linux驱动I2C/SPI——misc混杂设备版【普通驱动】

本文主要是介绍linux驱动I2C/SPI——misc混杂设备版【普通驱动】，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

misc的方式写驱动相对简单，最底层的还是操作寄存器，和单片机同样的原理。代码直接贴出来，非常时候新手学习。

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/ioport.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/io.h>#define GPIO_4_BASE 0x20180000
#define SDA		(1 << 3)    /* GPIO 4_3 */
#define SCL		(1 << 4)    /* GPIO 4_4 */
#define GPIO_SPI_SCL_REG	IO_ADDRESS(GPIO_4_BASE + 0x040)
#define GPIO_SPI_SDA_REG	IO_ADDRESS(GPIO_4_BASE + 0x020)
#define GPIO_SPI_SDASCL_REG	IO_ADDRESS(GPIO_4_BASE + 0x060)#define GPIO_4_DIR 			IO_ADDRESS(GPIO_4_BASE + 0x400)#define GPIO_3_BASE 0x20170000
#define CS		(1 << 2)    /* GPIO 3_3 */
#define DC		(1 << 5)    /* GPIO 3_5 */
#define GPIO_SPI_CS_REG		IO_ADDRESS(GPIO_3_BASE + 0x020)
#define GPIO_SPI_DC_REG		IO_ADDRESS(GPIO_3_BASE + 0x080)#define GPIO_3_DIR 			IO_ADDRESS(GPIO_3_BASE + 0x400)#define HW_REG(reg)		*((volatile unsigned int *)(reg))#define SEND_COMMAND	0x01
#define SEND_DATA		0x03static void spi_clr(unsigned char whichline)
{unsigned char regvalue;if(whichline == SCL){regvalue = HW_REG(GPIO_4_DIR);regvalue |= SCL;HW_REG(GPIO_4_DIR) = regvalue;HW_REG(GPIO_SPI_SCL_REG) = 0;}else if(whichline == SDA){regvalue = HW_REG(GPIO_4_DIR);regvalue |= SDA;HW_REG(GPIO_4_DIR) = regvalue;HW_REG(GPIO_SPI_SDA_REG) = 0;}else if(whichline == (SDA|SCL)){regvalue = HW_REG(GPIO_4_DIR);regvalue |= (SCL|SDA);HW_REG(GPIO_4_DIR) = regvalue;HW_REG(GPIO_SPI_SDASCL_REG) = 0;}else if(whichline == CS){regvalue = HW_REG(GPIO_3_DIR);regvalue |= CS;HW_REG(GPIO_3_DIR) = regvalue;HW_REG(GPIO_SPI_CS_REG) = 0;}else if(whichline == DC){regvalue = HW_REG(GPIO_3_DIR);regvalue |= DC;HW_REG(GPIO_3_DIR) = regvalue;HW_REG(GPIO_SPI_DC_REG) = 0;}else{printk("Error input.\n");}
}
static void spi_set(unsigned char whichline)
{unsigned char regvalue;if(whichline == SCL){regvalue = HW_REG(GPIO_4_DIR);regvalue |= SCL;HW_REG(GPIO_4_DIR) = regvalue;HW_REG(GPIO_SPI_SCL_REG) = SCL;}else if(whichline == SDA){regvalue = HW_REG(GPIO_4_DIR);regvalue |= SDA;HW_REG(GPIO_4_DIR) = regvalue;HW_REG(GPIO_SPI_SDA_REG) = SDA;}else if(whichline == (SDA|SCL)){regvalue = HW_REG(GPIO_4_DIR);regvalue |= (SCL|SDA);HW_REG(GPIO_4_DIR) = regvalue;HW_REG(GPIO_SPI_SDASCL_REG) = (SDA|SCL);}else if(whichline == CS){regvalue = HW_REG(GPIO_3_DIR);regvalue |= CS;HW_REG(GPIO_3_DIR) = regvalue;HW_REG(GPIO_SPI_CS_REG) = 0xff;}else if(whichline == DC){regvalue = HW_REG(GPIO_3_DIR);regvalue |= DC;HW_REG(GPIO_3_DIR) = regvalue;HW_REG(GPIO_SPI_DC_REG) = 0xff;}else{printk("Error input.\n");}
}
static void spi_send_byte(unsigned char c,unsigned char dir)
{unsigned char temp,i;local_irq_disable();spi_clr(CS);if(dir == 1)spi_set(DC);//dataelsespi_clr(DC);//commandtemp = c;for(i=0; i<8; i++){if(temp&0x80)spi_set(SDA);elsespi_clr(SDA);temp = temp<<1;spi_clr(SCL);udelay(2);spi_set(SCL);udelay(2);}spi_set(SCL);spi_set(CS);
}
int gpiospi_open(struct inode * inode, struct file * file)
{return 0;
}
int gpiospi_close(struct inode * inode, struct file * file)
{return 0;
}
static long gpiospi_ioctl(struct file* file, unsigned int cmd, unsigned long arg)
{switch(cmd){case SEND_COMMAND:spi_send_byte((unsigned char)arg,0);break;case SEND_DATA:spi_send_byte((unsigned char)arg,1);break;default :return -1;}	return 0;
}static struct file_operations gpiospi_fops =
{.owner      = THIS_MODULE,.unlocked_ioctl = gpiospi_ioctl,.open       = gpiospi_open,.release    = gpiospi_close,
};
static struct miscdevice gpiospi_dev =
{MISC_DYNAMIC_MINOR,"gpio_spi",&gpiospi_fops,
};static int __init gpio_spi_init(void)
{int ret;ret = misc_register(&gpiospi_dev);if(ret != 0){printk("could not register gpio_spi device\n");return -1;}printk("load gpio_spi.ko ok!\n");return ret;
}
static void __exit gpio_spi_exit(void)
{misc_deregister(&gpiospi_dev);printk("I'll be leaving, bye!\n");
}
module_init(gpio_spi_init);
module_exit(gpio_spi_exit);
MODULE_LICENSE("GPL");

非常简单的结构，连probe都没有。最核心的是misc_register和misc_deregister，基本就是填充结构体

驱动的open和write方法内没有内容，所有功能放在了ioctl内

另外一种驱动方法：嵌入了系统的I2c总线，稍微复杂一点，因为使用了平台驱动，调用了系统的框架，多了probe等方法，这样的好处是方便移植驱动。I2C和SPi原理类似，可以相互参考。