leds: Introduce userspace LED class driver

This driver creates a userspace leds driver similar to uinput.

New LEDs are created by opening /dev/uleds and writing a uleds_user_dev
struct. A new LED class device is registered with the name given in the
struct. Reading will return a single byte that is the current brightness.
The poll() syscall is also supported. It will be triggered whenever the
brightness changes. Closing the file handle to /dev/uleds will remove
the leds class device.

Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>

include/uapi/linux/Kbuild

@@ -425,6 +425,7 @@ header-y += udp.h
 header-y += uhid.h
 header-y += uinput.h
 header-y += uio.h
+header-y += uleds.h
 header-y += ultrasound.h
 header-y += un.h
 header-y += unistd.h

include/uapi/linux/uleds.h

@@ -0,0 +1,24 @@
+/*
+ * Userspace driver support for the LED subsystem
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#ifndef _UAPI__ULEDS_H_
+#define _UAPI__ULEDS_H_
+
+#define LED_MAX_NAME_SIZE	64
+
+struct uleds_user_dev {
+	char name[LED_MAX_NAME_SIZE];
+	int max_brightness;
+};
+
+#endif /* _UAPI__ULEDS_H_ */