文章目錄

• • 1 概述
  • 2 代碼實現
  • 3 代碼分析
  • • 3.1 注意事項

1 概述

原來的框架：

要實現的框架：

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2 代碼實現

代碼結構如下：

board_A_led.c：

#include <linux/module.h>#include <linux/fs.h> #include <linux/errno.h> #include <linux/miscdevice.h> #include <linux/kernel.h> #include <linux/major.h> #include <linux/mutex.h> #include <linux/proc_fs.h> #include <linux/seq_file.h> #include <linux/stat.h> #include <linux/init.h> #include <linux/device.h> #include <linux/tty.h> #include <linux/kmod.h> #include <linux/gfp.h> #include <linux/platform_device.h>#include "led_resource.h"static void led_dev_release(struct device *dev) { }static struct resource resources[] = {{.start = GROUP_PIN(3,1),.flags = IORESOURCE_IRQ,.name = "100ask_led_pin",},{.start = GROUP_PIN(5,8),.flags = IORESOURCE_IRQ,.name = "100ask_led_pin",}, };static struct platform_device board_A_led_dev = {.name = "100ask_led",.num_resources = ARRAY_SIZE(resources),.resource = resources,.dev = {.release = led_dev_release,}, };static int __init led_dev_init(void) {int err;err = platform_device_register(&board_A_led_dev); return 0; }static void __exit led_dev_exit(void) {platform_device_unregister(&board_A_led_dev); }module_init(led_dev_init); module_exit(led_dev_exit);MODULE_LICENSE("GPL");

chip_demo_gpio.c：

#include <linux/module.h>#include <linux/fs.h> #include <linux/errno.h> #include <linux/miscdevice.h> #include <linux/kernel.h> #include <linux/major.h> #include <linux/mutex.h> #include <linux/proc_fs.h> #include <linux/seq_file.h> #include <linux/stat.h> #include <linux/init.h> #include <linux/device.h> #include <linux/tty.h> #include <linux/kmod.h> #include <linux/gfp.h> #include <linux/platform_device.h>#include "led_opr.h" #include "leddrv.h" #include "led_resource.h"static int g_ledpins[100]; static int g_ledcnt = 0;static int board_demo_led_init (int which) /* 初始化LED, which-哪個LED */ { //printk("%s %s line %d, led %d\n", __FILE__, __FUNCTION__, __LINE__, which);printk("init gpio: group %d, pin %d\n", GROUP(g_ledpins[which]), PIN(g_ledpins[which]));switch(GROUP(g_ledpins[which])){case 0:{printk("init pin of group 0 ...\n");break;}case 1:{printk("init pin of group 1 ...\n");break;}case 2:{printk("init pin of group 2 ...\n");break;}case 3:{printk("init pin of group 3 ...\n");break;}}return 0; }static int board_demo_led_ctl (int which, char status) /* 控制LED, which-哪個LED, status:1-亮,0-滅 */ {//printk("%s %s line %d, led %d, %s\n", __FILE__, __FUNCTION__, __LINE__, which, status ? "on" : "off");printk("set led %s: group %d, pin %d\n", status ? "on" : "off", GROUP(g_ledpins[which]), PIN(g_ledpins[which]));switch(GROUP(g_ledpins[which])){case 0:{printk("set pin of group 0 ...\n");break;}case 1:{printk("set pin of group 1 ...\n");break;}case 2:{printk("set pin of group 2 ...\n");break;}case 3:{printk("set pin of group 3 ...\n");break;}}return 0; }static struct led_operations board_demo_led_opr = {.init = board_demo_led_init,.ctl = board_demo_led_ctl, };struct led_operations *get_board_led_opr(void) {return &board_demo_led_opr; }static int chip_demo_gpio_probe(struct platform_device *pdev) {struct resource *res;int i = 0;while (1){res = platform_get_resource(pdev, IORESOURCE_IRQ, i++);if (!res)break;g_ledpins[g_ledcnt] = res->start;led_class_create_device(g_ledcnt);g_ledcnt++;}return 0;}static int chip_demo_gpio_remove(struct platform_device *pdev) {struct resource *res;int i = 0;while (1){res = platform_get_resource(pdev, IORESOURCE_IRQ, i);if (!res)break;led_class_destroy_device(i);i++;g_ledcnt--;}return 0; }static struct platform_driver chip_demo_gpio_driver = {.probe = chip_demo_gpio_probe,.remove = chip_demo_gpio_remove,.driver = {.name = "100ask_led",}, };static int __init chip_demo_gpio_drv_init(void) {int err;err = platform_driver_register(&chip_demo_gpio_driver); register_led_operations(&board_demo_led_opr);return 0; }static void __exit lchip_demo_gpio_drv_exit(void) {platform_driver_unregister(&chip_demo_gpio_driver); }module_init(chip_demo_gpio_drv_init); module_exit(lchip_demo_gpio_drv_exit);MODULE_LICENSE("GPL");

