一、設備樹中I2C節點的解析流程
/* i2c 控制器節點 */
i2c0: i2c@2180000 {
compatible = "fsl,vf610-i2c";
/*reg = <address1 length1 [address2 length2] [address3 length3]..>*/
#address-cells = <1>; /* address一個32位表示*/
#size-cells = <0>; /* length位空*/
reg = <0x0 0x2180000 0x0 0x10000>;
interrupts = <GIC_SPI 88 IRQ_TYPE_LEVEL_HIGH>;/*GIC_SPI SPI：shared processor interrupts 中斷號 32 ～32+224 88號中斷 IRQ_TYPE_LEVEL_HIGH觸發方式 */
clock-names = "i2c";
clocks = <&platform_clk 1>; /*使用的時鐘*/
status = "disabled";
};
reg = <0x0 0x2180000 0x0 0x10000>解析：
I2C地址0x2180000物理地址，映射長度0x10000，要使用這個物理地址先要在驅動中將其映射成虛擬地址。
/* i2c設備節點 */
&i2c0 {/* 引用i2c控制器0相當於它的子節點 */
status = "okay";
lm75@49 {
compatible = "ti,lm75";
reg = <0x49>;
};
lm75@4a {
compatible = "ti,lm75";
reg = <0x4a>;
};
};
/i2c0節點一般表示i2c控制器, 它會被轉換爲platform_device, 在內核中有對應的platform_driver;
/i2c0/lm75@49節點不會被轉換爲platform_device, 它被如何處理完全由父節點的platform_driver決定, 一般是被創建爲一個i2c_client。
設備樹的匹配流程：
platform_match:
1、match driver.of_match_table:of_driver_match_device //設備樹解析
2、match driver.acpi_match_table
3、match platform_driver.id_table
4、match 設備的name和driver.name
上面四個任意匹配成功就算匹配ok。
代碼流程：
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",/* 對應設備樹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,
};
/* 將設備樹轉換成platform_device後i2c_imx_probe函數被調用 */
i2c_imx_probe
i2c_add_numbered_adapter /* 添加I2C控制器 */
__i2c_add_numbered_adapter
i2c_register_adapter /* 註冊I2C控制器 */
device_register /* I2C控制器設備註冊 */
of_i2c_register_devices /* 查找設備樹控制器下面的從設備 */
of_i2c_register_device
i2c_new_device
client->dev.bus = &i2c_bus_type;
device_register /* 添加設備I2C從設備 */
i2c_scan_static_board_info /* 查找靜態表，有些I2C設備是在代碼中寫死的，不是通過設備樹的形式 */
i2c_new_device
client->dev.bus = &i2c_bus_type;
device_register /* 添加設備I2C從設備 */
/* 添加設備成功後lm75@49幾點的I2C設備將通過i2c_bus_type.i2c_device_match匹配驅動程序。*/
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函數將被調用。
二、SPI設備樹節點處理流程
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處理流程就一樣了匹配設備驅動 */