字符设备驱动（1）代码分析---之gpio_to_irq

---

/**************************************************************
gpio_to_irq(S5PV210_GPH2(0))
**************************************************************/
#define gpio_to_irq      __gpio_to_irq

int __gpio_to_irq(unsigned gpio)
{
    struct gpio_chip    *chip;
    chip = gpio_to_chip(S5PV210_GPH2(0));

static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
{
    return gpio_desc[S5PV210_GPH2(0)].chip; 
    //参考gpio-s5pv210.c中
    //samsung_gpiolib_add_4bit_chips(s5pv210_gpio_4bit, nr_chips)函数
    //gpio_desc[id].chip = chip;
}

    return chip->to_irq ? chip->to_irq(chip, gpio - chip->base) : -ENXIO;
    //s5pv210_gpio_4bit
}

int samsung_gpiolib_to_irq(struct gpio_chip *chip, unsigned int offset)
{
//获得gpio_chip结构体所在的父结构体s3c_gpio_chip的指针 
struct s3c_gpio_chip *s3c_chip = container_of(chip,struct s3c_gpio_chip, chip);
//获取虚拟映射机制中定义的终端号
    return s3c_chip->irq_base + offset;

#define IRQ_EINT(x)        ((x) < 16 ? ((x) + S5P_EINT_BASE1) 
                    : ((x) - 16 + S5P_EINT_BASE2))
#define S5P_EINT_BASE2        (IRQ_VIC_END + 1)
#define IRQ_VIC_END        S5P_IRQ_VIC3(31)
#define S5P_IRQ_VIC3(x)        (S5P_VIC3_BASE + (x))
#define S5P_VIC3_BASE        S5P_IRQ(96)
#define S5P_IRQ(x)        ((x) + S5P_IRQ_OFFSET)
#define S5P_IRQ_OFFSET        (32)

#define S5P_EINT_BASE1        (S5P_IRQ_VIC0(0))
#define S5P_IRQ_VIC0(x)        (S5P_VIC0_BASE + (x))
#define S5P_VIC0_BASE        S5P_IRQ(0)

}

static struct s3c_gpio_chip s5pv210_gpio_4bit[] = {
    
    {
        .chip    = {
            .base    = S5PV210_GPA0(0),
            .ngpio    = S5PV210_GPIO_A0_NR,
            .label    = "GPA0",
        },
    }, 
    ...............
    ...............
    {
     .base    = (S5P_VA_GPIO + 0xC40),
     .config    = &gpio_cfg_noint,
     .irq_base = IRQ_EINT(16),
     .chip    = {
        .base    = S5PV210_GPH2(0),
        .ngpio    = S5PV210_GPIO_H2_NR,
        .label    = "GPH2",
        .to_irq = samsung_gpiolib_to_irq,
        },
    }, 
    
    {
        .base    = (S5P_VA_GPIO + 0xC60),
        .config    = &gpio_cfg_noint,
        .irq_base = IRQ_EINT(24),
        .chip    = {
            .base    = S5PV210_GPH3(0),
            .ngpio    = S5PV210_GPIO_H3_NR,
            .label    = "GPH3",
            .to_irq = samsung_gpiolib_to_irq,
        },
    },
};

static __init int s5pv210_gpiolib_init(void)
{
    struct s3c_gpio_chip *chip = s5pv210_gpio_4bit;
    int nr_chips = ARRAY_SIZE(s5pv210_gpio_4bit);

for (i = 0; i < nr_chips; i++, chip++) {
        if (chip->config == NULL) {
            chip->config = &gpio_cfg;
            chip->group = gpioint_group++;
        }
        if (chip->base == NULL)
            chip->base = S5PV210_BANK_BASE(i);
    }

    samsung_gpiolib_add_4bit_chips(s5pv210_gpio_4bit, nr_chips);

void  __init samsung_gpiolib_add_4bit_chips(struct s3c_gpio_chip *chip,
                       int nr_chips)
{
        for (; nr_chips > 0; nr_chips--, chip++)
        {
            samsung_gpiolib_add_4bit(chip);

void __init samsung_gpiolib_add_4bit(struct s3c_gpio_chip *chip)
            {
                    chip->chip.direction_input = samsung_gpiolib_4bit_input;
                    chip->chip.direction_output = samsung_gpiolib_4bit_output;
                    chip->pm = __gpio_pm(&s3c_gpio_pm_4bit);
            }

            s3c_gpiolib_add(chip); 

