leds: rt8515: Add Richtek RT8515 LED driver

This adds a driver for the Richtek RT8515 dual channel
torch/flash white LED driver.

This LED driver is found in some mobile phones from
Samsung such as the GT-S7710 and GT-I8190.

A V4L interface is added.

We do not have a proper datasheet for the RT8515 but
it turns out that RT9387A has a public datasheet and
is essentially the same chip. We designed the driver
in accordance with this datasheet. The day someone
needs to drive a RT9387A this driver can probably
easily be augmented to handle that chip too.

Sakari Ailus, Pavel Machek and Andy Shevchenko helped
significantly in getting this driver right.

Cc: Sakari Ailus <sakari.ailus@iki.fi>
Cc: newbytee@protonmail.com
Cc: Stephan Gerhold <stephan@gerhold.net>
Cc: linux-media@vger.kernel.org
Cc: phone-devel@vger.kernel.org
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>

drivers/leds/Kconfig

@@ -928,6 +928,9 @@ config LEDS_ACER_A500
 	  This option enables support for the Power Button LED of
 	  Acer Iconia Tab A500.
 
+comment "Flash and Torch LED drivers"
+source "drivers/leds/flash/Kconfig"
+
 comment "LED Triggers"
 source "drivers/leds/trigger/Kconfig"
 

drivers/leds/Makefile

@@ -103,5 +103,8 @@ obj-$(CONFIG_LEDS_SPI_BYTE)		+= leds-spi-byte.o
 # LED Userspace Drivers
 obj-$(CONFIG_LEDS_USER)			+= uleds.o
 
+# Flash and Torch LED Drivers
+obj-$(CONFIG_LEDS_CLASS_FLASH)		+= flash/
+
 # LED Triggers
 obj-$(CONFIG_LEDS_TRIGGERS)		+= trigger/

drivers/leds/flash/Kconfig

+# SPDX-License-Identifier: GPL-2.0
+
+if LEDS_CLASS_FLASH
+
+config LEDS_RT8515
+	tristate "LED support for Richtek RT8515 flash/torch LED"
+	depends on GPIOLIB
+	help
+	  This option enables support for the Richtek RT8515 flash
+	  and torch LEDs found on some mobile phones.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called leds-rt8515.
+
+endif # LEDS_CLASS_FLASH

drivers/leds/flash/Makefile

+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_LEDS_RT8515)	+= leds-rt8515.o