Device Tree Node parsing process of I2C bus and SPI bus
I. the parsing process of I2C nodes in the device tree
/ * i2c controller node * /
I2c0: i2c@2180000 {
Compatible = "fsl,vf610-i2c"
/ * reg = * /
# address-cells =; / * address a 32-bit representation * /
# size-cells =; / * length bit empty * /
Reg =
Interrupts =; / * GIC_SPI SPI:shared processor interrupts interrupt number 32 ~ 32mm 224 88 interrupt IRQ_TYPE_LEVEL_HIGH trigger method * /
Clock-names = "i2c"
Clocks =; / * clock used * /
Status = "disabled"
}
Reg = resolve:
I2C address 0x2180000 physical address, mapping length 0x10000, to use this physical address must be mapped to a virtual address in the driver.
/ * i2c device node * /
& i2c0 {/ * reference i2c controller 0 is equivalent to its child node * /
Status = "okay"
Lm75@49 {
Compatible = "ti,lm75"
Reg =
}
Lm75@4a {
Compatible = "ti,lm75"
Reg =
}
}
The / i2c0 node generally represents the i2C controller, which is converted to platform_device and has a corresponding platform_driver in the kernel
The / i2c0/lm75@49 node is not converted to platform_device, but how it is handled is entirely determined by the platform_driver of the parent node, which is generally created as an i2c_client.
Matching process of device tree:
Platform_match:
1. Match driver.of_match_table:of_driver_match_device / / device tree parsing
2 、 match driver.acpi_match_table
3 、 match platform_driver.id_table
4. Name and driver.name of match devices
The success of any of the above four matches is considered to be a match ok.
Code flow:
Static const struct of_device_id i2c_imx_dt_ids [] = {{.trees = "fsl,imx1-i2c", .data = & imx1_i2c_hwdata,}, {.trees = "fsl,imx21-i2c", .data = & imx21_i2c_hwdata,}, {.trees = "fsl,vf610-i2c", / * corresponding device tree compatible * / .data = & vf610_i2c_hwdata,}, {/ * sentinel * /}} Static struct platform_driver i2c_imx_driver = {. Probe = i2croomimxremove.remove.driver = {. Name = DRIVER_NAME,.pm = I2CroomIMXroomPMPMPMPMPMCOPSMagne.ofingmatchdistributable = i2c_imx_dt_ids,}, .id _ table = imx_i2c_devtype,} / * after converting the device tree to platform_device, the i2c_imx_probe function is called * / i2c_imx_probe i2c_add_numbered_adapter / * add I2C controller * / _ _ i2c_add_numbered_adapter i2c_register_adapter / * register I2C controller * / device_register / * I2C controller device registration * / of _ i2c_register_devices / * find the slave device under the device tree controller * / of_i2c_register_device i2c_new_device client- > dev.bus = & i2c_bus_type Device_register / * add device I2C looks for static tables from device * / i2c_scan_static_board_info / *. Some I2C devices are written in code, not in the form of device tree * / i2c_new_device client- > dev.bus = & i2c_bus_type Device_register / * add device I2C slave device * / / * after successfully adding a device, the I2C device at several points of lm75@49 will match the driver through i2c_bus_type.i2c_device_match. * / static const struct of_device_id lm75_of_match [] = {{.compatible = "ti,tmp75", .data = (void *) tmp75},. } static struct i2c_driver lm75_driver = {.class= I2C classrooms HWMON drawing .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,}
The lm75_probe function will be called.
2. SPI device tree node processing flow
Xx_spi_probe spi_bitbang_start spi_register_master- > spi_register_master of_register_spi_devices of_register_spi_device spi_add_device / * and i2c_new_device processing flow are the same as matching device drivers * /