    __init void s3c_gpiolib_add(struct s3c_gpio_chip *chip)
            {

　　　　　　　　　　//将s3c_gpio_chip 结构体变量s5pv210_gpio_4bit数组中的每一个数组变量 ".chip"传递给gpio_chip结构体指针gc

　　　　　　　　　　struct gpio_chip *gc = &chip->chip; 
　　　　　　　　　//gc    = {
                //    .base    = S5PV210_GPH2(0),
                //    .ngpio    = S5PV210_GPIO_H2_NR,
                //    .label    = "GPH2",
                //    .to_irq = samsung_gpiolib_to_irq,
                //    },
                int ret;
                spin_lock_init(&chip->lock);
　　　　　　　　　　//给gc结构体指针其他结构体成员赋值
                if (!gc->direction_input)
                    gc->direction_input = s3c_gpiolib_input;
                if (!gc->direction_output)
                    gc->direction_output = s3c_gpiolib_output;
                if (!gc->set)
                    gc->set = s3c_gpiolib_set;
                if (!gc->get)
                    gc->get = s3c_gpiolib_get;

            #ifdef CONFIG_PM
                if (chip->pm != NULL) {
                    if (!chip->pm->save || !chip->pm->resume)
                        printk(KERN_ERR "gpio: %s has missing PM functions
",
                               gc->label);
                } else
                    printk(KERN_ERR "gpio: %s has no PM function
", gc->label);
            #endif

                // gpiochip_add() prints own failure message on error.
                ret = gpiochip_add(gc);

int gpiochip_add(struct gpio_chip *chip){   
 unsigned long    flags;    int        status = 0;    unsigned    id;

int        base = chip->base; //base = S5PV210_GPH2(0)
　　//查看获得的gpio_chip结构体指针基址和范围是否在有效范围之内
    if ((!gpio_is_valid(base) || !gpio_is_valid(base + chip->ngpio - 1))
            && base >= 0) {
        status = -EINVAL;
        goto fail;
    }

    spin_lock_irqsave(&gpio_lock, flags);

    if (base < 0) {
        base = gpiochip_find_base(chip->ngpio);
        if (base < 0) {
            status = base;
            goto unlock;
        }
        chip->base = base;
    }

    //these GPIO numbers must not be managed by another gpio_chip 
    //遍历某个GPIO端口组的所有IO，如：S5PV210_GPH2端口组的8个IO口S5PV210_GPH2(0)~(7)
　
　　for (id = base; id < base + chip->ngpio; id++) 
　　{

 　　//正常状态gpio_desc[base].chip未被初始化，所以各个成员为NULL
　　　　if (gpio_desc[id].chip != NULL) {
            status = -EBUSY;
            break;
        }
    }
  if (status == 0) {
     for (id = base; id < base + chip->ngpio; id++) {
            gpio_desc[id].chip = chip;
//至此完成gpio_desc[S5PV210_GPH2(0)].chip的赋值，作为返回值在gpio_to_chip()中返回

            // REVISIT:  most hardware initializes GPIOs as
             * inputs (often with pullups enabled) so power
             * usage is minimized.  Linux code should set the
             * gpio direction first thing; but until it does,
             * we may expose the wrong direction in sysfs.
             
            gpio_desc[id].flags = !chip->direction_input
                ? (1 << FLAG_IS_OUT)
                : 0;
        }
    }

    of_gpiochip_add(chip);

unlock:
    spin_unlock_irqrestore(&gpio_lock, flags);

    if (status)
        goto fail;

    status = gpiochip_export(chip);
    if (status)
        goto fail;

    return 0;
fail:
     //failures here can mean systems won't boot... 
    pr_err("gpiochip_add: gpios %d..%d (%s) failed to register
",
        chip->base, chip->base + chip->ngpio - 1,
        chip->label ? : "generic");
    return status;
}

if (ret >= 0)
                    s3c_gpiolib_track(chip)

            }

        }
}

    s5p_register_gpioint_bank(IRQ_GPIOINT, 0, S5P_GPIOINT_GROUP_MAXNR);

    return 0;
}