On Tuesday, March 17, 2015 12:40:12 PM Mika Westerberg wrote:
> Make sure that the ACPI enumeration.txt provides latest information on how
> to describe and retrieve GPIOs now that we can take advantage of _DSD
> device properties.
>
> Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Queued up for 4.1, thanks!
> ---
> Documentation/acpi/enumeration.txt | 26 +++++++++++++++++++++++---
> 1 file changed, 23 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/acpi/enumeration.txt b/Documentation/acpi/enumeration.txt
> index 9b121a569ab4..750401f91341 100644
> --- a/Documentation/acpi/enumeration.txt
> +++ b/Documentation/acpi/enumeration.txt
> @@ -254,8 +254,13 @@ GPIO support
> ~~~~~~~~~~~~
> ACPI 5 introduced two new resources to describe GPIO connections: GpioIo
> and GpioInt. These resources are used be used to pass GPIO numbers used by
> -the device to the driver. For example:
> +the device to the driver. ACPI 5.1 extended this with _DSD (Device
> +Specific Data) which made it possible to name the GPIOs among other things.
>
> +For example:
> +
> +Device (DEV)
> +{
> Method (_CRS, 0, NotSerialized)
> {
> Name (SBUF, ResourceTemplate()
> @@ -285,6 +290,18 @@ the device to the driver. For example:
> Return (SBUF)
> }
>
> + // ACPI 5.1 _DSD used for naming the GPIOs
> + Name (_DSD, Package ()
> + {
> + ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
> + Package ()
> + {
> + Package () {"power-gpios", Package() {^DEV, 0, 0, 0 }},
> + Package () {"irq-gpios", Package() {^DEV, 1, 0, 0 }},
> + }
> + })
> + ...
> +
> 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 corresponding Linux GPIO descriptors.
> @@ -300,11 +317,11 @@ a code like this:
>
> struct gpio_desc *irq_desc, *power_desc;
>
> - irq_desc = gpiod_get_index(dev, NULL, 1);
> + irq_desc = gpiod_get(dev, "irq");
> if (IS_ERR(irq_desc))
> /* handle error */
>
> - power_desc = gpiod_get_index(dev, NULL, 0);
> + power_desc = gpiod_get(dev, "power");
> if (IS_ERR(power_desc))
> /* handle error */
>
> @@ -313,6 +330,9 @@ a code like this:
> There are also devm_* versions of these functions which release the
> descriptors once the device is released.
>
> +See Documentation/acpi/gpio-properties.txt for more information about the
> +_DSD binding related to GPIOs.
> +
> MFD devices
> ~~~~~~~~~~~
> The MFD devices register their children as platform devices. For the child
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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