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authorAlexandre Courbot <acourbot@nvidia.com>2013-12-03 12:20:11 +0900
committerLinus Walleij <linus.walleij@linaro.org>2013-12-09 14:05:51 +0100
commitad824783fb23bbc8295cffb6214b3b82d25f7d4a (patch)
tree745d128c1d04dca7a6c7b10dd737f116f13ddcb1 /Documentation/gpio
parentbdc54ef45d7670aeb52ce73f8b7ad5f3e5563661 (diff)
gpio: better lookup method for platform GPIOs
Change the format of the platform GPIO lookup tables to make them less confusing and improve lookup efficiency. The previous format was a single linked-list that required to compare the device name and function ID of every single GPIO defined for each lookup. Switch that to a list of per-device tables, so that the lookup can be done in two steps, omitting the GPIOs that are not relevant for a particular device. The matching rules are now defined as follows: - The device name must match *exactly*, and can be NULL for GPIOs not assigned to a particular device, - If the function ID in the lookup table is NULL, the con_id argument of gpiod_get() will not be used for lookup. However, if it is defined, it must match exactly. - The index must always match. Signed-off-by: Alexandre Courbot <acourbot@nvidia.com> Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'Documentation/gpio')
-rw-r--r--Documentation/gpio/board.txt28
1 files changed, 17 insertions, 11 deletions
diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt
index 0d03506f2cc5..ba169faad5c6 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:

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