL;
16. } else {
17. tpal = regs + S3C2410_TPAL;
18. lpcsel = regs + S3C2410_LPCSEL;
19. }
21. /* Initialise LCD with values from haret */
23. local_irq_save(flags); /*禁止所有中断*/
25. /* modify the gpio(s) with interrupts set (bjd) */ /*初始化io管脚*/
27. modify_gpio(S3C2410_GPCUP, mach_info->gpcup, mach_info->gpcup_mask);
28. modify_gpio(S3C2410_GPCCON, mach_info->gpccon, mach_info->gpccon_mask);
29. modify_gpio(S3C2410_GPDUP, mach_info->gpdup, mach_info->gpdup_mask);
30. modify_gpio(S3C2410_GPDCON, mach_info->gpdcon, mach_info->gpdcon_mask);
32. local_irq_restore(flags); /*恢复中断*/
34. dprintk("LPCSEL = 0x%08lx ", mach_info->lpcsel); /*设置TCONSEL，禁止LPC3600*/
35. writel(mach_info->lpcsel, lpcsel);
37. dprintk("replacing TPAL %08x ", readl(tpal));
39. /* ensure temporary palette disabled */
40. writel(0x00, tpal); /*禁止调色板*/
42. return 0;
43. }
45. static inline void modify_gpio(void __iomem *reg,
46. unsigned long set, unsigned long mask)
47. {
48. unsigned long tmp;
50. tmp = readl(reg) & ~mask;
51. writel(tmp | set, reg);
52. }
[cpp] view plain copy
1. /*
2. * s3c2410fb_init_registers - Initialise all LCD-related registers
3. */
4. static int s3c2410fb_init_registers(struct fb_info *info)
5. {
6. struct s3c2410fb_info *fbi = info->par; /*par指向s3c2410fb_info*/
7. struct s3c2410fb_mach_info *mach_info = fbi->dev->platform_data;
8. unsigned long flags;
9. void __iomem *regs = fbi->io;
10. void __iomem *tpal;
11. void __iomem *lpcsel;
13. if (is_s3c2412(fbi)) {
14. tpal = regs + S3C2412_TPAL;
15. lpcsel = regs + S3C2412_TCONSEL;
16. } else {
17. tpal = regs + S3C2410_TPAL;
18. lpcsel = regs + S3C2410_LPCSEL;
19. }
21. /* Initialise LCD with values from haret */
23. local_irq_save(flags); /*禁止所有中断*/
25. /* modify the gpio(s) with interrupts set (bjd) */ /*初始化io管脚*/
27. modify_gpio(S3C2410_GPCUP, mach_info->gpcup, mach_info->gpcup_mask);
28. modify_gpio(S3C2410_GPCCON, mach_info->gpccon, mach_info->gpccon_mask);
29. modify_gpio(S3C2410_GPDUP, mach_info->gpdup, mach_info->gpdup_mask);
30. modify_gpio(S3C2410_GPDCON, mach_info->gpdcon, mach_info->gpdcon_mask);
32. local_irq_restore(flags); /*恢复中断*/
34. dprintk("LPCSEL = 0x%08lx ", mach_info->lpcsel); /*设置TCONSEL，禁止LPC3600*/
35. writel(mach_info->lpcsel, lpcsel);
37. dprintk("replacing TPAL %08x ", readl(tpal));
39. /* ensure temporary palette disabled */
40. writel(0x00, tpal); /*禁止调色板*/
42. return 0;
43. }
45. static inline void modify_gpio(void __iomem *reg,
46. unsigned long set, unsigned long mask)
47. {
48. unsigned long tmp;
50. tmp = readl(reg) & ~mask;
51. writel(tmp | set, reg);
52. }
最后是s3c2410fb_check_var：
[cpp] view plain copy
1. /*
2. * s3c2410fb_check_var():
3. * Get the video params out of 'var'. If a value doesn't fit, round it up,
4. * if it's too big, return -EINVAL.
5. * 检查变量的合法性
6. */
7. static int s3c2410fb_check_var(struct fb_var_screeninfo *var,
8. struct fb_info *info)
9. {
10. struct s3c2410fb_info *fbi = info->par; /*par指向s3c2410fb_info*/
11. struct s3c2410fb_mach_info *mach_info = fbi->dev->platform_data;/*指向s3c2410fb_mach_info*/
12. struct s3c2410fb_display *display = NULL;
13. struct s3c2410fb_display *default_display = mach_info->displays +
14. mach_info->default_display;
15. int type = default_display->type; /*S3C2410_LCDCON1_TFT*/
16. unsigned i;
18. dprintk("check_var(var=%p, info=%p) ", var, info);
20. /* validate x/y resolution */
21. /* choose default mode if possible */ /*var中的成员在probe中设置*/
22. if (var->yres == default_display->yres &&
23. var->xres == default_display->xres &&
24. var->bits_per_pixel == default_display->bpp)
25. display = default_display;
26. else
27. for (i = 0; i < mach_info->num_displays; i++)
28. if (type == mach_info->displays[i].type &&
29. var->yres == mach_info->displays[i].yres &&
30. var->xres == mach_info->displays[i].xres &&
31. var->bits_per_pixel == mach_info->displays[i].bpp) {
32. display = mach_info->displays + i;
33. break;
34. }
36. if (!display) {
37. dprintk("wrong resolution or depth %dx%d at %d bpp ",
38. var->xres, var->yres, var->bits_per_pixel);
39. return -EINVAL;
40. }
42. /* it is always the size as the display */
43. var->xres_virtual = display->xres;
44. var->yres_virtual = display->yres;
45. var->height = display->height;
46. var->width = display->width;
48. /* copy lcd settings */
49. var->pixclock = display->pixclock;
50. var->left_margin = display->left_margin;
51. var->right_margin = display->right_margin;
52. var->upper_margin = display->upper_margin;
53. var->lower_margin = display->lower_margin;
54. var->vsync_len = display->vsync_len;
55. var->hsync_len = display->hsync_len;
57. fbi->regs.lcdcon5 = display->lcdcon5;
58. /* set display type */
59. fbi->regs.lcdcon1 = display->type;
61. var->transp.offset = 0;
62. var->transp.length = 0;
63. /* set r/g/b positions */
64. switch (var->bits_per_pixel) {
65. case 1:
66. case 2:
67. case 4:
68. var->red.offset = 0;
69. var->red.length = var->bits_per_pixel;
70. var->green = var->red;
71. var->blue = var->red;
72. break;
73. case 8:
74. if (display->type != S3C2410_LCDCON1_TFT) {
75. /* 8 bpp 332 */
76. var->red.length = 3;
77. var->red.offset = 5;
78. var->green.length = 3;
79. var->green.offset = 2;
80. var->blue.length = 2;
81. var->blue.offset = 0;
82. } else {
83. var->red.offset = 0;
84. var->red.length = 8;
85. var->green = var->red;
86. var->blue = var->red;
87. }
88. break;
89. case 12:
90. /* 12 bpp 444 */
91. var->red.length = 4;
92. var->red.offset = 8;
93. var->green.length = 4;
94. var->green.offset = 4;
95. var->blue.length = 4;
96. var->blue.offset = 0;
97. break;
99. default:
100. case 16:
101. if (display->lcdcon5 & S3C2410_LCDCON5_FRM565) { /*使用565格式*/
102. /* 16 bpp, 565 format */
103. var->red.offset = 11;
104. var->green.offset = 5;
105. var->blue.offset = 0;
106. var->red.length = 5;
107. var->green.length = 6;
108. var->blue.length = 5;
109. } else {
110. /* 16 bpp, 5551 format */
