[Linux] 内核中 SPI 设备驱动模型（Platform设备驱动方式）

传统 Platform设备驱动方式 中 SPI 驱动模型

#include <linux/module.h>
#include <linux/spi/spi.h>

#define DEVICE_NAME   "sensor"
#define SENSOR_SPI_BUS 0
struct spi_device *sensor_spi = NULL;

int sensor_spi_write(void)
{
// 调用平台的接口实现 spi_write
return 0;
}

int sensor_spi_read(void)
{
// 调用平台的接口实现 spi_read
return 0;
}

static const struct spi_device_id sensor_spi_id[] = {
{ DEVICE_NAME, 0 },
{ }
};

MODULE_DEVICE_TABLE(spi, sensor_spi_id);

static int  sensor_probe(struct spi_device *spi)
{
sensor_spi = spi;
return 0;
}

static int  sensor_remove(struct spi_device *spi)
{
return 0;
}

static struct spi_driver sensor_driver = {
.driver = {
.name  = DEVICE_NAME,
.owner = THIS_MODULE,
},
.probe    =  sensor_probe,
.remove   =  sensor_remove,
.id_table =  sensor_spi_id,
};

static __init int sensor_spi_init(void)
{
int status=-1;
struct spi_master *master;
struct spi_device *spi;
struct spi_board_info chip =
{
.modalias     = DEVICE_NAME,
.mode         = 0x00,
.bus_num      = 0,
.chip_select  = 0,
.max_speed_hz = 2000000,
};
spi_register_driver(&sensor_driver);
if (status<0)
{
pr_err("%s: spi_register_driver spi_driver failure. status = %d\n", __func__, status);
}
pr_err("%s: spi_register_driver spi_driver success. status = %d\n", __func__, status);
master = spi_busnum_to_master(SENSOR_SPI_BUS);
if (!master)
{
status = -ENODEV;
goto error_busnum;
}
spi = spi_new_device(master, &chip);
if (!spi)
{
status = -EBUSY;
goto error_mem;
}
return status;

error_mem:
error_busnum:
spi_unregister_driver(&sensor_driver);
return status;
}

static __exit void sensor_spi_exit(void)
{
spi_unregister_driver(&sensor_driver);
if(sensor_spi!=NULL)
spi_unregister_device(sensor_spi);
}

module_init(sensor_spi_init);
module_exit(sensor_spi_exit);
MODULE_LICENSE("GPL");

这是 3.2 版本之前的内核里spi驱动的模型。

归纳一下:

先注册 spi_board_info 结构体

匹配 spi_master,

创建 spi_device.

创建完设备之后再到 spi 总线上寻找有没有同名的spi_driver. 如果有的话就调用 spi_drive r的 probe 函数.

在 probe 函数里 register_chrdev/class_create/device_create, 创建 chrdev 然后通过 fops 里的函数来读写 spi 设备.