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author | Peter Korsgaard <peter.korsgaard@barco.com> | 2011-01-10 21:11:23 (GMT) |
---|---|---|
committer | Jean Delvare <khali@endymion.delvare> | 2011-01-10 21:11:23 (GMT) |
commit | 92ed1a76ca31774eb27de14b2215841367c68056 (patch) | |
tree | f9becefa5dbcdaa8cfd65100e1735044cd3910d6 /Documentation | |
parent | b18a5c80eb2e7e9c72d23f1960b09d78ddf7e5b0 (diff) | |
download | linux-fsl-qoriq-92ed1a76ca31774eb27de14b2215841367c68056.tar.xz |
i2c: Add generic I2C multiplexer using GPIO API
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>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/i2c/muxes/gpio-i2cmux | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/Documentation/i2c/muxes/gpio-i2cmux b/Documentation/i2c/muxes/gpio-i2cmux new file mode 100644 index 0000000..811cd78 --- /dev/null +++ b/Documentation/i2c/muxes/gpio-i2cmux @@ -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, + }, +}; |