Commit eee9cd5d authored by Hans de Goede's avatar Hans de Goede
Browse files

platform/x86: x86-android-tablets: Add a comment about x86_android_tablet_get_gpiod() 



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: default avatarHans de Goede <hdegoede@redhat.com>
Reviewed-by: default avatarBartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://lore.kernel.org/r/20230911210928.264908-1-hdegoede@redhat.com
parent 9578db79

drivers/platform/x86/x86-android-tablets/core.c

+15 −0
Original line number Diff line number Diff line
@@ -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)