+=============
GPIO Mappings
=============
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";
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;
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 () {
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)
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;