summaryrefslogtreecommitdiff
path: root/Documentation/i2c/muxes/i2c-mux-gpio
diff options
context:
space:
mode:
authorH. Peter Anvin <hpa@zytor.com>2012-05-30 12:11:26 -0700
committerH. Peter Anvin <hpa@zytor.com>2012-05-30 12:11:32 -0700
commitbbd771474ec44b516107685d77e1c80bbe09f141 (patch)
tree0cb15781539a68f27b4ea6c89f827282630cbce6 /Documentation/i2c/muxes/i2c-mux-gpio
parent403e1c5b7495d7b80fae9fc4d0a7a6f5abdc3307 (diff)
parent319b6ffc6df892e4ccffff823cc5521a4a5d2dca (diff)
Merge branch 'x86/trampoline' into x86/urgent
x86/trampoline contains an urgent commit which is necessarily on a newer baseline. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'Documentation/i2c/muxes/i2c-mux-gpio')
-rw-r--r--Documentation/i2c/muxes/i2c-mux-gpio65
1 files changed, 65 insertions, 0 deletions
diff --git a/Documentation/i2c/muxes/i2c-mux-gpio b/Documentation/i2c/muxes/i2c-mux-gpio
new file mode 100644
index 000000000000..bd9b2299b739
--- /dev/null
+++ b/Documentation/i2c/muxes/i2c-mux-gpio
@@ -0,0 +1,65 @@
+Kernel driver i2c-gpio-mux
+
+Author: Peter Korsgaard <peter.korsgaard@barco.com>
+
+Description
+-----------
+
+i2c-gpio-mux 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
+-----
+
+i2c-gpio-mux 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/i2c-gpio-mux.h for details.
+
+E.G. something like this for a MUX providing 4 bus segments
+controlled through 3 GPIO pins:
+
+#include <linux/i2c-gpio-mux.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 = "i2c-gpio-mux",
+ .id = 0,
+ .dev = {
+ .platform_data = &myboard_i2cmux_data,
+ },
+};