linux的驱动开发—

linux的驱动开发——设备号

1.设备号的获取

$\qquad$ 设备号的获取方法：自动分配；指定设备号注册

2.自动分配函数

$\qquad$ 函数：int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count, const char *name)
$\qquad$ 功能：分配设备号
$\qquad$ 参数：第一个参数：dev_t类型定义的变量，取地址传入；第二个参数：次设备号，次设备号自己指定；第三个参数：设备个数；第四个参数：名字
$\qquad$ 返回值：成功返回0；失败返回负数错误码

int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count, const char *name)
{struct char_device_struct *cd;cd = __register_chrdev_region(0, baseminor, count, name);if (IS_ERR(cd))return PTR_ERR(cd);*dev = MKDEV(cd->major, cd->baseminor);return 0;
}

3.指定设备号注册

$\qquad$ 函数：int register_chrdev_region(dev_t from, unsigned count, const char *name)
$\qquad$ 功能：指定设备号注册
$\qquad$ 参数：第一个参数：设备号（MKDEV(major,minor)）；第二个参数：设备个数；第三个参数：名字
$\qquad$ 返回值：成功返回0；失败返回负数错误码

int register_chrdev_region(dev_t from, unsigned count, const char *name)
{struct char_device_struct *cd;dev_t to = from + count;dev_t n, next;for (n = from; n < to; n = next) {next = MKDEV(MAJOR(n)+1, 0);if (next > to)next = to;cd = __register_chrdev_region(MAJOR(n), MINOR(n),next - n, name);if (IS_ERR(cd))goto fail;}return 0;
fail:to = n;for (n = from; n < to; n = next) {next = MKDEV(MAJOR(n)+1, 0);kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));}return PTR_ERR(cd);
}

4.注销设备号

$\qquad$ 函数：void unregister_chrdev_region(dev_t from, unsigned count)
$\qquad$ 功能：注销设备号
$\qquad$ 参数：第一个参数：设备号；第二个参数：设备个数
$\qquad$ 返回值：void

void unregister_chrdev_region(dev_t from, unsigned count)
{dev_t to = from + count;dev_t n, next;for (n = from; n < to; n = next) {next = MKDEV(MAJOR(n)+1, 0);if (next > to)next = to;kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));}
}