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>
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@ -295,10 +295,6 @@ These GPIO numbers are controller relative and path "\\_SB.PCI0.GPI0"
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specifies the path to the controller. In order to use these GPIOs in Linux
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specifies the path to the controller. In order to use these GPIOs in Linux
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we need to translate them to the Linux GPIO numbers.
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we need to translate them to the Linux GPIO numbers.
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The driver can do this by including <linux/acpi_gpio.h> and then calling
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acpi_get_gpio(path, gpio). This will return the Linux GPIO number or
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negative errno if there was no translation found.
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In a simple case of just getting the Linux GPIO number from device
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In a simple case of just getting the Linux GPIO number from device
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resources one can use acpi_get_gpio_by_index() helper function. It takes
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resources one can use acpi_get_gpio_by_index() helper function. It takes
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pointer to the device and index of the GpioIo/GpioInt descriptor in the
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pointer to the device and index of the GpioIo/GpioInt descriptor in the
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@ -322,3 +318,25 @@ suitable to the gpiolib before passing them.
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In case of GpioInt resource an additional call to gpio_to_irq() must be
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In case of GpioInt resource an additional call to gpio_to_irq() must be
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done before calling request_irq().
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done before calling request_irq().
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Note that the above API is ACPI specific and not recommended for drivers
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that need to support non-ACPI systems. The recommended way is to use
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the descriptor based GPIO interfaces. The above example looks like this
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when converted to the GPIO desc:
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#include <linux/gpio/consumer.h>
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...
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struct gpio_desc *irq_desc, *power_desc;
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irq_desc = gpiod_get_index(dev, NULL, 1);
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if (IS_ERR(irq_desc))
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/* handle error */
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power_desc = gpiod_get_index(dev, NULL, 0);
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if (IS_ERR(power_desc))
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/* handle error */
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/* Now we can use the GPIO descriptors */
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See also Documentation/gpio.txt.
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