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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,
},
};
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