lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

i2c: Add generic I2C multiplexer using GPIO API

Browse Source 
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>
This commit is contained in:
Peter Korsgaard
2011-01-10 22:11:23 +01:00
committed by Jean Delvare
parent b18a5c80eb
commit 92ed1a76ca
6 changed files with 308 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

65
Documentation/i2c/muxes/gpio-i2cmux Normal file
View File

@@ -0,0 +1,65 @@
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,
},
};