111. var->red.offset = 11;
112. var->green.offset = 6;
113. var->blue.offset = 1;
114. var->red.length = 5;
115. var->green.length = 5;
116. var->blue.length = 5;
117. }
118. break;
119. case 32:
120. /* 24 bpp 888 and 8 dummy */
121. var->red.length = 8;
122. var->red.offset = 16;
123. var->green.length = 8;
124. var->green.offset = 8;
125. var->blue.length = 8;
126. var->blue.offset = 0;
127. break;
128. }
129. return 0;
130. }
132. /* Interpretation of offset for color fields: All offsets are from the right,
133. * inside a "pixel" value, which is exactly 'bits_per_pixel' wide (means: you
134. * can use the offset as right argument to <<). A pixel afterwards is a bit
135. * stream and is written to video memory as that unmodified.
136. *
137. * For pseudocolor: offset and length should be the same for all color
138. * components. Offset specifies the position of the least significant bit
139. * of the pallette index in a pixel value. Length indicates the number
140. * of available palette entries (i.e. # of entries = 1 << length).
141. */
142. struct fb_bitfield {
143. __u32 offset; /* beginning of bitfield */
144. __u32 length; /* length of bitfield */
145. __u32 msb_right; /* != 0 : Most significant bit is */
146. /* right */
147. };
[cpp] view plain copy
1. /*
2. * s3c2410fb_check_var():
3. * Get the video params out of 'var'. If a value doesn't fit, round it up,
4. * if it's too big, return -EINVAL.
5. * 检查变量的合法性
6. */
7. static int s3c2410fb_check_var(struct fb_var_screeninfo *var,
8. struct fb_info *info)
9. {
10. struct s3c2410fb_info *fbi = info->par; /*par指向s3c2410fb_info*/
11. struct s3c2410fb_mach_info *mach_info = fbi->dev->platform_data;/*指向s3c2410fb_mach_info*/
12. struct s3c2410fb_display *display = NULL;
13. struct s3c2410fb_display *default_display = mach_info->displays +
14. mach_info->default_display;
15. int type = default_display->type; /*S3C2410_LCDCON1_TFT*/
16. unsigned i;
18. dprintk("check_var(var=%p, info=%p) ", var, info);
20. /* validate x/y resolution */
21. /* choose default mode if possible */ /*var中的成员在probe中设置*/
22. if (var->yres == default_display->yres &&
23. var->xres == default_display->xres &&
24. var->bits_per_pixel == default_display->bpp)
25. display = default_display;
26. else
27. for (i = 0; i < mach_info->num_displays; i++)
28. if (type == mach_info->displays[i].type &&
29. var->yres == mach_info->displays[i].yres &&
30. var->xres == mach_info->displays[i].xres &&
31. var->bits_per_pixel == mach_info->displays[i].bpp) {
32. display = mach_info->displays + i;
33. break;
34. }
36. if (!display) {
37. dprintk("wrong resolution or depth %dx%d at %d bpp ",
38. var->xres, var->yres, var->bits_per_pixel);
39. return -EINVAL;
40. }
42. /* it is always the size as the display */
43. var->xres_virtual = display->xres;
44. var->yres_virtual = display->yres;
45. var->height = display->height;
46. var->width = display->width;
48. /* copy lcd settings */
49. var->pixclock = display->pixclock;
50. var->left_margin = display->left_margin;
51. var->right_margin = display->right_margin;
52. var->upper_margin = display->upper_margin;
53. var->lower_margin = display->lower_margin;
54. var->vsync_len = display->vsync_len;
55. var->hsync_len = display->hsync_len;
57. fbi->regs.lcdcon5 = display->lcdcon5;
58. /* set display type */
59. fbi->regs.lcdcon1 = display->type;
61. var->transp.offset = 0;
62. var->transp.length = 0;
63. /* set r/g/b positions */
64. switch (var->bits_per_pixel) {
65. case 1:
66. case 2:
67. case 4:
68. var->red.offset = 0;
69. var->red.length = var->bits_per_pixel;
70. var->green = var->red;
71. var->blue = var->red;
72. break;
73. case 8:
74. if (display->type != S3C2410_LCDCON1_TFT) {
75. /* 8 bpp 332 */
76. var->red.length = 3;
77. var->red.offset = 5;
78. var->green.length = 3;
79. var->green.offset = 2;
80. var->blue.length = 2;
81. var->blue.offset = 0;
82. } else {
83. var->red.offset = 0;
84. var->red.length = 8;
85. var->green = var->red;
86. var->blue = var->red;
87. }
88. break;
89. case 12:
90. /* 12 bpp 444 */
91. var->red.length = 4;
92. var->red.offset = 8;
93. var->green.length = 4;
94. var->green.offset = 4;
95. var->blue.length = 4;
96. var->blue.offset = 0;
97. break;
99. default:
100. case 16:
101. if (display->lcdcon5 & S3C2410_LCDCON5_FRM565) { /*使用565格式*/
102. /* 16 bpp, 565 format */
103. var->red.offset = 11;
104. var->green.offset = 5;
105. var->blue.offset = 0;
106. var->red.length = 5;
107. var->green.length = 6;
108. var->blue.length = 5;
109. } else {
110. /* 16 bpp, 5551 format */
111. var->red.offset = 11;
112. var->green.offset = 6;
113. var->blue.offset = 1;
114. var->red.length = 5;
115. var->green.length = 5;
116. var->blue.length = 5;
117. }
118. break;
119. case 32:
120. /* 24 bpp 888 and 8 dummy */
121. var->red.length = 8;
122. var->red.offset = 16;
123. var->green.length = 8;
124. var->green.offset = 8;
125. var->blue.length = 8;
126. var->blue.offset = 0;
127. break;
128. }
129. return 0;
130. }
132. /* Interpretation of offset for color fields: All offsets are from the right,
133. * inside a "pixel" value, which is exactly 'bits_per_pixel' wide (means: you
134. * can use the offset as right argument to <<). A pixel afterwards is a bit
135. * stream and is written to video memory as that unmodified.
136. *
137. * For pseudocolor: offset and length should be the same for all color
138. * components. Offset specifies the position of the least significant bit
139. * of the pallette index in a pixel value. Length indicates the number
140. * of available palette entries (i.e. # of entries = 1 << length).
141. */
142. struct fb_bitfield {
143. __u32 offset; /* beginning of bitfield */
144. __u32 length; /* length of bitfield */
145. __u32 msb_right; /* != 0 : Most significant bit is */
146. /* right */
147. };
该函数主要将板级信息s3c2410fb_display复制到对应的地方，然后根据RGB的模式设置位域。

