加入次設備號，次設備號給自己的驅動程式內部使用，並了解如何撰寫驅動程式的硬體控制，與裸機程式相同，但需先利用ioremap 將 i/o 物理記憶體位置，映射到kernel虛擬地址，此後才可以使用。
first_drv.c
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <asm/arch/regs-gpio.h>
#include <asm/hardware.h>
#define DEVICE_NAME "first_drv_leds"
static struct class *leds_class;
static struct class_device *leds_class_devs[4];
volatile unsigned long *gpfcon = NULL;
volatile unsigned long *gpfdat = NULL;
static int first_drv_open(struct inode *inode, struct file *file)
{
// *gpfcon &= ~((0x3<<(4*2)) | (0x3<<(5*2)) | (0x3<<(6*2)));
// *gpfcon |= ((0x1<<(4*2)) | (0x1<<(5*2)) | (0x1<<(6*2)));
// printk("first_drv_open\n");
int minor = MINOR(inode -> i_rdev); // minor number
switch(minor)
{
// all led on
case 0:
// set GPF4,5,6 pin output
//s3c2410_gpio_cfgpin(S3C2410_GPF4, S3C2410_GPF4_OUTP);
*gpfcon &= ~(0x3<<(4*2));
*gpfcon |= (1<<(4*2));
//s3c2410_gpio_cfgpin(S3C2410_GPF5, S3C2410_GPF5_OUTP);
*gpfcon &= ~(0x3<<(5*2));
*gpfcon |= (1<<(5*2));
//s3c2410_gpio_cfgpin(S3C2410_GPF6, S3C2410_GPF6_OUTP);
*gpfcon &= ~(0x3<<(6*2));
*gpfcon |= (1<<(6*2));
break;
// led1 on
case 1:
//s3c2410_gpio_cfgpin(S3C2410_GPF4, S3C2410_GPF4_OUTP);
*gpfcon &= ~(0x3<<(4*2));
*gpfcon |= (1<<(4*2));
break;
// led2 on
case 2:
//s3c2410_gpio_cfgpin(S3C2410_GPF5, S3C2410_GPF5_OUTP);
*gpfcon &= ~(0x3<<(5*2));
*gpfcon |= (1<<(5*2));
break;
// led3 on
case 3:
//s3c2410_gpio_cfgpin(S3C2410_GPF6, S3C2410_GPF6_OUTP);
*gpfcon &= ~(0x3<<(6*2));
*gpfcon |= (1<<(6*2));
break;
}
return 0;
}
static ssize_t first_drv_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos)
{
char val;
//printk("first_drv_write\n");
int minor = MINOR(file->f_dentry->d_inode->i_rdev);
copy_from_user(&val, buf, count); // user space data transfer kernel space
switch(minor)
{
// leds
case 0:
if (val == 1)
{
// LED ON
*gpfdat &= ~((1<<4) | (1<<5) | (1<<6));
// or
//s3c2410_gpio_setpin(S3C2410_GPF4, 0);
//GPFDAT &= ~(1<<4);
//s3c2410_gpio_setpin(S3C2410_GPF5, 0);
//GPFDAT &= ~(1<<5);
//s3c2410_gpio_setpin(S3C2410_GPF6, 0);
//GPFDAT &= ~(1<<6);
}
else
{
// LED OFF
*gpfdat |= (1<<4) | (1<<5) | (1<<6);
}
break;
// led1
case 1:
if (val == 1)
{
// LED ON
*gpfdat &= ~(1<<4);
}
else
{
// LED OFF
*gpfdat |= (1<<4);
}
break;
// led2
case 2:
if (val == 1)
{
// LED ON
*gpfdat &= ~(1<<5);
}
else
{
// LED OFF
*gpfdat |= (1<<5);
}
break;
// led3
case 3:
if (val == 1)
{
// LED ON
*gpfdat &= ~(1<<6);
}
else
{
// LED OFF
*gpfdat |= (1<<6);
}
break;
}
return 0;
}
static struct file_operations first_drv_fops =
{
.owner = THIS_MODULE, /* 這是一個巨集，推向編譯模組時自動創建的__this_module變數*/
.open = first_drv_open,
.write = first_drv_write,
};
int major;
static int first_drv_init(void)
{
major = register_chrdev(0, "DEVICE_NAME", &first_drv_fops); // 向kernel註冊, major number 由系統決定，成功返回 major number
int minor = 0;
leds_class = class_create(THIS_MODULE, "leds_class");
leds_class_devs[0] = class_device_create(leds_class, NULL, MKDEV(major, 0), NULL, "leds"); // 系統自動創建 /dev/xyz
for (minor = 1; minor < 4; minor++) /* /dev/led1,2,3 */
{
leds_class_devs[minor] = class_device_create(leds_class, NULL, MKDEV(major, minor), NULL, "led%d", minor);
if (unlikely(IS_ERR(leds_class_devs[minor])))
return PTR_ERR(leds_class_devs[minor]);
}
gpfcon = (volatile unsigned long *)ioremap(0x56000050, 16);
gpfdat = gpfcon + 1;
return 0;
}
static void first_drv_exit(void)
{
unregister_chrdev(major, "DEVICE_NAME"); // 卸載
for (minor = 0; minor < 4; minor++)
{
class_device_unregister(leds_class_devs[minor]);
}
class_destroy(leds_class);
iounmap(gpfcon);
}
module_init(first_drv_init);
module_exit(first_drv_exit);
MODULE_LICENSE("GPL");
==================================================================
firstdrvtest.c
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
void print_usage(char *para)
{
printf("Usage:\n");
printf("%s <dev> <on|off>\n", para);
printf("eg. \n");
printf("%s /dev/leds on\n", para);
printf("%s /dev/leds off\n", para);
printf("%s /dev/led1 on \n", para);
printf("%s /dev/led1 off \n", para);
}
/* firstdrvtest on
* firstdrvtest off
*/
int main(int argc, char **argv)
{
int fd;
char val;
char *filename;
if(argc != 3)
{
print_usage(argv[0]);
return 0;
}
filename = argv[1];
fd = open(filename, O_RDWR);
if (fd < 0) printf("can't open!\n");
if(!strcmp(argv[2], "on"))
{
// LED ON
val = 1;
write(fd, &val, 1);
}
else if(!strcmp("off", argv[2]))
{
// LED OFF
val = 0;
write(fd, &val, 1);
}
else
return 0;
return 0;
}
=====================================================================
實驗結果:
Please press Enter to activate this console.
starting pid 772, tty '/dev/s3c2410_serial0': '/bin/sh'
#
# cd mnt/nfs/
# ls
first_drv.ko firstdrvtest
# insmod first_drv.ko
# ls -l /dev/led*
crw-rw---- 1 0 0 252, 1 Jan 1 00:04 /dev/led1
crw-rw---- 1 0 0 252, 2 Jan 1 00:04 /dev/led2
crw-rw---- 1 0 0 252, 3 Jan 1 00:04 /dev/led3
crw-rw---- 1 0 0 252, 0 Jan 1 00:04 /dev/leds
# rmmod first_drv.ko
# ls -l /dev/led*
ls: /dev/led*: No such file or directory
# insmod first_drv.ko
# ./firstdrvtest /dev/leds on <-- all led on
# ./firstdrvtest /dev/leds off <-- all led off
# ./firstdrvtest /dev/led1 on <-- led1 on
# ./firstdrvtest /dev/led1 off <-- led1 off
# ./firstdrvtest /dev/led2 on
# ./firstdrvtest /dev/led2 off
# ./firstdrvtest /dev/led3 on
# ./firstdrvtest /dev/led3 off
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