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>
