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i2c: Add generic I2C multiplexer using GPIO API

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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
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38
include/linux/gpio-i2cmux.h Normal file
View file

@ -0,0 +1,38 @@
/*
* gpio-i2cmux interface to platform code
*
* Peter Korsgaard <peter.korsgaard@barco.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef _LINUX_GPIO_I2CMUX_H
#define _LINUX_GPIO_I2CMUX_H
/* MUX has no specific idle mode */
#define GPIO_I2CMUX_NO_IDLE ((unsigned)-1)
/**
* struct gpio_i2cmux_platform_data - Platform-dependent data for gpio-i2cmux
* @parent: Parent I2C bus adapter number
* @base_nr: Base I2C bus number to number adapters from or zero for dynamic
* @values: Array of bitmasks of GPIO settings (low/high) for each
* position
* @n_values: Number of multiplexer positions (busses to instantiate)
* @gpios: Array of GPIO numbers used to control MUX
* @n_gpios: Number of GPIOs used to control MUX
* @idle: Bitmask to write to MUX when idle or GPIO_I2CMUX_NO_IDLE if not used
*/
struct gpio_i2cmux_platform_data {
int parent;
int base_nr;
const unsigned *values;
int n_values;
const unsigned *gpios;
int n_gpios;
unsigned idle;
};
#endif /* _LINUX_GPIO_I2CMUX_H */