leds: Add driver for LT3593 controlled LEDs

The LT3593 is a step-up DC/DC converter designed to drive up to ten
white LEDs in series. The current flow can be set with a control pin.

This driver controls any number of such devices connected on generic
GPIOs and exports the function as as platform_driver.

The gpio_led platform data struct definition is reused for this purpose.

Successfully tested on a PXA embedded board.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index e481d3c..e2b7a53 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -245,6 +245,14 @@
 	  drive or power LEDs on the front panel.  Using this driver
 	  can stop the front LED from blinking after startup.
 
+config LEDS_LT3593
+	tristate "LED driver for LT3593 controllers"
+	depends on LEDS_CLASS && GENERIC_GPIO
+	help
+	  This option enables support for LEDs driven by a Linear Technology
+	  LT3593 controller. This controller uses a special one-wire pulse
+	  coding protocol to set the brightness.
+
 comment "LED Triggers"
 
 config LEDS_TRIGGERS