4.3 fb_ops方法

在驱动程序中，定义了fb_ops，如下：
[cpp] view plain copy
1. static struct fb_ops s3c2410fb_ops = {
2. .owner = THIS_MODULE,
3. .fb_check_var = s3c2410fb_check_var, /*检查变量的合法性*/
4. .fb_set_par = s3c2410fb_set_par, /*将参数写入LCD控制器，该函数由帧缓冲核心调用*/
5. .fb_blank = s3c2410fb_blank, /*该方法支持显示消隐和去消隐*/
6. .fb_setcolreg = s3c2410fb_setcolreg, /*设置颜色寄存器*/
7. .fb_fillrect = cfb_fillrect, /*用像素行填充矩形框，通用库函数*/
8. .fb_copyarea = cfb_copyarea, /*将屏幕的一个矩形区域复制到另一个区域，通用库函数*/
9. .fb_imageblit = cfb_imageblit, /*显示一副图像，通用库函数*/
10. };
[cpp] view plain copy
1. static struct fb_ops s3c2410fb_ops = {
2. .owner = THIS_MODULE,
3. .fb_check_var = s3c2410fb_check_var, /*检查变量的合法性*/
4. .fb_set_par = s3c2410fb_set_par, /*将参数写入LCD控制器，该函数由帧缓冲核心调用*/
5. .fb_blank = s3c2410fb_blank, /*该方法支持显示消隐和去消隐*/
6. .fb_setcolreg = s3c2410fb_setcolreg, /*设置颜色寄存器*/
7. .fb_fillrect = cfb_fillrect, /*用像素行填充矩形框，通用库函数*/
8. .fb_copyarea = cfb_copyarea, /*将屏幕的一个矩形区域复制到另一个区域，通用库函数*/
9. .fb_imageblit = cfb_imageblit, /*显示一副图像，通用库函数*/
10. };
其中s3c2410fb_check_var在4.2节中已经分析过了，最后三个方法是通用库函数，在这里不作分析。
剩余三个也是驱动程序提供的，现在对这三个程序进行分析。

4.3. 1 s3c2410fb_set_par
[cpp] view plain copy
1. /*
2. * s3c2410fb_set_par - Alters the hardware state.
3. * @info: frame buffer structure that represents a single frame buffer
4. * 根据var中的值设置LCD控制器的寄存器
5. */
6. static int s3c2410fb_set_par(struct fb_info *info)
7. {
8. struct fb_var_screeninfo *var = &info->var;
10. switch (var->bits_per_pixel) {
11. case 32:
12. case 16:
13. case 12:
14. info->fix.visual = FB_VISUAL_TRUECOLOR;
15. break;
16. case 1:
17. info->fix.visual = FB_VISUAL_MONO01;
18. break;
19. default:
20. info->fix.visual = FB_VISUAL_PSEUDOCOLOR;
21. break;
22. }
24. info->fix.line_length = (var->xres_virtual * var->bits_per_pixel) / 8; /* 320*16/8 = 640Bytes */
26. /* activate this new configuration */
28. s3c2410fb_activate_var(info);
29. return 0;
30. }
[cpp] view plain copy
1. /*
2. * s3c2410fb_set_par - Alters the hardware state.
3. * @info: frame buffer structure that represents a single frame buffer
4. * 根据var中的值设置LCD控制器的寄存器
5. */
6. static int s3c2410fb_set_par(struct fb_info *info)
7. {
8. struct fb_var_screeninfo *var = &info->var;
10. switch (var->bits_per_pixel) {
11. case 32:
12. case 16:
13. case 12:
14. info->fix.visual = FB_VISUAL_TRUECOLOR;
15. break;
16. case 1:
17. info->fix.visual = FB_VISUAL_MONO01;
18. break;
19. default:
20. info->fix.visual = FB_VISUAL_PSEUDOCOLOR;
21. break;
22. }
24. info->fix.line_length = (var->xres_virtual * var->bits_per_pixel) / 8; /* 320*16/8 = 640Bytes */
26. /* activate this new configuration */
28. s3c2410fb_activate_var(info);
29. return 0;
30. }
该函数根据像素的位数设置了视觉模式，本例为16为，使用真彩色。然后计算了每行的数据元素大小。共240行。

