pcDuino Linux驱动开发三 -- 最简单的GPIO驱动

tjcfeng · 发表于 2014-11-30 23:12:31

本着从易到难的过程，现有程序完全基于那个最精简的驱动程序框架来实现，也就是字符设备+寄存器操作的方式，以后有时间再改为总线设备驱动。
pcDuino上有两个LED，TX和RX，就用它们来做实验了。

下面上代码，可参照《pcDuino Linux驱动开发二 -- 最简单的驱动程序框架》这个最精简的框架来看看增加的部分，无非就是多了些寄存器的操作：

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include "../A10.h"
/**********************************************************************/
#define LED_TX 15
#define LED_RX 16
#define LED_ON(Pin) (*REG_PH_DAT &= ~(0x1 << Pin))
#define LED_OFF(Pin) (*REG_PH_DAT |= (0x1 << Pin) )
#define LED_REVERSE(Pin) (*REG_PH_DAT ^= (0x1 << Pin) )
volatile static unsigned long* REG_PH_CFG1;
volatile static unsigned long* REG_PH_DAT;
int Inited = 0;
int LED_open(struct inode* n, struct file* f)
{
Inited++;
if (Inited > 1) return Inited;
REG_PH_CFG1 = (volatile unsigned long*) ioremap(PH_CFG1, 4);
REG_PH_DAT = (volatile unsigned long*) ioremap(PH_DAT, 4);
*REG_PH_CFG1 &= ~(0xF << 28);
*REG_PH_CFG1 |= (0x1 << 28);
LED_OFF(LED_TX);
LED_OFF(LED_RX);
printk("Open Finished!\n");
return 0;
}
ssize_t LED_write(struct file* f, const char __user* buf, size_t len, loff_t* l)
{
unsigned char Buf[2];
if (copy_from_user(&Buf, buf, len)) return -1;
if ((Buf[0] != LED_TX) && (Buf[0] != LED_RX)) return -1;
switch (Buf[1])
{
case 0:
LED_OFF(Buf[0]);
break;
case 1:
LED_ON(Buf[0]);
break;
case 2:
LED_REVERSE(Buf[0]);
break;
default:
return -1;
}
return len;
}
ssize_t LED_read(struct file* f, char __user* buf, size_t len, loff_t* l)
{
//int Buf;
//copy_to_user(&Buf, buf, sizeof(int));
printk("Read Finished!\n");
return 0;
}
int LED_release(struct inode* n, struct file* f)
{
Inited--;
if (Inited <= 0)
{
Inited = 0;
return 0;
}
iounmap(REG_PH_CFG1);
iounmap(REG_PH_DAT);
printk("Release Finished!\n");
return 0;
}
/**********************************************************************/
#define DEV_NAME "LED"
#define DEV_COUNT 1
static dev_t Dev_Num;
static struct cdev* pDev;
static struct class* pClass;
static struct file_operations fops =
{
.owner = THIS_MODULE,
.open = LED_open,
.write = LED_write,
.read = LED_read,
.release = LED_release,
};
static int __init LED_init(void)
{
int Result;
Result = alloc_chrdev_region(&Dev_Num, 0, DEV_COUNT, DEV_NAME);
if (Result)
{
printk("alloc_chrdev_region fail!\n");
return Result;
}
pDev = cdev_alloc();
if (pDev == NULL)
{
printk("cdev_alloc fail!\n");
unregister_chrdev_region(Dev_Num, DEV_COUNT);
return -1;
}
cdev_init(pDev, &fops);
Result = cdev_add(pDev, Dev_Num, DEV_COUNT);
if (Result)
{
printk("cdev_add fail!\n");
cdev_del(pDev);
return Result;
}
pClass = class_create(THIS_MODULE, DEV_NAME);
if (pClass == NULL)
{
printk("class_create fail!\n");
cdev_del(pDev);
unregister_chrdev_region(Dev_Num, DEV_COUNT);
return -1;
}
device_create(pClass, NULL, Dev_Num, "%s", DEV_NAME);
printk("Init Finished!\n");
return 0;
}
static void __exit LED_exit(void)
{
if (pClass)
{
device_destroy(pClass, Dev_Num);
class_destroy(pClass);
}
if (pDev)
{
cdev_del(pDev);
}
unregister_chrdev_region(Dev_Num, DEV_COUNT);
printk("Exit Finished!\n");
}
MODULE_LICENSE("GPL");
MODULE_AUTHOR("LiuYang");
module_init(LED_init);
module_exit(LED_exit);

复制代码
这里没有实现Read函数，可以略过。
make 后生成LED.ko，使用insmod LED.ko加载模块，可以在/dev文件夹中看到，或者使用cat /proc/devices也可以看到。
调用rmmod LED后，该设备驱动模块被卸载，使用dmesg | tail -10来观察各个接口的加载情况，调试用。

pcDuino Linux驱动开发三 -- 最简单的GPIO驱动

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