On Thu, Nov 12, 2020 at 10:02:41AM +0100, Flavio Suligoi wrote:
> The "gpio-line-names" declaration is not fully
> documented, so can be useful to add some important
> information and one more example.
>
> This commit also fixes a trivial spelling mistake.
Thanks!
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Signed-off-by: Flavio Suligoi <f.suligoi@xxxxxxx>
> ---
>
> v2: - fix commit spelling mistakes
> - add double back quotes to gpio-line-names
> - adjust documentation lines layout
> - add comma at the end of Package list names in the first example
>
> .../firmware-guide/acpi/gpio-properties.rst | 58 ++++++++++++++++++-
> 1 file changed, 56 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/firmware-guide/acpi/gpio-properties.rst b/Documentation/firmware-guide/acpi/gpio-properties.rst
> index bb6d74f23ee0..ae5396a1f092 100644
> --- a/Documentation/firmware-guide/acpi/gpio-properties.rst
> +++ b/Documentation/firmware-guide/acpi/gpio-properties.rst
> @@ -107,7 +107,61 @@ Example::
>
> - gpio-line-names
>
> -Example::
> +The ``gpio-line-names`` declaration is a list of strings ("names"), which
> +describes each line/pin of a GPIO controller/expander. This list, contained in
> +a package, must be inserted inside the GPIO controller declaration of an ACPI
> +table (typically inside the DSDT). The ``gpio-line-names`` list must respect the
> +following rules (see also the examples):
> +
> + - the first name in the list corresponds with the first line/pin of the GPIO
> + controller/expander
> + - the names inside the list must be consecutive (no "holes" are permitted)
> + - the list can be incomplete and can end before the last GPIO line: in
> + other words, it is not mandatory to fill all the GPIO lines
> + - empty names are allowed (two quotation marks ``""`` correspond to an empty
> + name)
> +
> +Example of a GPIO controller of 16 lines, with an incomplete list with two
> +empty names::
> +
> + Package () {
> + "gpio-line-names",
> + Package () {
> + "pin_0",
> + "pin_1",
> + "",
> + "",
> + "pin_3",
> + "pin_4_push_button",
> + }
> + }
> +
> +At runtime, the above declaration produces the following result (using the
> +"libgpiod" tools)::
> +
> + root@debian:~# gpioinfo gpiochip4
> + gpiochip4 - 16 lines:
> + line 0: "pin_0" unused input active-high
> + line 1: "pin_1" unused input active-high
> + line 2: unnamed unused input active-high
> + line 3: unnamed unused input active-high
> + line 4: "pin_3" unused input active-high
> + line 5: "pin_4_push_button" unused input active-high
> + line 6: unnamed unused input active-high
> + line 7 unnamed unused input active-high
> + line 8: unnamed unused input active-high
> + line 9: unnamed unused input active-high
> + line 10: unnamed unused input active-high
> + line 11: unnamed unused input active-high
> + line 12: unnamed unused input active-high
> + line 13: unnamed unused input active-high
> + line 14: unnamed unused input active-high
> + line 15: unnamed unused input active-high
> + root@debian:~# gpiofind pin_4_push_button
> + gpiochip4 5
> + root@debian:~#
> +
> +Another example::
>
> Package () {
> "gpio-line-names",
> @@ -191,7 +245,7 @@ The driver might expect to get the right GPIO when it does::
> but since there is no way to know the mapping between "reset" and
> the GpioIo() in _CRS desc will hold ERR_PTR(-ENOENT).
>
> -The driver author can solve this by passing the mapping explictly
> +The driver author can solve this by passing the mapping explicitly
> (the recommended way and documented in the above chapter).
>
> The ACPI GPIO mapping tables should not contaminate drivers that are not
> --
> 2.25.1
>
--
With Best Regards,
Andy Shevchenko
