目标：
1. 完成最终的设备驱动，增加具体的watchdog设备操作的代码。
测试代码：
代码最终实现见cwd_demo.c
代码只实现了read与write. 没有实现ioctl.
因此，我们可以通过shell指令直接操作我们的watchdog.
read函数，只读取watchdog的0x01 和0x02寄存器。
write函数无论写入多少个字节，驱动实际只写第一个字节。
1. 编译
$ make
2. 装载驱动
$ sudo insmod cwd_demo.ko
3.查看设备
$ sudo ls /dev/cdw_demo -l
crw------- 1 root root 10, 171 6月 30 18:38 /dev/cdw_demo
生成一个主设备号为10， 次设备号为171的设备。
4. 读取设备信息
$ sudo cat /dev/cdw_demo
B
5. 操作设备
此操作需要使用root用户
# sudo echo 'a' > /dev/cdw_demo #激活watchdog
# sudo echo 't' > /dev/cdw_demo # 喂狗
# sudo echo 'd' > /dev/cdw_demo # 停止停止设备
6. 卸载驱动 $ sudo rmmod cwd_demo
7. 查看log记录
$ tail -f -n 30 /var/log/syslog
8. 使用python操作
$ su
# python
>>> f = open("/dev/cwd_demo", "w+") #打开
>>> f.write("a"); f.flush() #激活watchdog
>>> f.write("t"); f.flush() # 喂狗
>>> f.write("d"); f.flush() # 停止watchdog
>>> f.readlines(); f.seek(0, 0) # 读外设的寄存器
['Bx00
']
>>> f.close() #关闭外设
>>>
代码：
cwd_demo.c
1 #include <linux/init.h> //初始换函数 2 #include <linux/kernel.h> //内核头文件 3 #include <linux/module.h> //模块的头文件 4 #include <linux/pci.h> 5 #include <linux/miscdevice.h> 6 #include <linux/types.h> 7 #include <linux/fs.h> 8 #include <linux/mm.h> 9 #include <linux/watchdog.h> 10 #include <linux/ioport.h> 11 #include <linux/uaccess.h> 12 #include <linux/io.h> 13 14 15 16 #define CWD_MODULE_NAME "cstl watchdog" 17 18 /* We only use 1 card for cwd_demo */ 19 static int cards_found; 20 static struct pci_dev *cwd_pci; 21 22 MODULE_LICENSE("GPL"); 23 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR); 24 25 #define CWD_VERSION "0.1" 26 #define PCI_VENDOR_ID_REDHAT 0x1af4 27 #define PCI_DEVICE_ID_CWD 0x0101 28 29 /* Memory mapped registers */ 30 #define CWD_EXPECT_CLOSE_REG (io + 0x00) /* make no sense, read is 0x42*/ 31 #define CWD_ACTIVATE_REG (io + 0x01) 32 #define CWD_TRIGER_REG (io + 0x02) 33 34 /* internal variables */ 35 static void __iomem *BASEADDR; 36 static resource_size_t io; 37 38 /* 39 * Kernel Interfaces 40 */ 41 42 static ssize_t cwd_write(struct file *file, const char __user *data, 43 size_t len, loff_t *ppos) 44 { 45 /* See if we got the magic character 'V' and reload the timer */ 46 char c; 47 char cwd_expect_close = inb(CWD_EXPECT_CLOSE_REG); 48 if (cwd_expect_close != 0x42){ 49 printk(KERN_ERR "failed to request the magic character, %d ", cwd_expect_close); 50 return -EFAULT; 51 } 52 printk(KERN_ALERT "Hello, I'm cwd_demo %d ", cwd_expect_close); 53 /* only support one character one time write. ignore len */ 54 if (get_user(c, data + 0)) 55 return -EFAULT; 56 printk(KERN_ALERT "Hello, cwd_demo is writing %d ", c); 57 if (c == 'a') { // 58 printk(KERN_ALERT "cwd_demo activates watchdog "); 59 outb(0x03, CWD_ACTIVATE_REG); 60 } 61 if (c == 'd') {// 62 printk(KERN_ALERT "cwd_demo deactivates watchdog "); 63 outb(0x00, CWD_ACTIVATE_REG); 64 } 65 if (c == 't') {// 66 printk(KERN_ALERT "cwd_demo feeds watchdog "); 67 outb(0x32, CWD_TRIGER_REG); 68 } 69 return len; 70 } 71 72 static ssize_t cwd_read(struct file *file, char __user *buffer, 73 size_t count, loff_t *ppos) 74 { 