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gpio: better lookup method for platform GPIOs

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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 <[email protected]>
Acked-by: Mika Westerberg <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>
This commit is contained in:
Alexandre Courbot 2013-12-03 12:20:11 +09:00 • committed by Linus Walleij
commit ad824783fb
3 changed files with 85 additions and 72 deletions
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28
Documentation/gpio/board.txt
View file

@ -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: