Documentation: led drivers lp5521 and lp5523

Create sub directory Documentation/leds and add short documentation for
LP5521 and LP5523 drivers.

Signed-off-by: Samu Onkalo <samu.p.onkalo@nokia.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 83 insertions, 0 deletions

diff --git a/Documentation/leds/leds-lp5523.txt b/Documentation/leds/leds-lp5523.txt
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+Kernel driver for lp5523
+========================
+
+* National Semiconductor LP5523 led driver chip
+* Datasheet: http://www.national.com/pf/LP/LP5523.html
+
+Authors: Mathias Nyman, Yuri Zaporozhets, Samu Onkalo
+Contact: Samu Onkalo (samu.p.onkalo-at-nokia.com)
+
+Description
+-----------
+LP5523 can drive up to 9 channels. Leds can be controlled directly via
+the led class control interface. Channels have generic names:
+lp5523:channelx where x is 0...8
+
+The chip provides 3 engines. Each engine can control channels without
+interaction from the main CPU. Details of the micro engine code can be found
+from the public data sheet. Leds can be muxed to different channels.
+
+Control interface for the engines:
+x is 1 .. 3
+enginex_mode : disabled, load, run
+enginex_load : microcode load (visible only in load mode)
+enginex_leds : led mux control (visible only in load mode)
+
+cd /sys/class/leds/lp5523:channel2/device
+echo "load" > engine3_mode
+echo "9d80400004ff05ff437f0000" > engine3_load
+echo "111111111" > engine3_leds
+echo "run" > engine3_mode
+
+sysfs contains a selftest entry. It measures each channel
+voltage level and checks if it looks reasonable. If the level is too high,
+the led is missing; if the level is too low, there is a short circuit.
+
+Selftest uses always the current from the platform data.
+
+Each channel contains led current settings.
+/sys/class/leds/lp5523:channel2/led_current - RW
+/sys/class/leds/lp5523:channel2/max_current - RO
+Format: 10x mA i.e 10 means 1.0 mA
+
+Example platform data:
+
+Note - chan_nr can have values between 0 and 8.
+
+static struct lp5523_led_config lp5523_led_config[] = {
+        {
+                .chan_nr        = 0,
+                .led_current    = 50,
+		.max_current    = 130,
+        },
+...
+        }, {
+                .chan_nr        = 8,
+                .led_current    = 50,
+		.max_current    = 130,
+        }
+};
+
+static int lp5523_setup(void)
+{
+	/* Setup HW resources */
+}
+
+static void lp5523_release(void)
+{
+	/* Release HW resources */
+}
+
+static void lp5523_enable(bool state)
+{
+	/* Control chip enable signal */
+}
+
+static struct lp5523_platform_data lp5523_platform_data = {
+        .led_config     = lp5523_led_config,
+        .num_channels   = ARRAY_SIZE(lp5523_led_config),
+        .clock_mode     = LP5523_CLOCK_EXT,
+        .setup_resources   = lp5523_setup,
+        .release_resources = lp5523_release,
+        .enable            = lp5523_enable,
+};