Re: [PATCH] platform/x86: x86-android-tablets: Add a comment about x86_android_tablet_get_gpiod()

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On Mon, Sep 11, 2023 at 11:09 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>
> Add a comment explaining why the special x86_android_tablet_get_gpiod()
> helper is necessary for some of the GPIOs used in the x86-android-tablets;
> and that for normal GPIO lookups this example should not be followed.
>
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> ---
>  drivers/platform/x86/x86-android-tablets/core.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/drivers/platform/x86/x86-android-tablets/core.c b/drivers/platform/x86/x86-android-tablets/core.c
> index 8a1f22aaac00..b55957bde034 100644
> --- a/drivers/platform/x86/x86-android-tablets/core.c
> +++ b/drivers/platform/x86/x86-android-tablets/core.c
> @@ -24,6 +24,21 @@
>
>  static struct platform_device *x86_android_tablet_device;
>
> +/*
> + * This helper allows getting a gpio_desc *before* the actual device consuming
> + * the GPIO has been instantiated. This function _must_ only be used to handle
> + * this special case such as e.g. :
> + *
> + * 1. Getting an IRQ from a GPIO for i2c_board_info.irq which is passed to
> + * i2c_client_new() to instantiate i2c_client-s; or
> + * 2. Calling desc_to_gpio() to get an old style GPIO number for gpio_keys
> + * platform_data which still uses old style GPIO numbers.
> + *
> + * Since the consuming device has not been instatiated yet a dynamic lookup
> + * is generated using the special x86_android_tablet dev for dev_id.
> + *
> + * For normal GPIO lookups a standard static gpiod_lookup_table _must_ be used.
> + */
>  int x86_android_tablet_get_gpiod(const char *chip, int pin, const char *con_id,
>                                  bool active_low, enum gpiod_flags dflags,
>                                  struct gpio_desc **desc)
> --
> 2.41.0
>

Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>




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