I2C總線和SPI總線的設備樹節點解析流程

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 length2 [address2 length3] [address3 length4]..>*/

#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相當于它的子節點 */

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, 它會被轉換為platform_device, 在內核中有對應的platform_driver;

/i2c0/lm75@49節點不會被轉換為platform_device, 它被如何處理完全由父節點的platform_driver決定, 一般是被創建為一個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后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?/*?注冊I2C控制器?*/
????????????????device_register?/*?I2C控制器設備注冊?*/
????????????????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?*/
/*?添加設備成功后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?*/