然后调用了s3c2410fb_activate_var来设置控制器并激活LCD。

s3c2410fb_activate_var函数如下：
[cpp] view plain copy
1. /* s3c2410fb_activate_var
2. *
3. * activate (set) the controller from the given framebuffer
4. * information
5. */
6. static void s3c2410fb_activate_var(struct fb_info *info)
7. {
8. struct s3c2410fb_info *fbi = info->par;
9. void __iomem *regs = fbi->io;
10. int type = fbi->regs.lcdcon1 & S3C2410_LCDCON1_TFT; /*regs.lcdcon1在s3c2410fb_check_var设置*/
11. struct fb_var_screeninfo *var = &info->var;
12. int clkdiv = s3c2410fb_calc_pixclk(fbi, var->pixclock) / 2;
14. dprintk("%s: var->xres = %d ", __func__, var->xres);
15. dprintk("%s: var->yres = %d ", __func__, var->yres);
16. dprintk("%s: var->bpp = %d ", __func__, var->bits_per_pixel);
18. if (type == S3C2410_LCDCON1_TFT) {
19. s3c2410fb_calculate_tft_lcd_regs(info, &fbi->regs);/*根据var，计算出控制寄存器需要设置的值*/
20. --clkdiv;
21. if (clkdiv < 0)
22. clkdiv = 0;
23. } else {
24. s3c2410fb_calculate_stn_lcd_regs(info, &fbi->regs);
25. if (clkdiv < 2)
26. clkdiv = 2;
27. }
29. fbi->regs.lcdcon1 |= S3C2410_LCDCON1_CLKVAL(clkdiv);/*设置CLKVAL*/
31. /* write new registers */
33. dprintk("new register set: ");
34. dprintk("lcdcon[1] = 0x%08lx ", fbi->regs.lcdcon1);
35. dprintk("lcdcon[2] = 0x%08lx ", fbi->regs.lcdcon2);
36. dprintk("lcdcon[3] = 0x%08lx ", fbi->regs.lcdcon3);
37. dprintk("lcdcon[4] = 0x%08lx ", fbi->regs.lcdcon4);
38. dprintk("lcdcon[5] = 0x%08lx ", fbi->regs.lcdcon5);
39. /*把计算好的值填入LCD控制器中*/
40. writel(fbi->regs.lcdcon1 & ~S3C2410_LCDCON1_ENVID,
41. regs + S3C2410_LCDCON1); /*仍然禁止LCD*/
42. writel(fbi->regs.lcdcon2, regs + S3C2410_LCDCON2);
43. writel(fbi->regs.lcdcon3, regs + S3C2410_LCDCON3);
44. writel(fbi->regs.lcdcon4, regs + S3C2410_LCDCON4);
45. writel(fbi->regs.lcdcon5, regs + S3C2410_LCDCON5);
47. /* set lcd address pointers */
48. s3c2410fb_set_lcdaddr(info); /*设置LCD帧缓冲起始地址*/
50. fbi->regs.lcdcon1 |= S3C2410_LCDCON1_ENVID,
51. writel(fbi->regs.lcdcon1, regs + S3C2410_LCDCON1); /*使能LCD*/
52. }
[cpp] view plain copy
1. /* s3c2410fb_activate_var
2. *
3. * activate (set) the controller from the given framebuffer
4. * information
5. */
6. static void s3c2410fb_activate_var(struct fb_info *info)
7. {
8. struct s3c2410fb_info *fbi = info->par;
9. void __iomem *regs = fbi->io;
10. int type = fbi->regs.lcdcon1 & S3C2410_LCDCON1_TFT; /*regs.lcdcon1在s3c2410fb_check_var设置*/
11. struct fb_var_screeninfo *var = &info->var;
12. int clkdiv = s3c2410fb_calc_pixclk(fbi, var->pixclock) / 2;
14. dprintk("%s: var->xres = %d ", __func__, var->xres);
15. dprintk("%s: var->yres = %d ", __func__, var->yres);
16. dprintk("%s: var->bpp = %d ", __func__, var->bits_per_pixel);
18. if (type == S3C2410_LCDCON1_TFT) {
19. s3c2410fb_calculate_tft_lcd_regs(info, &fbi->regs);/*根据var，计算出控制寄存器需要设置的值*/
20. --clkdiv;
21. if (clkdiv < 0)
22. clkdiv = 0;
23. } else {
24. s3c2410fb_calculate_stn_lcd_regs(info, &fbi->regs);
25. if (clkdiv < 2)
26. clkdiv = 2;
27. }
29. fbi->regs.lcdcon1 |= S3C2410_LCDCON1_CLKVAL(clkdiv);/*设置CLKVAL*/
31. /* write new registers */
33. dprintk("new register set: ");
34. dprintk("lcdcon[1] = 0x%08lx ", fbi->regs.lcdcon1);
35. dprintk("lcdcon[2] = 0x%08lx ", fbi->regs.lcdcon2);
36. dprintk("lcdcon[3] = 0x%08lx ", fbi->regs.lcdcon3);
37. dprintk("lcdcon[4] = 0x%08lx ", fbi->regs.lcdcon4);
38. dprintk("lcdcon[5] = 0x%08lx ", fbi->regs.lcdcon5);
39. /*把计算好的值填入LCD控制器中*/
40. writel(fbi->regs.lcdcon1 & ~S3C2410_LCDCON1_ENVID,
41. regs + S3C2410_LCDCON1); /*仍然禁止LCD*/
42. writel(fbi->regs.lcdcon2, regs + S3C2410_LCDCON2);
43. writel(fbi->regs.lcdcon3, regs + S3C2410_LCDCON3);
44. writel(fbi->regs.lcdcon4, regs + S3C2410_LCDCON4);
45. writel(fbi->regs.lcdcon5, regs + S3C2410_LCDCON5);
47. /* set lcd address pointers */
48. s3c2410fb_set_lcdaddr(info); /*设置LCD帧缓冲起始地址*/
50. fbi->regs.lcdcon1 |= S3C2410_LCDCON1_ENVID,
51. writel(fbi->regs.lcdcon1, regs + S3C2410_LCDCON1); /*使能LCD*/
52. }
其中调用的三个函数如下：
[cpp] view plain copy
1. static unsigned int s3c2410fb_calc_pixclk(struct s3c2410fb_info *fbi,
2. unsigned long pixclk)
3. {
4. unsigned long clk = clk_get_rate(fbi->clk); /*获取当前时钟频率(Hz)*/
5. unsigned long long div;
7. /* pixclk is in picoseconds, our clock is in Hz
8. *
9. * Hz -> picoseconds is / 10^-12
10. */
12. div = (unsigned long long)clk * pixclk;
13. div >>= 12; /* div / 2^12 */
14. do_div(div, 625 * 625UL * 625); /* div / 5^12 */
16. dprintk("pixclk %ld, divisor is %ld ", pixclk, (long)div);
17. return div;
18. }
20. /* s3c2410fb_calculate_tft_lcd_regs
21. *
22. * calculate register values from var settings
23. */
24. static void s3c2410fb_calculate_tft_lcd_regs(const struct fb_info *info,
25. struct s3c2410fb_hw *regs)
26. {
27. const struct s3c2410fb_info *fbi = info->par;
28. const struct fb_var_screeninfo *var = &info->var;
30. switch (var->bits_per_pixel) {
31. case 1:
32. regs->lcdcon1 |= S3C2410_LCDCON1_TFT1BPP;
33. break;
34. case 2:
35. regs->lcdcon1 |= S3C2410_LCDCON1_TFT2BPP;
36. break;
37. case 4:
38. regs->lcdcon1 |= S3C2410_LCDCON1_TFT4BPP;
39. break;
40. case 8:
41. regs->lcdcon1 |= S3C2410_LCDCON1_TFT8BPP;
42. regs->lcdcon5 |= S3C2410_LCDCON5_BSWP |
43. S3C2410_LCDCON5_FRM565;
44. regs->lcdcon5 &= ~S3C2410_LCDCON5_HWSWP;
45. break;
46. case 16:
47. regs->lcdcon1 |= S3C2410_LCDCON1_TFT16BPP;
48. regs->lcdcon5 &= ~S3C2410_LCDCON5_BSWP;
49. regs->lcdcon5 |= S3C2410_LCDCON5_HWSWP;
50. break;
51. case 32:
52. regs->lcdcon1 |= S3C2410_LCDCON1_TFT24BPP;
53. regs->lcdcon5 &= ~(S3C2410_LCDCON5_BSWP |
