I2C总线和SPI总线的设备树节点解析流程
一、设备树中I2C节点的解析流程
/* i2c 控制器节点 */
i2c0: i2c@2180000 {
compatible = "fsl,vf610-i2c";
/*reg =
#address-cells = <1>; /* address一个32位表示*/
#size-cells = <0>; /* length位空*/
reg = <0x0 0x2180000 0x0 0x10000>;
interrupts =
clock-names = "i2c";
clocks = <&platform_clk 1>; /*使用的时钟*/
status = "disabled";
};
reg = <0x0 0x2180000 0x0 0x10000>解析：
I2C地址0x2180000物理地址，映射长度0x10000，要使用这个物理地址先要在驱动中将其映射成虚拟地址。
/* i2c设备节点 */
&i2c0 {/* 引用i2c控制器0相当于它的子节点 */
status = "okay";
lm75@49 {
compatible = "ti,lm75";
reg = <0x49>;
};
lm75@4a {
compatible = "ti,lm75";
reg = <0x4a>;
};
};
/i2c0节点一般表示i2c控制器, 它会被转换为platform_device, 在内核中有对应的platform_driver;
/i2c0/lm75@49节点不会被转换为platform_device, 它被如何处理完全由父节点的platform_driver决定, 一般是被创建为一个i2c_client。
设备树的匹配流程：
platform_match:
1、match driver.of_match_table:of_driver_match_device //设备树解析
2、match driver.acpi_match_table
3、match platform_driver.id_table
4、match 设备的name和driver.name
上面四个任意匹配成功就算匹配ok。
代码流程：
static const struct of_device_id i2c_imx_dt_ids[] = {{ .compatible = "fsl,imx1-i2c", .data = &imx1_i2c_hwdata, },{ .compatible = "fsl,imx21-i2c", .data = &imx21_i2c_hwdata, },{ .compatible = "fsl,vf610-i2c",/* 对应设备树compatible */ .data = &vf610_i2c_hwdata, },{ /* sentinel */ }};static struct platform_driver i2c_imx_driver = {.probe = i2c_imx_probe,.remove = i2c_imx_remove,.driver = {.name = DRIVER_NAME,.pm = I2C_IMX_PM_OPS,.of_match_table = i2c_imx_dt_ids,},.id_table = imx_i2c_devtype,};/* 将设备树转换成platform_device后i2c_imx_probe函数被调用 */i2c_imx_probe i2c_add_numbered_adapter /* 添加I2C控制器 */ __i2c_add_numbered_adapter i2c_register_adapter /* 注册I2C控制器 */ device_register /* I2C控制器设备注册 */ of_i2c_register_devices /* 查找设备树控制器下面的从设备 */ of_i2c_register_device i2c_new_device client->dev.bus = &i2c_bus_type; device_register /* 添加设备I2C从设备 */ i2c_scan_static_board_info /* 查找静态表，有些I2C设备是在代码中写死的，不是通过设备树的形式 */ i2c_new_device client->dev.bus = &i2c_bus_type; device_register /* 添加设备I2C从设备 *//* 添加设备成功后lm75@49几点的I2C设备将通过i2c_bus_type.i2c_device_match匹配驱动程序。*/static const struct of_device_id lm75_of_match[] = {{.compatible = "ti,tmp75",.data = (void *)tmp75},。。。。}static struct i2c_driver lm75_driver = {.class= I2C_CLASS_HWMON,.driver = {.name= "lm75",.of_match_table = of_match_ptr(lm75_of_match),.pm= LM75_DEV_PM_OPS,},.probe= lm75_probe,.id_table= lm75_ids,.detect= lm75_detect,.address_list= normal_i2c,};lm75_probe函数将被调用。
二、SPI设备树节点处理流程
xx_spi_probe spi_bitbang_start spi_register_master->spi_register_master of_register_spi_devices of_register_spi_device spi_add_device /* 和i2c_new_device处理流程就一样了匹配设备驱动 */
