概述

今天看了《韦东山升级版全系列嵌入式视频之总线设备驱动模型》这一节的视频，看完之后感觉有一种似懂非懂的感觉，因此我对改节视频对应源码进行分析，结果如下：

函数关系图

模型分析

该模型分三层：

一、驱动层

二、设备层

三、资源层

数据流向大致为资源层->设备层->驱动层

资源层->设备层

要用到的引脚、设备数量等定义在资源层的resource数组内：

struct resource {

resource_size_t start;

resource_size_t end;

const char *name;

unsigned long flags;

struct resource *parent, *sibling, *child;

};

例：

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",

},

};

在设备层chip_demo_gpio.c中通过platform_get_resource()函数将resource中的数据传入设备层，并在.probe = chip_demo_gpio_probe函数中创建device,在.remove = chip_demo_gpio_remove函数中卸载device：

static struct platform_driver chip_demo_gpio_driver = {

.probe = chip_demo_gpio_probe,

.remove = chip_demo_gpio_remove,

.driver = {

.name = "100ask_led",

},

};

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;

}

设备层->驱动层

创建device的函数定义在驱动层leddrv.c:led_class_create_device()；led_class_destroy_device()定义在驱动层leddrv.c:

static struct class *led_class;

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));

}

设备层在board_demo_led_opr结构体中对硬件进行设置，并在chip_demo_gpio_drv_init()中使用register_led_operration(&board_demo_led_opr)函数将设备层中结构体led_operations board_demo_led_opr的内容传入驱动层。

led_operations board_demo_led_opr结构体的内容：

/* 在例程中没有对硬件进行操作，只写了一个框架 */

static struct led_operations board_demo_led_opr = {

.init = board_demo_led_init,//在此函数中使能时钟、设置引脚工作模式、设置输入输出模式

.ctl = board_demo_led_ctl,//在此函数中设置引脚电平

};

static int board_demo_led_init (int which) /* 初始化LED, which-哪个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-哪个LED, status:1-亮,0-灭 */

{

//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;

}

chip_demo_gpio_drv_init()函数：

static int __init chip_demo_gpio_drv_init(void)

{

int err;

err = platform_driver_register(&chip_demo_gpio_driver);

/* 此函数定义在驱动层leddrv.c,在此处使用将board_demo_led_opr中的内容传入驱动层的p_led_opr */

register_led_operations(&board_demo_led_opr);

return 0;

}

设备层leddrv.c中register_led_operration()的定义

struct led_operations *p_led_opr;

void register_led_operations(struct led_operations *opr)

{

p_led_opr = opr;

}

然后通过p_led_opr ->init()和p_led_opr ->ctl()在open和write函数中操作硬件

/* 2. 定义自己的file_operations结构体 */

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,

};

/* 3. 实现对应的open/read/write等函数，填入file_operations结构体 */

/* 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);

/* 根据次设备号和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__);

/* 根据次设备号初始化LED */

p_led_opr->init(minor);

return 0;

}

总结

总结的比较乱，但是目前我也只理解到这一步了，如果以后有了新的思路就再改吧，谢谢观看。