54. S3C2410_LCDCON5_HWSWP |
55. S3C2410_LCDCON5_BPP24BL);
56. break;
57. default:
58. /* invalid pixel depth */
59. dev_err(fbi->dev, "invalid bpp %d ",
60. var->bits_per_pixel);
61. }
62. /* update X/Y info */
63. dprintk("setting vert: up=%d, low=%d, sync=%d ",
64. var->upper_margin, var->lower_margin, var->vsync_len);
66. dprintk("setting horz: lft=%d, rt=%d, sync=%d ",
67. var->left_margin, var->right_margin, var->hsync_len);
68. /*
69. 所有时序参数必须减1，因为在公式中:
70. Frame Rate = 1/ [ { (VSPW+1) + (VBPD+1) + (LIINEVAL + 1) + (VFPD+1) } x {(HSPW+1) + (HBPD +1)
71. + (HFPD+1) + (HOZVAL + 1) } x { 2 x ( CLKVAL+1 ) / ( HCLK ) } ]
72. */
73. regs->lcdcon2 = S3C2410_LCDCON2_LINEVAL(var->yres - 1) |
74. S3C2410_LCDCON2_VBPD(var->upper_margin - 1) |
75. S3C2410_LCDCON2_VFPD(var->lower_margin - 1) |
76. S3C2410_LCDCON2_VSPW(var->vsync_len - 1);
78. regs->lcdcon3 = S3C2410_LCDCON3_HBPD(var->right_margin - 1) |
79. S3C2410_LCDCON3_HFPD(var->left_margin - 1) |
80. S3C2410_LCDCON3_HOZVAL(var->xres - 1);
82. regs->lcdcon4 = S3C2410_LCDCON4_HSPW(var->hsync_len - 1);
83. }
85. /* s3c2410fb_set_lcdaddr
86. *
87. * initialise lcd controller address pointers
88. */
89. static void s3c2410fb_set_lcdaddr(struct fb_info *info)
90. {
91. unsigned long saddr1, saddr2, saddr3;
92. struct s3c2410fb_info *fbi = info->par;
93. void __iomem *regs = fbi->io;
95. saddr1 = info->fix.smem_start >> 1; /*帧缓冲区起始地址*/
96. saddr2 = info->fix.smem_start;
97. saddr2 += info->fix.line_length * info->var.yres;
98. saddr2 >>= 1; /*帧缓冲区结束地址*/
100. saddr3 = S3C2410_OFFSIZE(0) |
101. S3C2410_PAGEWIDTH((info->fix.line_length / 2) & 0x3ff); /*offset = 0, pagewidth = 320*/
103. dprintk("LCDSADDR1 = 0x%08lx ", saddr1);
104. dprintk("LCDSADDR2 = 0x%08lx ", saddr2);
105. dprintk("LCDSADDR3 = 0x%08lx ", saddr3);
107. writel(saddr1, regs + S3C2410_LCDSADDR1);
108. writel(saddr2, regs + S3C2410_LCDSADDR2);
109. writel(saddr3, regs + S3C2410_LCDSADDR3);
110. }
[cpp] view plain copy
1. static unsigned int s3c2410fb_calc_pixclk(struct s3c2410fb_info *fbi,
2. unsigned long pixclk)
3. {
4. unsigned long clk = clk_get_rate(fbi->clk); /*获取当前时钟频率(Hz)*/
5. unsigned long long div;
7. /* pixclk is in picoseconds, our clock is in Hz
8. *
9. * Hz -> picoseconds is / 10^-12
10. */
12. div = (unsigned long long)clk * pixclk;
13. div >>= 12; /* div / 2^12 */
14. do_div(div, 625 * 625UL * 625); /* div / 5^12 */
16. dprintk("pixclk %ld, divisor is %ld ", pixclk, (long)div);
17. return div;
18. }
20. /* s3c2410fb_calculate_tft_lcd_regs
21. *
22. * calculate register values from var settings
23. */
24. static void s3c2410fb_calculate_tft_lcd_regs(const struct fb_info *info,
25. struct s3c2410fb_hw *regs)
26. {
27. const struct s3c2410fb_info *fbi = info->par;
28. const struct fb_var_screeninfo *var = &info->var;
30. switch (var->bits_per_pixel) {
31. case 1:
32. regs->lcdcon1 |= S3C2410_LCDCON1_TFT1BPP;
33. break;
34. case 2:
35. regs->lcdcon1 |= S3C2410_LCDCON1_TFT2BPP;
36. break;
37. case 4:
38. regs->lcdcon1 |= S3C2410_LCDCON1_TFT4BPP;
39. break;
40. case 8:
41. regs->lcdcon1 |= S3C2410_LCDCON1_TFT8BPP;
42. regs->lcdcon5 |= S3C2410_LCDCON5_BSWP |
43. S3C2410_LCDCON5_FRM565;
44. regs->lcdcon5 &= ~S3C2410_LCDCON5_HWSWP;
45. break;
46. case 16:
47. regs->lcdcon1 |= S3C2410_LCDCON1_TFT16BPP;
48. regs->lcdcon5 &= ~S3C2410_LCDCON5_BSWP;
49. regs->lcdcon5 |= S3C2410_LCDCON5_HWSWP;
50. break;
51. case 32:
52. regs->lcdcon1 |= S3C2410_LCDCON1_TFT24BPP;
53. regs->lcdcon5 &= ~(S3C2410_LCDCON5_BSWP |
54. S3C2410_LCDCON5_HWSWP |
55. S3C2410_LCDCON5_BPP24BL);
56. break;
57. default:
58. /* invalid pixel depth */
59. dev_err(fbi->dev, "invalid bpp %d ",
60. var->bits_per_pixel);
61. }
62. /* update X/Y info */
63. dprintk("setting vert: up=%d, low=%d, sync=%d ",
64. var->upper_margin, var->lower_margin, var->vsync_len);
66. dprintk("setting horz: lft=%d, rt=%d, sync=%d ",
67. var->left_margin, var->right_margin, var->hsync_len);
68. /*
69. 所有时序参数必须减1，因为在公式中:
70. Frame Rate = 1/ [ { (VSPW+1) + (VBPD+1) + (LIINEVAL + 1) + (VFPD+1) } x {(HSPW+1) + (HBPD +1)
71. + (HFPD+1) + (HOZVAL + 1) } x { 2 x ( CLKVAL+1 ) / ( HCLK ) } ]
72. */
73. regs->lcdcon2 = S3C2410_LCDCON2_LINEVAL(var->yres - 1) |
74. S3C2410_LCDCON2_VBPD(var->upper_margin - 1) |
75. S3C2410_LCDCON2_VFPD(var->lower_margin - 1) |
76. S3C2410_LCDCON2_VSPW(var->vsync_len - 1);
78. regs->lcdcon3 = S3C2410_LCDCON3_HBPD(var->right_margin - 1) |
79. S3C2410_LCDCON3_HFPD(var->left_margin - 1) |
80. S3C2410_LCDCON3_HOZVAL(var->xres - 1);
82. regs->lcdcon4 = S3C2410_LCDCON4_HSPW(var->hsync_len - 1);
83. }
85. /* s3c2410fb_set_lcdaddr
86. *
87. * initialise lcd controller address pointers
88. */
89. static void s3c2410fb_set_lcdaddr(struct fb_info *info)
90. {
91. unsigned long saddr1, saddr2, saddr3;
92. struct s3c2410fb_info *fbi = info->par;
93. void __iomem *regs = fbi->io;
95. saddr1 = info->fix.smem_start >> 1; /*帧缓冲区起始地址*/
96. saddr2 = info->fix.smem_start;
97. saddr2 += info->fix.line_length * info->var.yres;
98. saddr2 >>= 1; /*帧缓冲区结束地址*/
100. saddr3 = S3C2410_OFFSIZE(0) |
101. S3C2410_PAGEWIDTH((info->fix.line_length / 2) & 0x3ff); /*offset = 0, pagewidth = 320*/
103. dprintk("LCDSADDR1 = 0x%08lx ", saddr1);
104. dprintk("LCDSADDR2 = 0x%08lx ", saddr2);
105. dprintk("LCDSADDR3 = 0x%08lx ", saddr3);
107. writel(saddr1, regs + S3C2410_LCDSADDR1);
108. writel(saddr2, regs + S3C2410_LCDSADDR2);
109. writel(saddr3, regs + S3C2410_LCDSADDR3);
110. }
s3c2410fb_calc_pixclk用于计算时钟频率。