75 char data[3]; 76 int retval = 0; 77 if (*ppos >= 3) 78 goto out; 79 else if (*ppos + count > 3) 80 count = 3 - *ppos; 81 printk(KERN_ALERT "in read, ppos is %d, count is %d ", *ppos, count); 82 data[0] = inb(CWD_EXPECT_CLOSE_REG); 83 if (data[0] != 0x42){ 84 printk(KERN_ERR "failed to request the magic character, 0x%x ", data[0]); 85 return -EFAULT; 86 } 87 printk(KERN_ALERT "Hello, I'm cwd_demo 0x%x ", data[0]); 88 data[1] = inb(CWD_ACTIVATE_REG); 89 printk(KERN_ALERT "Hello, this is the second char 0x%x ", data[1]); 90 data[2] = 10; 91 if (copy_to_user(buffer, data, count)){ 92 printk(KERN_ALERT "in read, copy to read failed "); 93 retval = -EFAULT; 94 goto out; 95 } 96 *ppos += count; 97 retval = count; 98 out: 99 return retval; 100 } 101 102 static loff_t cwd_llseek(struct file *file, loff_t offset, int whence) 103 { 104 file->f_pos = 0; 105 return file->f_pos; 106 } 107 static int cwd_open(struct inode *inode, struct file *file) 108 { 109 // return nonseekable_open(inode, file); 110 return 0; 111 } 112 113 static int cwd_release(struct inode *inode, struct file *file) 114 { 115 /* Shut off the timer. */ 116 char activate = 0x1; 117 outb(0x00, CWD_ACTIVATE_REG); 118 activate = inb(CWD_ACTIVATE_REG); 119 if (activate != 0x00){ 120 printk(KERN_CRIT 121 "Unexpected close, not stopping watchdog! "); 122 } 123 return 0; 124 } 125 126 static const struct file_operations cwd_fops = { 127 .owner = THIS_MODULE, 128 .llseek = cwd_llseek, 129 .write = cwd_write, 130 .read = cwd_read, 131 // .unlocked_ioctl = cwd_ioctl, 132 .open = cwd_open, 133 .release = cwd_release, 134 }; 135 136 static struct miscdevice cwd_miscdev = { 137 // .minor = WATCHDOG_MINOR, 138 .minor = 171, 139 .name = "cwd_demo", 140 .fops = &cwd_fops, 141 }; 142 143 144 /* 145 * Data for PCI driver interface 146 */ 147 static DEFINE_PCI_DEVICE_TABLE(cwd_pci_tbl) = { 148 { PCI_DEVICE(PCI_VENDOR_ID_REDHAT, PCI_DEVICE_ID_CWD), }, 149 { 0, }, /* End of list */ 150 }; 151 MODULE_DEVICE_TABLE(pci, cwd_pci_tbl); 152 153 154 static unsigned char cwd_getdevice(struct pci_dev *pdev) 155 { 156 unsigned int addr = 0; 157 if (pci_enable_device(pdev)) { 158 printk(KERN_ERR "failed to enable device "); 159 goto err_devput; 160 } 161 162 if (pci_resource_start(pdev, 0) == 0x0000) { 163 printk(KERN_ERR "No I/O-Address for card detected "); 164 goto err_disable; 165 } 166 167 if (pci_request_region(pdev, 0, CWD_MODULE_NAME)) { 168 printk(KERN_ERR "failed to request region "); 169 goto err_disable; 170 } 171 172 // BASEADDR = pci_ioremap_bar(pdev, 0); 173 // BASEADDR = ioremap(pci_resource_start(pdev, 0), pci_resource_len(pdev, 0)); 174 // if (BASEADDR == NULL) { 175 // /* Something's wrong here, BASEADDR has to be set */ 176 // printk(KERN_ERR "failed to get BASEADDR "); 177 // goto err_release; 178 // } 179 180 /* here we are testing it is a io space or mem space */ 181 // pci_write_config_dword(pdev, 0x10, 0xc090); 182 pci_read_config_dword(pdev, 0x10, &addr); 183 184 io = pci_resource_start(pdev, 