116 lines
1.9 KiB
Markdown
116 lines
1.9 KiB
Markdown
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# Linux Kernel 字符设备接口函数
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**头文件：**
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```cpp
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#include <linux/cdev.h>
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```
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## MKDEV
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**函数原型：**
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```cpp
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#define MKDEV(major,minor) (((major) << MINORBITS) | (minor))
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```
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**说明：**
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将主设备号和次设备号转换成 dev_t 类型。
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**参数：**
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major：主设备号。
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minor：次设备号。
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**返回值：**
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dev_t 类型的设备号。
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## register_chrdev_region
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**函数原型：**
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```cpp
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int register_chrdev_region(dev_t from, unsigned count, const char *name);
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```
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**说明：**
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向内核申请注册设备号。
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**参数：**
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from：dev_t 形式的设备号，可由 MKDEV 创建。
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count：申请次设备号的个数。
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name：设备名称。执行 cat /proc/devices 时会显示该名称。
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**返回值：**
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成功返回 0，否则返回错误码。
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## alloc_chrdev_region
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**函数原型：**
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```cpp
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int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count, const char *name)
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{
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struct char_device_struct *cd;
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cd = __register_chrdev_region(0, baseminor, count, name);
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if (IS_ERR(cd))
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return PTR_ERR(cd);
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*dev = MKDEV(cd->major, cd->baseminor);
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return 0;
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}
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```
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**说明：**
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动态分配主设备号。
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**参数：**
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dev：返回函数向内核申请下来的设备号。
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baseminor：起始次设备号。
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count：申请次设备号的个数。
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name：设备名称。执行 cat /proc/devices 时会显示该名称。
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**返回值：**
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成功返回 0，否则返回错误码。
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## cdev_init
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**函数原型：**
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```cpp
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void cdev_init(struct cdev *cdev, const struct file_operations *fops)
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{
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memset(cdev, 0, sizeof *cdev);
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INIT_LIST_HEAD(&cdev->list);
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kobject_init(&cdev->kobj, &ktype_cdev_default);
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cdev->ops = fops;
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}
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```
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**说明：**
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关联 cdev 和 file_operations
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**参数：**
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cdev：字符设备对象
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fops：设备操作方法
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**返回值：**
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无
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