Commit 6960341a authored by Jonathan Neuschäfer's avatar Jonathan Neuschäfer Committed by Linus Walleij

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: default avatarJonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent 4e0edc4b
=============
GPIO Mappings
=============
......@@ -23,7 +24,7 @@ device tree bindings for your controller.
GPIOs mappings are defined in the consumer device's node, in a property named
<function>-gpios, where <function> is the function the driver will request
through gpiod_get(). For example:
through gpiod_get(). For example::
foo_device {
compatible = "acme,foo";
......@@ -40,7 +41,7 @@ it but are only supported for compatibility reasons and should not be used for
newer bindings since it has been deprecated.
This property will make GPIOs 15, 16 and 17 available to the driver under the
"led" function, and GPIO 1 as the "power" GPIO:
"led" function, and GPIO 1 as the "power" GPIO::
struct gpio_desc *red, *green, *blue, *power;
......@@ -60,13 +61,13 @@ looked up by the gpiod functions internally) used in the device tree. With above
Internally, the GPIO subsystem prefixes the GPIO suffix ("gpios" or "gpio")
with the string passed in con_id to get the resulting string
(snprintf(... "%s-%s", con_id, gpio_suffixes[]).
(``snprintf(... "%s-%s", con_id, gpio_suffixes[]``).
ACPI
----
ACPI also supports function names for GPIOs in a similar fashion to DT.
The above DT example can be converted to an equivalent ACPI description
with the help of _DSD (Device Specific Data), introduced in ACPI 5.1:
with the help of _DSD (Device Specific Data), introduced in ACPI 5.1::
Device (FOO) {
Name (_CRS, ResourceTemplate () {
......@@ -105,12 +106,12 @@ Documentation/acpi/gpio-properties.txt.
Platform Data
-------------
Finally, GPIOs can be bound to devices and functions using platform data. Board
files that desire to do so need to include the following header:
files that desire to do so need to include the following header::
#include <linux/gpio/machine.h>
GPIOs are mapped by the means of tables of lookups, containing instances of the
gpiod_lookup structure. Two macros are defined to help declaring such mappings:
gpiod_lookup structure. Two macros are defined to help declaring such mappings::
GPIO_LOOKUP(chip_label, chip_hwnum, con_id, flags)
GPIO_LOOKUP_IDX(chip_label, chip_hwnum, con_id, idx, flags)
......@@ -141,22 +142,24 @@ end. The 'dev_id' field of the table is the identifier of the device that will
make use of these GPIOs. It can be NULL, in which case it will be matched for
calls to gpiod_get() with a NULL device.
struct gpiod_lookup_table gpios_table = {
.dev_id = "foo.0",
.table = {
GPIO_LOOKUP_IDX("gpio.0", 15, "led", 0, GPIO_ACTIVE_HIGH),
GPIO_LOOKUP_IDX("gpio.0", 16, "led", 1, GPIO_ACTIVE_HIGH),
GPIO_LOOKUP_IDX("gpio.0", 17, "led", 2, GPIO_ACTIVE_HIGH),
GPIO_LOOKUP("gpio.0", 1, "power", GPIO_ACTIVE_LOW),
{ },
},
};
.. code-block:: c
struct gpiod_lookup_table gpios_table = {
.dev_id = "foo.0",
.table = {
GPIO_LOOKUP_IDX("gpio.0", 15, "led", 0, GPIO_ACTIVE_HIGH),
GPIO_LOOKUP_IDX("gpio.0", 16, "led", 1, GPIO_ACTIVE_HIGH),
GPIO_LOOKUP_IDX("gpio.0", 17, "led", 2, GPIO_ACTIVE_HIGH),
GPIO_LOOKUP("gpio.0", 1, "power", GPIO_ACTIVE_LOW),
{ },
},
};
And the table can be added by the board code as follows:
And the table can be added by the board code as follows::
gpiod_add_lookup_table(&gpios_table);
The driver controlling "foo.0" will then be able to obtain its GPIOs as follows:
The driver controlling "foo.0" will then be able to obtain its GPIOs as follows::
struct gpio_desc *red, *green, *blue, *power;
......
......@@ -10,6 +10,7 @@ Contents:
intro
driver
consumer
board
legacy
Core
......
......@@ -3,7 +3,5 @@
drivers-on-gpio.txt:
- Drivers in other subsystems that can use GPIO to provide more
complex functionality.
board.txt
- How to assign GPIOs to a consumer device and a function
sysfs.txt
- Information about the GPIO sysfs interface
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