bus-drivers-i2c-spi

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🇺🇸

Original

English

🇨🇳

Translation

Chinese

Bus Drivers (I2C and SPI)

总线驱动（I2C和SPI）

Purpose

用途

Guide agents through Linux I2C and SPI client drivers: bus registration,

i2c_transfer

spi_sync

, regmap abstraction, DT

compatible

on bus children, and probe patterns — complementing platform MMIO drivers in

skills/kernel/device-drivers

指导Agent完成Linux I2C和SPI客户端驱动开发：总线注册、

i2c_transfer

spi_sync

、regmap抽象、总线子设备的DT

compatible

属性以及探测模式——作为

skills/kernel/device-drivers

中平台MMIO驱动的补充。

When to Use

使用场景

Sensor or PMIC on I2C/SPI bus
Converting bare-metal SPI register reads to kernel driver
Using
```
regmap
```
for multi-byte register access
Debugging
```
-EREMOTEIO
```
or missing ACK

I2C/SPI总线上的传感器或PMIC
将裸机SPI寄存器读取转换为内核驱动
使用
```
regmap
```
进行多字节寄存器访问
调试
```
-EREMOTEIO
```
错误或缺失ACK响应

Workflow

工作流程

1. I2C client driver

1. I2C客户端驱动

#include <linux/i2c.h>
#include <linux/mod_devicetable.h>

static int my_probe(struct i2c_client *client)
{
    struct regmap *map;

    map = devm_regmap_init_i2c(client, &my_regmap_config);
    if (IS_ERR(map))
        return PTR_ERR(map);

    dev_info(&client->dev, "probed at 0x%02x\n", client->addr);
    return 0;
}

static const struct of_device_id my_of_id[] = {
    { .compatible = "vendor,sensor" },
    { }
};
MODULE_DEVICE_TABLE(of, my_of_id);

static const struct i2c_device_id my_id[] = {
    { "mysensor", 0 },
    { }
};
MODULE_DEVICE_TABLE(i2c, my_id);

static struct i2c_driver my_driver = {
    .probe    = my_probe,
    .remove   = my_remove,
    .driver   = { .name = "mysensor", .of_match_table = my_of_id },
    .id_table = my_id,
};
module_i2c_driver(my_driver);

DT child:

dts

i2c1 {
    sensor@48 {
        compatible = "vendor,sensor";
        reg = <0x48>;
    };
};

#include <linux/i2c.h>
#include <linux/mod_devicetable.h>

static int my_probe(struct i2c_client *client)
{
    struct regmap *map;

    map = devm_regmap_init_i2c(client, &my_regmap_config);
    if (IS_ERR(map))
        return PTR_ERR(map);

    dev_info(&client->dev, "probed at 0x%02x\n", client->addr);
    return 0;
}

static const struct of_device_id my_of_id[] = {
    { .compatible = "vendor,sensor" },
    { }
};
MODULE_DEVICE_TABLE(of, my_of_id);

static const struct i2c_device_id my_id[] = {
    { "mysensor", 0 },
    { }
};
MODULE_DEVICE_TABLE(i2c, my_id);

static struct i2c_driver my_driver = {
    .probe    = my_probe,
    .remove   = my_remove,
    .driver   = { .name = "mysensor", .of_match_table = my_of_id },
    .id_table = my_id,
};
module_i2c_driver(my_driver);

DT子节点:

dts

i2c1 {
    sensor@48 {
        compatible = "vendor,sensor";
        reg = <0x48>;
    };
};

2. Raw I2C transfer

2. 原生I2C传输

u8 reg = 0x0F, val;
struct i2c_msg msgs[] = {
    { .addr = client->addr, .flags = 0,       .len = 1, .buf = &reg },
    { .addr = client->addr, .flags = I2C_M_RD, .len = 1, .buf = &val },
};
ret = i2c_transfer(client->adapter, msgs, 2);

u8 reg = 0x0F, val;
struct i2c_msg msgs[] = {
    { .addr = client->addr, .flags = 0,       .len = 1, .buf = &reg },
    { .addr = client->addr, .flags = I2C_M_RD, .len = 1, .buf = &val },
};
ret = i2c_transfer(client->adapter, msgs, 2);

3. SPI driver

3. SPI驱动

static int spi_probe(struct spi_device *spi)
{
    spi->mode = SPI_MODE_0;
    spi->bits_per_word = 8;
    spi_setup(spi);

    struct spi_transfer t = {
        .tx_buf = tx,
        .rx_buf = rx,
        .len    = len,
    };
    struct spi_message m;
    spi_message_init(&m);
    spi_message_add_tail(&t, &m);
    return spi_sync(spi, &m);
}

static struct spi_driver spi_drv = {
    .probe  = spi_probe,
    .driver = { .name = "my-spi", .of_match_table = my_of_match },
};
module_spi_driver(spi_drv);

static int spi_probe(struct spi_device *spi)
{
    spi->mode = SPI_MODE_0;
    spi->bits_per_word = 8;
    spi_setup(spi);

    struct spi_transfer t = {
        .tx_buf = tx,
        .rx_buf = rx,
        .len    = len,
    };
    struct spi_message m;
    spi_message_init(&m);
    spi_message_add_tail(&t, &m);
    return spi_sync(spi, &m);
}

static struct spi_driver spi_drv = {
    .probe  = spi_probe,
    .driver = { .name = "my-spi", .of_match_table = my_of_match },
};
module_spi_driver(spi_drv);

4. regmap (preferred for register maps)

4. regmap（寄存器映射的首选方案）

static const struct regmap_config my_regmap_config = {
    .reg_bits   = 8,
    .val_bits   = 8,
    .max_register = 0x7F,
};

regmap_read(map, REG_STATUS, &val);
regmap_write(map, REG_CTRL, CTRL_ENABLE);
regmap_update_bits(map, REG_CTRL, MASK, ENABLE);

static const struct regmap_config my_regmap_config = {
    .reg_bits   = 8,
    .val_bits   = 8,
    .max_register = 0x7F,
};

regmap_read(map, REG_STATUS, &val);
regmap_write(map, REG_CTRL, CTRL_ENABLE);
regmap_update_bits(map, REG_CTRL, MASK, ENABLE);

5. Debug

5. 调试

bash

i2cdetect -y 1
i2cdump -y 1 0x48
cat /sys/bus/i2c/devices/i2c-1/1-0048/name