MISC驱动
所有的 MISC 设备驱动的主设备号都为 10，不同的设备使用不同的从设备号。 MISC 设备会自动创建 cdev，不需要像手动创建，因此采用 MISC 设备驱动可以简化字符设备驱动的编写。 需要向 Linux 注册一个 miscdevice 设备
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| struct miscdevice {
int minor;
const char *name;
const struct file_operations *fops;
struct list_head list;
struct device *parent;
struct device *this_device;
const struct attribute_group **groups;
const char *nodename;
umode_t mode;
};
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Linux 系统已经预定义了一些 MISC 设备的子设备号，这些预定义的子设备号定义在include/linux/miscdevice.h 文件中，如下所示：
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| 13 #define PSMOUSE_MINOR 1
14 #define MS_BUSMOUSE_MINOR 2
15 #define ATIXL_BUSMOUSE_MINOR 3
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17 #define ATARIMOUSE_MINOR 5
18 #define SUN_MOUSE_MINOR 6
......
52 #define MISC_DYNAMIC_MINOR 255
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注册和删除设备
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| int misc_register(struct miscdevice * misc)
int misc_deregister(struct miscdevice *misc)
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eg：
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| #include <linux/module.h>
#include <linux/kernel.h>
#include <linux/gpio.h>
#include <linux/fs.h>
#include <linux/fcntl.h>
#include <linux/errno.h>
#include <linux/of_gpio.h>
#include <linux/io.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/miscdevice.h>
#include <asm/mach/map.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#define misc_beepname "miscbeep"
#define beep_minor 144
#define BEEPON 1
#define BEEPOFF 0
struct miscbeep_dev{
dev_t devid;
struct cdev cdev;
struct class *class;
struct device *device;
struct device_node *nd;
int beep_gpio;
};
struct miscbeep_dev miscbeep;
static int misc_beep_open(struct inode *inode, struct file *filp)
{
filp -> private_data = &miscbeep;
return 0;
}
static ssize_t misc_beep_write(struct file *filp, const char __user *buf, size_t cnt,loff_t *offt )
{
int retvalue;
unsigned char databuf[1];
unsigned char state;
struct miscbeep_dev *dev = filp->private_data;
retvalue = copy_from_user(databuf, buf, cnt);
if(retvalue < 0)
{
printk("can't find user's data\r\n");
return -EFAULT;
}
state = databuf[0];
if(state == BEEPON)
{
gpio_set_value(dev->beep_gpio, 0);
}else if(state == BEEPOFF)
{
gpio_set_value(dev->beep_gpio, 1);
}
return 0;
}
static struct file_operations misc_beep_fops = {
.owner = THIS_MODULE,
.open = misc_beep_open,
.write = misc_beep_write,
};
static struct miscdevice beep_miscdev = {
.minor = beep_minor,
.name = misc_beepname,
.fops = &misc_beep_fops,
};
static int miscbeep_probe(struct platform_device *dev)
{
int ret = 0;
printk("beep driver and device have matched\r\n");
miscbeep.nd = of_find_node_by_path("/beep");
if(miscbeep.nd == NULL)
{
printk("beep node can't find\r\n");
return -EINVAL;
}
miscbeep.beep_gpio = of_get_named_gpio(miscbeep.nd, "beep-gpio", 0);
if(miscbeep.beep_gpio < 0 )
{
printk("can't get beep-gpio\r\n");
return -EINVAL;
}
ret = gpio_direction_output(miscbeep.beep_gpio, 1);
if(ret < 0)
{
printk("misc device register failed!\r\n");
return -EFAULT;
}
ret = misc_register(&beep_miscdev);
if(ret < 0)
{
printk("misc device register failed\r\n");
return -EFAULT;
}
return 0;
}
static int miscbeep_remove(struct platform_device *dev)
{
gpio_set_value(miscbeep.beep_gpio, 1);
gpio_free(miscbeep.beep_gpio);
misc_deregister(&beep_miscdev);
return 0;
}
static const struct of_device_id beep_of_match[] = {
{.compatible = "atkalpha-beep"},
{}
};
static struct platform_driver beep_driver = {
.driver = {
.name = "imx6ul-beep",
.of_match_table = beep_of_match,
},
.probe = miscbeep_probe,
.remove = miscbeep_remove,
};
static int __init miscbeep_init(void)
{
return platform_driver_register(&beep_driver);
}
static void __exit miscbeep_exit(void)
{
platform_driver_unregister(&beep_driver);
}
module_init(miscbeep_init);
module_exit(miscbeep_exit);
MODULE_LICENSE("GPL");
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