s3c2410fb_calculate_tft_lcd_regs设置了LCD的控制寄存器。

s3c2410fb_set_lcdaddr设置了LCD的地址寄存器，该寄存器的设置请参考datasheet。

4.3. 2 s3c2410fb_blank

该方法完成消隐功能。
[cpp] view plain copy
1. /*
2. * s3c2410fb_blank
3. * @blank_mode: the blank mode we want.
4. * @info: frame buffer structure that represents a single frame buffer
5. *
6. * Blank the screen if blank_mode != 0, else unblank. Return 0 if
7. * blanking succeeded, != 0 if un-/blanking failed due to e.g. a
8. * video mode which doesn't support it. Implements VESA suspend
9. * and powerdown modes on hardware that supports disabling hsync/vsync:
10. *
11. * Returns negative errno on error, or zero on success.
12. *
13. */
14. static int s3c2410fb_blank(int blank_mode, struct fb_info *info)
15. {
16. struct s3c2410fb_info *fbi = info->par;
17. void __iomem *tpal_reg = fbi->io;
19. dprintk("blank(mode=%d, info=%p) ", blank_mode, info);
21. tpal_reg += is_s3c2412(fbi) ? S3C2412_TPAL : S3C2410_TPAL;
23. if (blank_mode == FB_BLANK_POWERDOWN) { /*消隐*/
24. s3c2410fb_lcd_enable(fbi, 0); /*禁止LCD*/
25. } else {
26. s3c2410fb_lcd_enable(fbi, 1); /*启动LCD*/
27. }
29. if (blank_mode == FB_BLANK_UNBLANK) /*去消隐*/
30. writel(0x0, tpal_reg); /*禁止temporary palette*/
31. else { /*消隐*/
32. dprintk("setting TPAL to output 0x000000 ");
33. writel(S3C2410_TPAL_EN, tpal_reg); /*使能temporary palette，颜色为黑色*/
34. }
36. return 0;
37. }
[cpp] view plain copy
1. /*
2. * s3c2410fb_blank
3. * @blank_mode: the blank mode we want.
4. * @info: frame buffer structure that represents a single frame buffer
5. *
6. * Blank the screen if blank_mode != 0, else unblank. Return 0 if
7. * blanking succeeded, != 0 if un-/blanking failed due to e.g. a
8. * video mode which doesn't support it. Implements VESA suspend
9. * and powerdown modes on hardware that supports disabling hsync/vsync:
10. *
11. * Returns negative errno on error, or zero on success.
12. *
13. */
14. static int s3c2410fb_blank(int blank_mode, struct fb_info *info)
15. {
16. struct s3c2410fb_info *fbi = info->par;
17. void __iomem *tpal_reg = fbi->io;
19. dprintk("blank(mode=%d, info=%p) ", blank_mode, info);
21. tpal_reg += is_s3c2412(fbi) ? S3C2412_TPAL : S3C2410_TPAL;
23. if (blank_mode == FB_BLANK_POWERDOWN) { /*消隐*/
24. s3c2410fb_lcd_enable(fbi, 0); /*禁止LCD*/
25. } else {
26. s3c2410fb_lcd_enable(fbi, 1); /*启动LCD*/
27. }
29. if (blank_mode == FB_BLANK_UNBLANK) /*去消隐*/
30. writel(0x0, tpal_reg); /*禁止temporary palette*/
31. else { /*消隐*/
32. dprintk("setting TPAL to output 0x000000 ");
33. writel(S3C2410_TPAL_EN, tpal_reg); /*使能temporary palette，颜色为黑色*/
34. }
36. return 0;
37. }
在消隐时，屏幕将全黑。

