92ed1a76ca
Add an i2c mux driver providing access to i2c bus segments using a hardware MUX sitting on a master bus and controlled through gpio pins. E.G. something like: ---------- ---------- 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. Signed-off-by: Peter Korsgaard <peter.korsgaard@barco.com> Signed-off-by: Jean Delvare <khali@linux-fr.org>
65 lines
2 KiB
Text
65 lines
2 KiB
Text
Kernel driver gpio-i2cmux
|
|
|
|
Author: Peter Korsgaard <peter.korsgaard@barco.com>
|
|
|
|
Description
|
|
-----------
|
|
|
|
gpio-i2cmux 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
|
|
-----
|
|
|
|
gpio-i2cmux uses the platform bus, so you need to provide a struct
|
|
platform_device with the platform_data pointing to a struct
|
|
gpio_i2cmux_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/gpio-i2cmux.h for details.
|
|
|
|
E.G. something like this for a MUX providing 4 bus segments
|
|
controlled through 3 GPIO pins:
|
|
|
|
#include <linux/gpio-i2cmux.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 gpio_i2cmux_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 = "gpio-i2cmux",
|
|
.id = 0,
|
|
.dev = {
|
|
.platform_data = &myboard_i2cmux_data,
|
|
},
|
|
};
|