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, 88 insertions, 0 deletions

diff --git a/Documentation/leds/leds-lp5521.txt b/Documentation/leds/leds-lp5521.txt
new file mode 100644
index 000000000000..c4d8d151e0fe
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+++ b/Documentation/leds/leds-lp5521.txt
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+Kernel driver for lp5521
+========================
+
+* National Semiconductor LP5521 led driver chip
+* Datasheet: http://www.national.com/pf/LP/LP5521.html
+
+Authors: Mathias Nyman, Yuri Zaporozhets, Samu Onkalo
+Contact: Samu Onkalo (samu.p.onkalo-at-nokia.com)
+
+Description
+-----------
+
+LP5521 can drive up to 3 channels. Leds can be controlled directly via
+the led class control interface. Channels have generic names:
+lp5521:channelx, where x is 0 .. 2
+
+All three channels can be also controlled using the engine micro programs.
+More details of the instructions can be found from the public data sheet.
+
+Control interface for the engines:
+x is 1 .. 3
+enginex_mode : disabled, load, run
+enginex_load : store program (visible only in engine load mode)
+
+Example (start to blink the channel 2 led):
+cd   /sys/class/leds/lp5521:channel2/device
+echo "load" > engine3_mode
+echo "037f4d0003ff6000" > engine3_load
+echo "run" > engine3_mode
+
+stop the engine:
+echo "disabled" > engine3_mode
+
+sysfs contains a selftest entry.
+The test communicates with the chip and checks that
+the clock mode is automatically set to the requested one.
+
+Each channel has its own led current settings.
+/sys/class/leds/lp5521:channel0/led_current - RW
+/sys/class/leds/lp5521:channel0/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 2.
+
+static struct lp5521_led_config lp5521_led_config[] = {
+        {
+                .chan_nr        = 0,
+                .led_current    = 50,
+		.max_current    = 130,
+        }, {
+                .chan_nr        = 1,
+                .led_current    = 0,
+		.max_current    = 130,
+        }, {
+                .chan_nr        = 2,
+                .led_current    = 0,
+		.max_current    = 130,
+        }
+};
+
+static int lp5521_setup(void)
+{
+	/* setup HW resources */
+}
+
+static void lp5521_release(void)
+{
+	/* Release HW resources */
+}
+
+static void lp5521_enable(bool state)
+{
+	/* Control of chip enable signal */
+}
+
+static struct lp5521_platform_data lp5521_platform_data = {
+        .led_config     = lp5521_led_config,
+        .num_channels   = ARRAY_SIZE(lp5521_led_config),
+        .clock_mode     = LP5521_CLOCK_EXT,
+        .setup_resources   = lp5521_setup,
+        .release_resources = lp5521_release,
+        .enable            = lp5521_enable,
+};
+
+If the current is set to 0 in the platform data, that channel is
+disabled and it is not visible in the sysfs.