4.3.3 s3c2410fb_setcolreg

该函数的功能用于设置LCD的调色板。调色板的概念请看我的转帖：LCD调色板。
[cpp] view plain copy
1. static int s3c2410fb_setcolreg(unsigned regno,
2. unsigned red, unsigned green, unsigned blue,
3. unsigned transp, struct fb_info *info)
4. {
5. struct s3c2410fb_info *fbi = info->par; /*par指向s3c2410fb_info*/
6. void __iomem *regs = fbi->io;
7. unsigned int val;
9. /* dprintk("setcol: regno=%d, rgb=%d,%d,%d ",
10. regno, red, green, blue); */
12. switch (info->fix.visual) {
13. case FB_VISUAL_TRUECOLOR: /*使用真彩色*/
14. /* true-colour, use pseudo-palette */
16. if (regno < 16) { /*16种颜色，为什么只用16种颜色???????????*/
17. u32 *pal = info->pseudo_palette;
19. val = chan_to_field(red, &info->var.red);
20. val |= chan_to_field(green, &info->var.green);
21. val |= chan_to_field(blue, &info->var.blue);
23. pal[regno] = val; /*保存颜色值*/
24. }
25. break;
27. case FB_VISUAL_PSEUDOCOLOR:
28. if (regno < 256) {
29. /* currently assume RGB 5-6-5 mode */
31. val = (red >> 0) & 0xf800;
32. val |= (green >> 5) & 0x07e0;
33. val |= (blue >> 11) & 0x001f;
35. writel(val, regs + S3C2410_TFTPAL(regno));
36. schedule_palette_update(fbi, regno, val);
37. }
39. break;
41. default:
42. return 1; /* unknown type */
43. }
45. return 0;
46. }
47. /* from pxafb.c */
48. static inline unsigned int chan_to_field(unsigned int chan,
49. struct fb_bitfield *bf)
50. {
51. /*下面用到的length和offset在s3c2410fb_check_var函数中设置*/
52. chan &= 0xffff; /*取低16位*/
53. chan >>= 16 - bf->length; /*取第length为到16位为有效位*/
54. return chan << bf->offset; /*移动到相应的位置。*/
55. }
[cpp] view plain copy
1. static int s3c2410fb_setcolreg(unsigned regno,
2. unsigned red, unsigned green, unsigned blue,
3. unsigned transp, struct fb_info *info)
4. {
5. struct s3c2410fb_info *fbi = info->par; /*par指向s3c2410fb_info*/
6. void __iomem *regs = fbi->io;
7. unsigned int val;
9. /* dprintk("setcol: regno=%d, rgb=%d,%d,%d ",
10. regno, red, green, blue); */
12. switch (info->fix.visual) {
13. case FB_VISUAL_TRUECOLOR: /*使用真彩色*/
14. /* true-colour, use pseudo-palette */
16. if (regno < 16) { /*16种颜色，为什么只用16种颜色???????????*/
17. u32 *pal = info->pseudo_palette;
19. val = chan_to_field(red, &info->var.red);
20. val |= chan_to_field(green, &info->var.green);
21. val |= chan_to_field(blue, &info->var.blue);
23. pal[regno] = val; /*保存颜色值*/
24. }
25. break;
27. case FB_VISUAL_PSEUDOCOLOR:
28. if (regno < 256) {
29. /* currently assume RGB 5-6-5 mode */
31. val = (red >> 0) & 0xf800;
32. val |= (green >> 5) & 0x07e0;
33. val |= (blue >> 11) & 0x001f;
35. writel(val, regs + S3C2410_TFTPAL(regno));
36. schedule_palette_update(fbi, regno, val);
37. }
39. break;
41. default:
42. return 1; /* unknown type */
43. }
45. return 0;
46. }
47. /* from pxafb.c */
48. static inline unsigned int chan_to_field(unsigned int chan,
49. struct fb_bitfield *bf)
50. {
51. /*下面用到的length和offset在s3c2410fb_check_var函数中设置*/
52. chan &= 0xffff; /*取低16位*/
53. chan >>= 16 - bf->length; /*取第length为到16位为有效位*/
54. return chan << bf->offset; /*移动到相应的位置。*/
55. }
我们使用的是真彩色，可以设置16种颜色，颜色的位域值通过调用chan_to_field获得，然后保存了颜色的值。但是比较奇怪的是，这里并没有将值保存到0x4d000400为起始的内存中，不知为何。反而倒是在伪彩色模式下，使用了writel(val, regs + S3C2410_TFTPAL(regno))写到内存中，然后调用schedule_palette_update函数来更新palette表。我们来看下。
[cpp] view plain copy
1. static void schedule_palette_update(struct s3c2410fb_info *fbi,
2. unsigned int regno, unsigned int val)
3. {
4. unsigned long flags;
5. unsigned long irqen;
6. void __iomem *irq_base = fbi->irq_base;
8. local_irq_save(flags);
10. fbi->palette_buffer[regno] = val;
12. if (!fbi->palette_ready) {
13. fbi->palette_ready = 1;
15. /* enable IRQ */
16. irqen = readl(irq_base + S3C24XX_LCDINTMSK);
17. irqen &= ~S3C2410_LCDINT_FRSYNC;
18. writel(irqen, irq_base + S3C24XX_LCDINTMSK);
19. }
21. local_irq_restore(flags);