0); 185 printk(KERN_ERR "base addr 0 is 0x%x ", inb(io)); 186 printk(KERN_ERR "success to get BASEADDR: 0x%x ", addr); 187 188 /* Done */ 189 cwd_pci = pdev; 190 return 1; 191 192 err_release: 193 pci_release_region(pdev, 0); 194 err_disable: 195 pci_disable_device(pdev); 196 err_devput: 197 return 0; 198 } 199 200 201 static int cwd_probe(struct pci_dev *pdev, 202 const struct pci_device_id *ent) 203 { 204 int ret; 205 static int major, minor; 206 cards_found++; 207 if (cards_found == 1) 208 printk(KERN_INFO "Cstl WatchDog Timer Driver v%s ", 209 CWD_VERSION); 210 211 if (cards_found > 1) { 212 printk(KERN_ERR "Cstl driver only supports 1 device "); 213 return -ENODEV; 214 } 215 216 /* Check whether or not the hardware watchdog is there */ 217 if (!cwd_getdevice(pdev) || cwd_pci == NULL) 218 return -ENODEV; 219 /* Register the watchdog so that userspace has access to it */ 220 ret = misc_register(&cwd_miscdev); 221 // major = MAJOR(cwd_miscdev); 222 // minor = MINOR(cwd_miscdev); 223 // printk(KERN_ERR "register miscdev on major=%d minor=%d ", 224 // MAJOR(cwd_miscdev), MINOR(cwd_miscdev)); 225 printk(KERN_ERR "register miscdev on minor=%d ", WATCHDOG_MINOR); 226 if (ret != 0) { 227 printk(KERN_ERR 228 "cannot register miscdev on minor=%d (err=%d) ", 229 WATCHDOG_MINOR, ret); 230 goto err_unmap; 231 } 232 printk(KERN_INFO 233 "initialized cstl watchdog (0x%x).", (unsigned int)io); 234 return 0; 235 err_unmap: 236 iounmap(BASEADDR); 237 pci_release_region(cwd_pci, 0); 238 pci_disable_device(cwd_pci); 239 cwd_pci = NULL; 240 return ret; 241 242 } 243 244 static int cwd_timer_stop(void) 245 { 246 /* Returns 0 if the timer was disabled, non-zero otherwise */ 247 return 0; 248 } 249 250 static void cwd_remove(struct pci_dev *pdev) 251 { 252 /* Stop the timer before we leave */ 253 cwd_timer_stop(); 254 255 /* Deregister */ 256 misc_deregister(&cwd_miscdev); 257 // iounmap(BASEADDR); 258 pci_release_region(cwd_pci, 0); 259 pci_disable_device(cwd_pci); 260 cwd_pci = NULL; 261 } 262 263 static void cwd_shutdown(struct pci_dev *pdev) 264 { 265 cwd_timer_stop(); 266 } 267 268 269 static struct pci_driver cwd_driver = { 270 .name = CWD_MODULE_NAME, 271 .id_table = cwd_pci_tbl, 272 .probe = cwd_probe, 273 .remove = cwd_remove, 274 .shutdown = cwd_shutdown, 275 }; 276 277 static int __init cwd_demo_start(void) 278 { 279 printk(KERN_ALERT "Loading cwd_demo module... "); 280 printk(KERN_ALERT "Hello, I'm cwd_demo "); 281 return pci_register_driver(&cwd_driver); 282 } 283 284 static void __exit cwd_demo_end(void) 285 { 286 pci_unregister_driver(&cwd_driver); 287 printk(KERN_ALERT "cwd demo Module Unloaded, Goodbye! "); 288 289 } 290 291 module_init(cwd_demo_start); 292 module_exit(cwd_demo_end);
Makefile
1 ifeq ($(KERNELRELEASE),) 2 KVERSION = $(shell uname -r) 3 all: 4 make -C /lib/modules/$(KVERSION)/build M=$(shell pwd) modules 5 echo $(shell pwd) 6 clean: 7 make -C /lib/modules/$(KVERSION)/build M=$(shell pwd) clean 8 else 9 obj-m :=cwd_demo.o 10 endif