diff options
Diffstat (limited to 'Documentation/gpio')
| -rw-r--r-- | Documentation/gpio/00-INDEX | 14 | ||||
| -rw-r--r-- | Documentation/gpio/board.txt | 28 | ||||
| -rw-r--r-- | Documentation/gpio/consumer.txt | 6 |
3 files changed, 36 insertions, 12 deletions
diff --git a/Documentation/gpio/00-INDEX b/Documentation/gpio/00-INDEX new file mode 100644 index 00000000000..1de43ae46ae --- /dev/null +++ b/Documentation/gpio/00-INDEX @@ -0,0 +1,14 @@ +00-INDEX + - This file +gpio.txt + - Introduction to GPIOs and their kernel interfaces +consumer.txt + - How to obtain and use GPIOs in a driver +driver.txt + - How to write a GPIO driver +board.txt + - How to assign GPIOs to a consumer device and a function +sysfs.txt + - Information about the GPIO sysfs interface +gpio-legacy.txt + - Historical documentation of the deprecated GPIO integer interface diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt index 0d03506f2cc..ba169faad5c 100644 --- a/Documentation/gpio/board.txt +++ b/Documentation/gpio/board.txt @@ -72,10 +72,11 @@ where - chip_label is the label of the gpiod_chip instance providing the GPIO - chip_hwnum is the hardware number of the GPIO within the chip - - dev_id is the identifier of the device that will make use of this GPIO. If - NULL, the GPIO will be available to all devices. + - dev_id is the identifier of the device that will make use of this GPIO. It + can be NULL, in which case it will be matched for calls to gpiod_get() + with a NULL device. - con_id is the name of the GPIO function from the device point of view. It - can be NULL. + can be NULL, in which case it will match any function. - idx is the index of the GPIO within the function. - flags is defined to specify the following properties: * GPIOF_ACTIVE_LOW - to configure the GPIO as active-low @@ -86,18 +87,23 @@ In the future, these flags might be extended to support more properties. Note that GPIO_LOOKUP() is just a shortcut to GPIO_LOOKUP_IDX() where idx = 0. -A lookup table can then be defined as follows: +A lookup table can then be defined as follows, with an empty entry defining its +end: - struct gpiod_lookup gpios_table[] = { - GPIO_LOOKUP_IDX("gpio.0", 15, "foo.0", "led", 0, GPIO_ACTIVE_HIGH), - GPIO_LOOKUP_IDX("gpio.0", 16, "foo.0", "led", 1, GPIO_ACTIVE_HIGH), - GPIO_LOOKUP_IDX("gpio.0", 17, "foo.0", "led", 2, GPIO_ACTIVE_HIGH), - GPIO_LOOKUP("gpio.0", 1, "foo.0", "power", GPIO_ACTIVE_LOW), - }; +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: - gpiod_add_table(gpios_table, ARRAY_SIZE(gpios_table)); + gpiod_add_lookup_table(&gpios_table); The driver controlling "foo.0" will then be able to obtain its GPIOs as follows: diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt index 07c74a3765a..e42f77d8d4c 100644 --- a/Documentation/gpio/consumer.txt +++ b/Documentation/gpio/consumer.txt @@ -38,7 +38,11 @@ device that displays digits), an additional index argument can be specified: const char *con_id, unsigned int idx) Both functions return either a valid GPIO descriptor, or an error code checkable -with IS_ERR(). They will never return a NULL pointer. +with IS_ERR() (they will never return a NULL pointer). -ENOENT will be returned +if and only if no GPIO has been assigned to the device/function/index triplet, +other error codes are used for cases where a GPIO has been assigned but an error +occured while trying to acquire it. This is useful to discriminate between mere +errors and an absence of GPIO for optional GPIO parameters. Device-managed variants of these functions are also defined: |