22. }
[cpp] view plain copy
1. static void schedule_palette_update(struct s3c2410fb_info *fbi,
2. unsigned int regno, unsigned int val)
3. {
4. unsigned long flags;
5. unsigned long irqen;
6. void __iomem *irq_base = fbi->irq_base;
8. local_irq_save(flags);
10. fbi->palette_buffer[regno] = val;
12. if (!fbi->palette_ready) {
13. fbi->palette_ready = 1;
15. /* enable IRQ */
16. irqen = readl(irq_base + S3C24XX_LCDINTMSK);
17. irqen &= ~S3C2410_LCDINT_FRSYNC;
18. writel(irqen, irq_base + S3C24XX_LCDINTMSK);
19. }
21. local_irq_restore(flags);
22. }
这个函数的作用就是开启了LCD的帧同步中断，这个中断在VSYNC信号从无效变成有效时产生。当中断产生时，会调用在probe方法中注册的ISR。ISR如下：
[cpp] view plain copy
1. static irqreturn_t s3c2410fb_irq(int irq, void *dev_id)
2. {
3. struct s3c2410fb_info *fbi = dev_id;
4. void __iomem *irq_base = fbi->irq_base;
5. unsigned long lcdirq = readl(irq_base + S3C24XX_LCDINTPND);
6. b
7. if (lcdirq & S3C2410_LCDINT_FRSYNC) {
8. if (fbi->palette_ready)
9. s3c2410fb_write_palette(fbi);
11. writel(S3C2410_LCDINT_FRSYNC, irq_base + S3C24XX_LCDINTPND);
12. writel(S3C2410_LCDINT_FRSYNC, irq_base + S3C24XX_LCDSRCPND);
13. }
15. return IRQ_HANDLED;
16. }
18. static void s3c2410fb_write_palette(struct s3c2410fb_info *fbi)
19. {
20. unsigned int i;
21. void __iomem *regs = fbi->io;
23. fbi->palette_ready = 0; /*清除ready标志*/
25. for (i = 0; i < 256; i++) {
26. unsigned long ent = fbi->palette_buffer[i];
27. if (ent == PALETTE_BUFF_CLEAR)
28. continue;
30. writel(ent, regs + S3C2410_TFTPAL(i));
32. /* it seems the only way to know exactly
33. * if the palette wrote ok, is to check
34. * to see if the value verifies ok
35. */
37. if (readw(regs + S3C2410_TFTPAL(i)) == ent)
38. fbi->palette_buffer[i] = PALETTE_BUFF_CLEAR;
39. else
40. fbi->palette_ready = 1; /* retry */
41. }
42. }
[cpp] view plain copy
1. static irqreturn_t s3c2410fb_irq(int irq, void *dev_id)
2. {
3. struct s3c2410fb_info *fbi = dev_id;
4. void __iomem *irq_base = fbi->irq_base;
5. unsigned long lcdirq = readl(irq_base + S3C24XX_LCDINTPND);
6. b
7. if (lcdirq & S3C2410_LCDINT_FRSYNC) {
8. if (fbi->palette_ready)
9. s3c2410fb_write_palette(fbi);
11. writel(S3C2410_LCDINT_FRSYNC, irq_base + S3C24XX_LCDINTPND);
12. writel(S3C2410_LCDINT_FRSYNC, irq_base + S3C24XX_LCDSRCPND);
13. }
15. return IRQ_HANDLED;
16. }
18. static void s3c2410fb_write_palette(struct s3c2410fb_info *fbi)
19. {
20. unsigned int i;
21. void __iomem *regs = fbi->io;
23. fbi->palette_ready = 0; /*清除ready标志*/
25. for (i = 0; i < 256; i++) {
26. unsigned long ent = fbi->palette_buffer[i];
27. if (ent == PALETTE_BUFF_CLEAR)
28. continue;
30. writel(ent, regs + S3C2410_TFTPAL(i));
32. /* it seems the only way to know exactly
33. * if the palette wrote ok, is to check
34. * to see if the value verifies ok
35. */
37. if (readw(regs + S3C2410_TFTPAL(i)) == ent)
38. fbi->palette_buffer[i] = PALETTE_BUFF_CLEAR;
39. else
40. fbi->palette_ready = 1; /* retry */
41. }
42. }
在中断函数中调用了s3c2410fb_write_palette，该函数对写入内存的颜色值进行检查。如果确认其已经写入，则将palette_buffer中的清除，否则retry。

5. 总结

本文对frambuffer子系统做了简单的介绍。frambuffer子系统的函数相当之多，在这里是不可能一一介绍的。本文首先介绍了主要的数据结构，

随后分析了frambuffer核心层，在核心层简单的分析了5个API函数，接着，对驱动层做了介绍，驱动层的大多数函数都给出了分析。
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原文地址：https://www.cnblogs.com/zzb-Dream-90Time/p/7301057.html

Framebuffer子系统【转】

1. 概述

2. 数据结构

2.1 fb_info 结构

2.2 fb_fix_screeninfo结构

2.3 fb_var_screeninfo结构

2.4 fb_ops结构

3. frambuffer核心层

3.1 fbmem_init和fbmem_exit

3.2 framebuffer_alloc

3.3 register_framebuffer

3.4 字符设备方法

3.4.1 open方法

3.4.2 release方法

3.4.3 write方法

3.4.4 read方法

3.4.5 ioctl方法

3.5 小结

4. 驱动层

4.1 s3c2410fb_init和s3c2410fb_cleanup

4.2 probe方法

4.3 fb_ops方法

4.3. 1 s3c2410fb_set_par

4.3. 2 s3c2410fb_blank

4.3.3 s3c2410fb_setcolreg

5. 总结