leddrv.c：

#include <linux/module.h>#include <linux/fs.h> #include <linux/errno.h> #include <linux/miscdevice.h> #include <linux/kernel.h> #include <linux/major.h> #include <linux/mutex.h> #include <linux/proc_fs.h> #include <linux/seq_file.h> #include <linux/stat.h> #include <linux/init.h> #include <linux/device.h> #include <linux/tty.h> #include <linux/kmod.h> #include <linux/gfp.h>#include "led_opr.h"/* 1. 確定主設備號 */ static int major = 0; static struct class *led_class; struct led_operations *p_led_opr;#define MIN(a, b) (a < b ? a : b)void led_class_create_device(int minor) {device_create(led_class, NULL, MKDEV(major, minor), NULL, "100ask_led%d", minor); /* /dev/100ask_led0,1,... */ } void led_class_destroy_device(int minor) {device_destroy(led_class, MKDEV(major, minor)); } void register_led_operations(struct led_operations *opr) {p_led_opr = opr; }EXPORT_SYMBOL(led_class_create_device); EXPORT_SYMBOL(led_class_destroy_device); EXPORT_SYMBOL(register_led_operations);/* 3. 實現對應的open/read/write等函數，填入file_operations結構體 */ static ssize_t led_drv_read (struct file *file, char __user *buf, size_t size, loff_t *offset) {printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);return 0; }/* write(fd, &val, 1); */ static ssize_t led_drv_write (struct file *file, const char __user *buf, size_t size, loff_t *offset) {int err;char status;struct inode *inode = file_inode(file);int minor = iminor(inode);printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);err = copy_from_user(&status, buf, 1);/* 根據次設備號和status控制LED */p_led_opr->ctl(minor, status);return 1; }static int led_drv_open (struct inode *node, struct file *file) {int minor = iminor(node);printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);/* 根據次設備號初始化LED */p_led_opr->init(minor);return 0; }static int led_drv_close (struct inode *node, struct file *file) {printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);return 0; }/* 2. 定義自己的file_operations結構體 */ static struct file_operations led_drv = {.owner = THIS_MODULE,.open = led_drv_open,.read = led_drv_read,.write = led_drv_write,.release = led_drv_close, };/* 4. 把file_operations結構體告訴內核：注冊驅動程序 */ /* 5. 誰來注冊驅動程序啊？得有一個入口函數：安裝驅動程序時，就會去調用這個入口函數 */ static int __init led_init(void) {int err;printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);major = register_chrdev(0, "100ask_led", &led_drv); /* /dev/led */led_class = class_create(THIS_MODULE, "100ask_led_class");err = PTR_ERR(led_class);if (IS_ERR(led_class)) {printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);unregister_chrdev(major, "led");return -1;}return 0; }/* 6. 有入口函數就應該有出口函數：卸載驅動程序時，就會去調用這個出口函數 */ static void __exit led_exit(void) {printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);class_destroy(led_class);unregister_chrdev(major, "100ask_led"); }/* 7. 其他完善：提供設備信息，自動創建設備節點 */module_init(led_init); module_exit(led_exit);MODULE_LICENSE("GPL");

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3 代碼分析

3.1 注意事項

① 如果 platform_device 中不提供 release 函數，如下圖所示不提供紅框部分的函數：

則在調用 platform_device_unregister 時會出現警告，如下圖所示：

你可以提供一個 release 函數，如果實在無事可做，把這函數寫為空。

② EXPORT_SYMBOL
a.c 編譯為 a.ko，里面定義了 func_a；如果它想讓 b.ko 使用該函數，那么 a.c 里需要導出此函數(如果 a.c, b.c 都編進內核，則無需導出)：
EXPORT_SYMBOL(led_device_create);
并且，使用時要先加載 a.ko。
如果先加載 b.ko，會有類似如下“Unknown symbol”的提示：

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