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gpiolib / ACPI: document the GPIO descriptor based interface 

In addition to the existing ACPI specific GPIO interface, document the new
descriptor based GPIO interface in Documentation/acpi/enumeration.txt, so
it is clear that this new interface is preferred over the ACPI specific
version.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
hifive-unleashed-5.1
Mika Westerberg 2013-10-10 11:01:11 +03:00 committed by Linus Walleij
parent e01f440a68
commit 45f394391f
1 changed files with 22 additions and 4 deletions
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26
Documentation/acpi/enumeration.txt
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@ -295,10 +295,6 @@ 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.
The driver can do this by including <linux/acpi_gpio.h> and then calling
acpi_get_gpio(path, gpio). This will return the Linux GPIO number or
negative errno if there was no translation found.
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
@ -322,3 +318,25 @@ 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:
#include <linux/gpio/consumer.h>
...
struct gpio_desc *irq_desc, *power_desc;
irq_desc = gpiod_get_index(dev, NULL, 1);
if (IS_ERR(irq_desc))
/* handle error */
power_desc = gpiod_get_index(dev, NULL, 0);
if (IS_ERR(power_desc))
/* handle error */
/* Now we can use the GPIO descriptors */
See also Documentation/gpio.txt.