Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 83 insertions, 0 deletions

diff --git a/Documentation/i2c/muxes/i2c-mux-gpio b/Documentation/i2c/muxes/i2c-mux-gpio
new file mode 100644
index 000000000..893ecdfe6
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+++ b/Documentation/i2c/muxes/i2c-mux-gpio
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+Kernel driver i2c-mux-gpio
+
+Author: Peter Korsgaard <peter.korsgaard@barco.com>
+
+Description
+-----------
+
+i2c-mux-gpio 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-mux-gpio uses the platform bus, so you need to provide a struct
+platform_device with the platform_data pointing to a struct
+i2c_mux_gpio_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/platform_data/i2c-mux-gpio.h for details.
+
+E.G. something like this for a MUX providing 4 bus segments
+controlled through 3 GPIO pins:
+
+#include <linux/platform_data/i2c-mux-gpio.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 i2c_mux_gpio_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-mux-gpio",
+	.id		= 0,
+	.dev		= {
+		.platform_data	= &myboard_i2cmux_data,
+	},
+};
+
+If you don't know the absolute GPIO pin numbers at registration time,
+you can instead provide a chip name (.chip_name) and relative GPIO pin
+numbers, and the i2c-mux-gpio driver will do the work for you,
+including deferred probing if the GPIO chip isn't immediately
+available.
+
+Device Registration
+-------------------
+
+When registering your i2c-mux-gpio device, you should pass the number
+of any GPIO pin it uses as the device ID. This guarantees that every
+instance has a different ID.
+
+Alternatively, if you don't need a stable device name, you can simply
+pass PLATFORM_DEVID_AUTO as the device ID, and the platform core will
+assign a dynamic ID to your device. If you do not know the absolute
+GPIO pin numbers at registration time, this is even the only option.