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Documentation / ACPI: update to GPIO descriptor API 

Update the documentation also to reflect the fact that there are no ACPI
specific GPIO interfaces anymore but drivers should instead use the
descriptor based GPIO APIs.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
wifi-calibration
Mika Westerberg 2014-01-08 12:40:57 +02:00 committed by Linus Walleij
parent 5ccff85276
commit ccb6fbb990
1 changed files with 7 additions and 29 deletions
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36
Documentation/acpi/enumeration.txt
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@ -293,36 +293,13 @@ the device to the driver. For example:
These GPIO numbers are controller relative and path "\\_SB.PCI0.GPI0"
specifies the path to the controller. In order to use these GPIOs in Linux
we need to translate them to the Linux GPIO numbers.
we need to translate them to the corresponding Linux GPIO descriptors.
In a simple case of just getting the Linux GPIO number from device
resources one can use acpi_get_gpio_by_index() helper function. It takes
pointer to the device and index of the GpioIo/GpioInt descriptor in the
device resources list. For example:
There is a standard GPIO API for that and is documented in
Documentation/gpio.txt.
int gpio_irq, gpio_power;
int ret;
gpio_irq = acpi_get_gpio_by_index(dev, 1, NULL);
if (gpio_irq < 0)
/* handle error */
gpio_power = acpi_get_gpio_by_index(dev, 0, NULL);
if (gpio_power < 0)
/* handle error */
/* Now we can use the GPIO numbers */
Other GpioIo parameters must be converted first by the driver to be
suitable to the gpiolib before passing them.
In case of GpioInt resource an additional call to gpio_to_irq() must be
done before calling request_irq().
Note that the above API is ACPI specific and not recommended for drivers
that need to support non-ACPI systems. The recommended way is to use
the descriptor based GPIO interfaces. The above example looks like this
when converted to the GPIO desc:
In the above example we can get the corresponding two GPIO descriptors with
a code like this:
#include <linux/gpio/consumer.h>
...
@ -339,4 +316,5 @@ when converted to the GPIO desc:
/* Now we can use the GPIO descriptors */
See also Documentation/gpio.txt.
There are also devm_* versions of these functions which release the
descriptors once the device is released.