Linux Platform设备驱动学习与小结
浏览数：20 /
时间：2015年06月20日
Platform 设备先被注册然后platfrom驱动加载时会调用驱动程序中的probe（）入口函数，扫描系统中已注册的设备，通过。Name域找到匹配设备后将驱动和设备绑定。一个驱动可以对应多个设备，但是一个设备只对一个驱动。Linux下的虚拟总线platform对应设备platform_device，对应的驱动为platform_driver。一个很不恰当的例子：设备好比男人，驱动好比女人，platform作为媒人，将两个对上眼的（name域相同）的相匹配到一起。然后男人（device）到她（driver）的门口（driver的probe入口函数）主动去找女人约会巴拉巴拉啪啪啪。。。哎呀好羞射，这就进入正题：
/********************************************************************************* * Copyright: (C) 2011 Guo Wenxue<[email protected]> * All rights reserved. * * Filename: s3c_led.c * Description: This is the common LED driver runs on S3C24XX. * * Version: 1.0.0(10/27/2011~) * Author: Guo Wenxue <[email protected]> * ChangeLog: 1, Release initial version on "10/27/2011 11:39:10 AM" * ********************************************************************************/ #include "s3c_driver.h" #define DRV_AUTHOR "Guo Wenxue <[email protected]>" #define DRV_DESC "S3C24XX LED driver" /* Driver version*/ #define DRV_MAJOR_VER 1 #define DRV_MINOR_VER 0 #define DRV_REVER_VER 0 #define DEV_NAME DEV_LED_NAME //#define DEV_MAJOR DEV_LED_MAJOR #ifndef DEV_MAJOR #define DEV_MAJOR 0 /* dynamic major by default */ #endif #define TIMER_TIMEOUT 40 static int debug = DISABLE; static int dev_major = DEV_MAJOR; static int dev_minor = 0; /* ============================ Platform Device part ===============================*/ /* LED hardware informtation structure*/ struct s3c_led_info { unsigned char num; /* The LED number */ unsigned int gpio; /* Which GPIO the LED used */ unsigned char active_level; /* The GPIO pin level(HIGHLEVEL or LOWLEVEL) to turn on or off */ unsigned char status; /* Current LED status: OFF/ON */ unsigned char blink; /* Blink or not */ }; /* The LED platform device private data structure */ struct s3c_led_platform_data { struct s3c_led_info *leds; int nleds; }; /* LED hardware informtation data*/ static struct s3c_led_info s3c_leds[] = { [0] = { .num = 1, .gpio = S3C2410_GPB(5), .active_level = LOWLEVEL, .status = OFF, .blink = ENABLE, }, [1] = { .num = 2, .gpio = S3C2410_GPB(6), .active_level = LOWLEVEL, .status = OFF, .blink = DISABLE, }, [2] = { .num = 3, .gpio = S3C2410_GPB(8), .active_level = LOWLEVEL, .status = OFF, .blink = DISABLE, }, [3] = { .num = 4, .gpio = S3C2410_GPB(10), .active_level = LOWLEVEL, .status = OFF, .blink = DISABLE, }, }; /* The LED platform device private data */ static struct s3c_led_platform_data s3c_led_data = { .leds = s3c_leds, .nleds = ARRAY_SIZE(s3c_leds), }; struct led_device { struct s3c_led_platform_data *data; struct cdev cdev; struct class *dev_class; struct timer_list blink_timer; } led_device; static void platform_led_release(struct device * dev) { int i; struct s3c_led_platform_data *pdata = dev->platform_data; dbg_print("%s():%d\n", __FUNCTION__,__LINE__); /* Turn all LED off */ for(i=0; i<pdata->nleds; i++) { s3c2410_gpio_setpin(pdata->leds[i].gpio, ~pdata->leds[i].active_level); } } static struct platform_device s3c_led_device = { .name = "s3c_led", .id = 1, .dev = { .platform_data = &s3c_led_data, .release = platform_led_release, }, }; /* ===================== led device driver part ===========================*/ void led_timer_handler(unsigned long data) { int i; struct s3c_led_platform_data *pdata = (struct s3c_led_platform_data *)data; for(i=0; i<pdata->nleds; i++) { if(ON == pdata->leds[i].status) { s3c2410_gpio_setpin(pdata->leds[i].gpio, pdata->leds[i].active_level); } else { s3c2410_gpio_setpin(pdata->leds[i].gpio, ~pdata->leds[i].active_level); } if(ENABLE == pdata->leds[i].blink ) /* LED should blink */ { /* Switch status between 0 and 1 to turn LED ON or off */ pdata->leds[i].status = pdata->leds[i].status ^ 0x01; } mod_timer(&(led_device.blink_timer), jiffies + TIMER_TIMEOUT); } } static int led_open(struct inode *inode, struct file *file) { struct led_device *pdev ; struct s3c_led_platform_data *pdata; pdev = container_of(inode->i_cdev,struct led_device, cdev); pdata = pdev->data; file->private_data = pdata; return 0; } static int led_release(struct inode *inode, struct file *file) { return 0; } static void print_led_help(void) { printk("Follow is the ioctl() command for LED driver:\n"); printk("Enable Driver debug command: %u\n", SET_DRV_DEBUG); printk("Get Driver verion command : %u\n", GET_DRV_VER); printk("Turn LED on command : %u\n", LED_ON); printk("Turn LED off command : %u\n", LED_OFF); printk("Turn LED blink command : %u\n", LED_BLINK); } /* compatible with kernel version >=2.6.38*/ static long led_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { struct s3c_led_platform_data *pdata = file->private_data; switch (cmd) { case SET_DRV_DEBUG: dbg_print("%s driver debug now.\n", DISABLE == arg ? "Disable" : "Enable"); debug = (0==arg) ? DISABLE : ENABLE; break; case GET_DRV_VER: print_version(DRV_VERSION); return DRV_VERSION; case LED_OFF: if(pdata->nleds <= arg) { printk("LED%ld doesn't exist\n", arg); return -ENOTTY; } pdata->leds[arg].status = OFF; pdata->leds[arg].blink = DISABLE; break; case LED_ON: if(pdata->nleds <= arg) { printk("LED%ld doesn't exist\n", arg); return -ENOTTY; } pdata->leds[arg].status = ON; pdata->leds[arg].blink = DISABLE; break; case LED_BLINK: if(pdata->nleds <= arg) { printk("LED%ld doesn't exist\n", arg); return -ENOTTY; } pdata->leds[arg].blink = ENABLE; pdata->leds[arg].status = ON; break; default: dbg_print("%s driver don't support ioctl command=%d\n", DEV_NAME, cmd); print_led_help(); return -EINVAL; } return 0; } static struct file_operations led_fops = { .owner = THIS_MODULE, .open = led_open, .release = led_release, .unlocked_ioctl = led_ioctl, /* compatible with kernel version >=2.6.38*/ }; static int s3c_led_probe(struct platform_device *dev) { struct s3c_led_platform_data *pdata = dev->dev.platform_data; int result = 0; int i; dev_t devno; /* Initialize the LED status */ for(i=0; i<pdata->nleds; i++) { s3c2410_gpio_cfgpin(pdata->leds[i].gpio, S3C2410_GPIO_OUTPUT); if(ON == pdata->leds[i].status) { s3c2410_gpio_setpin(pdata->leds[i].gpio, pdata->leds[i].active_level); } else { s3c2410_gpio_setpin(pdata->leds[i].gpio, ~pdata->leds[i].active_level); } } /* Alloc the device for driver */ if (0 != dev_major) { devno = MKDEV(dev_major, dev_minor); result = register_chrdev_region(devno, 1, DEV_NAME); } else { result = alloc_chrdev_region(&devno, dev_minor, 1, DEV_NAME); dev_major = MAJOR(devno); } /* Alloc for device major failure */ if (result < 0) { printk("%s driver can't get major %d\n", DEV_NAME, dev_major); return result; } /* Initialize button structure and register cdev*/ memset(&led_device, 0, sizeof(led_device)); led_device.data = dev->dev.platform_data; cdev_init (&(led_device.cdev), &led_fops); led_device.cdev.owner = THIS_MODULE; result = cdev_add (&(led_device.cdev), devno , 1); if (result) { printk (KERN_NOTICE "error %d add %s device", result, DEV_NAME); goto ERROR; } led_device.dev_class = class_create(THIS_MODULE, DEV_NAME); if(IS_ERR(led_device.dev_class)) { printk("%s driver create class failture\n",DEV_NAME); result = -ENOMEM; goto ERROR; } #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,24) device_create(led_device.dev_class, NULL, devno, NULL, DEV_NAME); #else device_create (led_device.dev_class, NULL, devno, DEV_NAME); #endif /* Initial the LED blink timer */ init_timer(&(led_device.blink_timer)); led_device.blink_timer.function = led_timer_handler; led_device.blink_timer.data = (unsigned long)pdata; led_device.blink_timer.expires = jiffies + TIMER_TIMEOUT; add_timer(&(led_device.blink_timer)); printk("S3C %s driver version %d.