forked from luck/tmp_suning_uos_patched
Documentation: gpio: Move GPIO mapping documentation to driver-api
Move gpio/board.txt to driver-api/gpio/board.rst and make sure it builds cleanly as ReST. Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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@ -1,3 +1,4 @@
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=============
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GPIO Mappings
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=============
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@ -23,7 +24,7 @@ device tree bindings for your controller.
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GPIOs mappings are defined in the consumer device's node, in a property named
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<function>-gpios, where <function> is the function the driver will request
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through gpiod_get(). For example:
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through gpiod_get(). For example::
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foo_device {
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compatible = "acme,foo";
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@ -40,7 +41,7 @@ it but are only supported for compatibility reasons and should not be used for
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newer bindings since it has been deprecated.
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This property will make GPIOs 15, 16 and 17 available to the driver under the
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"led" function, and GPIO 1 as the "power" GPIO:
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"led" function, and GPIO 1 as the "power" GPIO::
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struct gpio_desc *red, *green, *blue, *power;
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@ -60,13 +61,13 @@ looked up by the gpiod functions internally) used in the device tree. With above
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Internally, the GPIO subsystem prefixes the GPIO suffix ("gpios" or "gpio")
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with the string passed in con_id to get the resulting string
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(snprintf(... "%s-%s", con_id, gpio_suffixes[]).
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(``snprintf(... "%s-%s", con_id, gpio_suffixes[]``).
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ACPI
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----
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ACPI also supports function names for GPIOs in a similar fashion to DT.
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The above DT example can be converted to an equivalent ACPI description
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with the help of _DSD (Device Specific Data), introduced in ACPI 5.1:
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with the help of _DSD (Device Specific Data), introduced in ACPI 5.1::
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Device (FOO) {
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Name (_CRS, ResourceTemplate () {
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@ -105,12 +106,12 @@ Documentation/acpi/gpio-properties.txt.
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Platform Data
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-------------
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Finally, GPIOs can be bound to devices and functions using platform data. Board
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files that desire to do so need to include the following header:
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files that desire to do so need to include the following header::
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#include <linux/gpio/machine.h>
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GPIOs are mapped by the means of tables of lookups, containing instances of the
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gpiod_lookup structure. Two macros are defined to help declaring such mappings:
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gpiod_lookup structure. Two macros are defined to help declaring such mappings::
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GPIO_LOOKUP(chip_label, chip_hwnum, con_id, flags)
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GPIO_LOOKUP_IDX(chip_label, chip_hwnum, con_id, idx, flags)
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@ -141,22 +142,24 @@ end. The 'dev_id' field of the table is the identifier of the device that will
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make use of these GPIOs. It can be NULL, in which case it will be matched for
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calls to gpiod_get() with a NULL device.
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struct gpiod_lookup_table gpios_table = {
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.dev_id = "foo.0",
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.table = {
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GPIO_LOOKUP_IDX("gpio.0", 15, "led", 0, GPIO_ACTIVE_HIGH),
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GPIO_LOOKUP_IDX("gpio.0", 16, "led", 1, GPIO_ACTIVE_HIGH),
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GPIO_LOOKUP_IDX("gpio.0", 17, "led", 2, GPIO_ACTIVE_HIGH),
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GPIO_LOOKUP("gpio.0", 1, "power", GPIO_ACTIVE_LOW),
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{ },
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},
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};
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.. code-block:: c
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And the table can be added by the board code as follows:
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struct gpiod_lookup_table gpios_table = {
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.dev_id = "foo.0",
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.table = {
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GPIO_LOOKUP_IDX("gpio.0", 15, "led", 0, GPIO_ACTIVE_HIGH),
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GPIO_LOOKUP_IDX("gpio.0", 16, "led", 1, GPIO_ACTIVE_HIGH),
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GPIO_LOOKUP_IDX("gpio.0", 17, "led", 2, GPIO_ACTIVE_HIGH),
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GPIO_LOOKUP("gpio.0", 1, "power", GPIO_ACTIVE_LOW),
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{ },
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},
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};
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And the table can be added by the board code as follows::
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gpiod_add_lookup_table(&gpios_table);
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The driver controlling "foo.0" will then be able to obtain its GPIOs as follows:
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The driver controlling "foo.0" will then be able to obtain its GPIOs as follows::
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struct gpio_desc *red, *green, *blue, *power;
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@ -10,6 +10,7 @@ Contents:
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intro
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driver
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consumer
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board
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legacy
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Core
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@ -3,7 +3,5 @@
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drivers-on-gpio.txt:
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- Drivers in other subsystems that can use GPIO to provide more
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complex functionality.
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board.txt
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- How to assign GPIOs to a consumer device and a function
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sysfs.txt
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- Information about the GPIO sysfs interface
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