/include/linux/miscdevice.h
#ifndef _LINUX_MISCDEVICE_H
#define _LINUX_MISCDEVICE_H
#include <linux/module.h>
#include <linux/major.h>
#define PSMOUSE_MINOR 1
#define MS_BUSMOUSE_MINOR 2
#define ATIXL_BUSMOUSE_MINOR 3
/*#define AMIGAMOUSE_MINOR 4 FIXME OBSOLETE */
#define ATARIMOUSE_MINOR 5
#define SUN_MOUSE_MINOR 6
#define APOLLO_MOUSE_MINOR 7
#define PC110PAD_MINOR 9
/*#define ADB_MOUSE_MINOR 10 FIXME OBSOLETE */
#define WATCHDOG_MINOR 130 /* Watchdog timer */
#define TEMP_MINOR 131 /* Temperature Sensor */
#define RTC_MINOR 135
#define EFI_RTC_MINOR 136 /* EFI Time services */
#define SUN_OPENPROM_MINOR 139
#define DMAPI_MINOR 140 /* DMAPI */
#define NVRAM_MINOR 144
#define SGI_MMTIMER 153
#define STORE_QUEUE_MINOR 155
#define I2O_MINOR 166
#define MICROCODE_MINOR 184
#define MWAVE_MINOR 219 /* ACP/Mwave Modem */
#define MPT_MINOR 220
#define MISC_DYNAMIC_MINOR 255
#define TUN_MINOR 200
#define HPET_MINOR 228
#define KVM_MINOR 232
struct device;
struct miscdevice {
int minor;
const char *name;
const struct file_operations *fops;
struct list_head list;
struct device *parent;
struct device *this_device;
};
extern int misc_register(struct miscdevice * misc);
extern int misc_deregister(struct miscdevice *misc);
#define MODULE_ALIAS_MISCDEV(minor) \
MODULE_ALIAS("char-major-" __stringify(MISC_MAJOR) \
"-" __stringify(minor))
#endif
int misc_register(struct miscdevice * misc)
{
struct miscdevice *c;
dev_t dev;
int err = 0;
INIT_LIST_HEAD(&misc->list); //初始化 成员list.
mutex_lock(&misc_mtx); //互斥体上锁, 内核同步.
list_for_each_entry(c, &misc_list, list) { //&misc_list 为misc 这类字符设备的//
链表头, 从而用 list_for_each_entry()
可以遍历 &misc_list 中的每个 struct
miscdevice
结构体.
if (c->minor == misc->minor) { //次设备号有没有注册过?
mutex_unlock(&misc_mtx);
return -EBUSY;
}
}
if (misc->minor == MISC_DYNAMIC_MINOR) { //是否为动态分配次设备号
int i = DYNAMIC_MINORS;
while (--i >= 0)
if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
break;
if (i<0) {
mutex_unlock(&misc_mtx); //互斥体上锁, 内核同步.与mutex_lock(&misc_mtx)对应.
return -EBUSY;
}
misc->minor = i;
}
if (misc->minor < DYNAMIC_MINORS)
misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
dev = MKDEV(MISC_MAJOR, misc->minor); //主设备号10 与生成的次设备号
生成一个dev_t;
misc->this_device = device_create(misc_class, misc->parent, dev, NULL, //生成设备节点
"%s", misc->name); // /sys/class/misc/
if (IS_ERR(misc->this_device)) {
err = PTR_ERR(misc->this_device);
goto out;
}
/*
* Add it to the front, so that later devices can "override"
* earlier defaults
*/
list_add(&misc->list, &misc_list); //把申请到的misc 设备加到
&misc_list 链表头中.
out:
mutex_unlock(&misc_mtx);
return err;
}
int misc_deregister(struct miscdevice *misc)
{
int i = misc->minor;
if (list_empty(&misc->list))
return -EINVAL;
mutex_lock(&misc_mtx);
list_del(&misc->list);
device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
if (i < DYNAMIC_MINORS && i>0) {
misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
}
mutex_unlock(&misc_mtx);
return 0;
}
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