gpio: add GPIO hogging mechanism

Based on Boris Brezillion's work this is a reworked patch
of his initial GPIO hogging mechanism.
This patch provides a way to initially configure specific GPIO
when the GPIO controller is probed.

The actual DT scanning to collect the GPIO specific data is performed
as part of gpiochip_add().

The purpose of this is to allow specific GPIOs to be configured
without any driver specific code.
This is particularly useful because board design are getting
increasingly complex and given SoC pins can now have more
than 10 mux values, a lot of connections are now dependent on
external IO muxes to switch various modes.

Specific drivers should not necessarily need to be aware of
what accounts to a specific board implementation. This board level
"description" should be best kept as part of the dts file.

Signed-off-by: Benoit Parrot <bparrot@ti.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 550a5eafbd38..cadba26c45a6 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -78,6 +78,7 @@ struct gpio_desc {
 #define FLAG_OPEN_SOURCE 8	/* Gpio is open source type */
 #define FLAG_USED_AS_IRQ 9	/* GPIO is connected to an IRQ */
 #define FLAG_SYSFS_DIR	10	/* show sysfs direction attribute */
+#define FLAG_IS_HOGGED	11	/* GPIO is hogged */
 
 #define ID_SHIFT	16	/* add new flags before this one */
 
@@ -89,6 +90,8 @@ struct gpio_desc {
 
 int gpiod_request(struct gpio_desc *desc, const char *label);
 void gpiod_free(struct gpio_desc *desc);
+int gpiod_hog(struct gpio_desc *desc, const char *name,
+		unsigned long lflags, enum gpiod_flags dflags);
 
 /*
  * Return the GPIO number of the passed descriptor relative to its chip