mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-17 01:34:00 +08:00
62ea22c495
This header only contains platform_data. Move it to the proper directory. Signed-off-by: Wolfram Sang <wsa@the-dreams.de> Acked-by: Peter Korsgaard <peter.korsgaard@barco.com>
84 lines
2.8 KiB
Plaintext
84 lines
2.8 KiB
Plaintext
Kernel driver i2c-mux-gpio
|
|
|
|
Author: Peter Korsgaard <peter.korsgaard@barco.com>
|
|
|
|
Description
|
|
-----------
|
|
|
|
i2c-mux-gpio is an i2c mux driver providing access to I2C bus segments
|
|
from a master I2C bus and a hardware MUX controlled through GPIO pins.
|
|
|
|
E.G.:
|
|
|
|
---------- ---------- Bus segment 1 - - - - -
|
|
| | SCL/SDA | |-------------- | |
|
|
| |------------| |
|
|
| | | | Bus segment 2 | |
|
|
| Linux | GPIO 1..N | MUX |--------------- Devices
|
|
| |------------| | | |
|
|
| | | | Bus segment M
|
|
| | | |---------------| |
|
|
---------- ---------- - - - - -
|
|
|
|
SCL/SDA of the master I2C bus is multiplexed to bus segment 1..M
|
|
according to the settings of the GPIO pins 1..N.
|
|
|
|
Usage
|
|
-----
|
|
|
|
i2c-mux-gpio uses the platform bus, so you need to provide a struct
|
|
platform_device with the platform_data pointing to a struct
|
|
i2c_mux_gpio_platform_data with the I2C adapter number of the master
|
|
bus, the number of bus segments to create and the GPIO pins used
|
|
to control it. See include/linux/platform_data/i2c-mux-gpio.h for details.
|
|
|
|
E.G. something like this for a MUX providing 4 bus segments
|
|
controlled through 3 GPIO pins:
|
|
|
|
#include <linux/platform_data/i2c-mux-gpio.h>
|
|
#include <linux/platform_device.h>
|
|
|
|
static const unsigned myboard_gpiomux_gpios[] = {
|
|
AT91_PIN_PC26, AT91_PIN_PC25, AT91_PIN_PC24
|
|
};
|
|
|
|
static const unsigned myboard_gpiomux_values[] = {
|
|
0, 1, 2, 3
|
|
};
|
|
|
|
static struct i2c_mux_gpio_platform_data myboard_i2cmux_data = {
|
|
.parent = 1,
|
|
.base_nr = 2, /* optional */
|
|
.values = myboard_gpiomux_values,
|
|
.n_values = ARRAY_SIZE(myboard_gpiomux_values),
|
|
.gpios = myboard_gpiomux_gpios,
|
|
.n_gpios = ARRAY_SIZE(myboard_gpiomux_gpios),
|
|
.idle = 4, /* optional */
|
|
};
|
|
|
|
static struct platform_device myboard_i2cmux = {
|
|
.name = "i2c-mux-gpio",
|
|
.id = 0,
|
|
.dev = {
|
|
.platform_data = &myboard_i2cmux_data,
|
|
},
|
|
};
|
|
|
|
If you don't know the absolute GPIO pin numbers at registration time,
|
|
you can instead provide a chip name (.chip_name) and relative GPIO pin
|
|
numbers, and the i2c-mux-gpio driver will do the work for you,
|
|
including deferred probing if the GPIO chip isn't immediately
|
|
available.
|
|
|
|
Device Registration
|
|
-------------------
|
|
|
|
When registering your i2c-mux-gpio device, you should pass the number
|
|
of any GPIO pin it uses as the device ID. This guarantees that every
|
|
instance has a different ID.
|
|
|
|
Alternatively, if you don't need a stable device name, you can simply
|
|
pass PLATFORM_DEVID_AUTO as the device ID, and the platform core will
|
|
assign a dynamic ID to your device. If you do not know the absolute
|
|
GPIO pin numbers at registration time, this is even the only option.
|