%d.%d initiliazed.\n", DEV_NAME, DRV_MAJOR_VER, DRV_MINOR_VER, DRV_REVER_VER); return 0; ERROR: printk("S3C %s driver version %d.%d.%d install failure.\n", DEV_NAME, DRV_MAJOR_VER, DRV_MINOR_VER, DRV_REVER_VER); cdev_del(&(led_device.cdev)); unregister_chrdev_region(devno, 1); return result; } static int s3c_led_remove(struct platform_device *dev) { dev_t devno = MKDEV(dev_major, dev_minor); del_timer(&(led_device.blink_timer)); cdev_del(&(led_device.cdev)); device_destroy(led_device.dev_class, devno); class_destroy(led_device.dev_class); unregister_chrdev_region(devno, 1); printk("S3C %s driver removed\n", DEV_NAME); return 0; } static struct platform_driver s3c_led_driver = { .probe = s3c_led_probe, .remove = s3c_led_remove, .driver = { .name = "s3c_led", .owner = THIS_MODULE, }, }; static int __init s3c_led_init(void) { int ret = 0; ret = platform_device_register(&s3c_led_device); if(ret) { printk(KERN_ERR "%s:%d: Can't register platform device %d\n", __FUNCTION__,__LINE__, ret); goto fail_reg_plat_dev; } dbg_print("Regist S3C LED Platform Device successfully.\n"); ret = platform_driver_register(&s3c_led_driver); if(ret) { printk(KERN_ERR "%s:%d: Can't register platform driver %d\n", __FUNCTION__,__LINE__, ret); goto fail_reg_plat_drv; } dbg_print("Regist S3C LED Platform Driver successfully.\n"); return 0; fail_reg_plat_drv: platform_driver_unregister(&s3c_led_driver); fail_reg_plat_dev: return ret; } static void s3c_led_exit(void) { dbg_print("%s():%d remove LED platform drvier\n", __FUNCTION__,__LINE__); platform_driver_unregister(&s3c_led_driver); dbg_print("%s():%d remove LED platform device\n", __FUNCTION__,__LINE__); platform_device_unregister(&s3c_led_device); } module_init(s3c_led_init); module_exit(s3c_led_exit); module_param(debug, int, S_IRUGO); module_param(dev_major, int, S_IRUGO); module_param(dev_minor, int, S_IRUGO); MODULE_AUTHOR(DRV_AUTHOR); MODULE_DESCRIPTION(DRV_DESC); MODULE_LICENSE("GPL"); MODULE_ALIAS("platform:S3C24XX_led");
学习驱动后的小结：
一、
static struct platform_device s3c_led_device = {
.name = "s3c_led",
.id = 1,
.dev =
{
.platform_data = &s3c_led_data,
.release = platform_led_release,
},
};
static struct platform_driver s3c_led_driver = {
.probe = s3c_led_probe,
.remove = s3c_led_remove,
.driver = {
.name = "s3c_led",
.owner = THIS_MODULE,
},
};
注意：驱动和设备的结构体成员有差别，但是用来匹配识别的name域却是相同的。只有这样才能实现互相匹配，实现驱动找设备，设备找驱动的互找。
二、
首先加载驱动时调用s3c_led_init（）函数分别注册platfrom设备和platfrom驱动。
而对于platfrom_devices设备链来说:
Platfrom_device_register -> 调用（platform_device）结构体类型的结构体s3c_led_device，结构体中定义name域和id以及设备dev信息的函数指针，其中 -> 设备数据又存放在结构体类型为（s3c_led_platform_data）的结构体变量s3c_led_data中 -> s3c_led_data成员leds函数指针指向s3c_led_info结构体类型的s3c_leds结构体数组中。nleds函数指针指向一个内核中的宏定义ARRAY_SIZE（），可以求出设备的个数。
对于platfrom_driver 驱动链来说：
Platfrom_driver_register -> 调用（platform_driver）结构体类型的结构体s3c_led_driver，结构体中有指向s3c_led_probe的probe指针和remove指针以及driver指针 -> 加载驱动链调用了s3c_led_driver结构体变量后首先便会调用s3c_led_probe函数。而probe函数的参数是platform_device结构体类型的指针。 -> 其中首先定义了一个s3c_led_platfrom_data类型的指针获取设备的信息。然后依次更改LED灯gpio口的状态以及通过判断主设备号静态或者动态的获取设备号。 -> 初始化cdev结构体，并且将fops结构体与之绑定。字符设备驱动注册
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