gianfar: fix signedness issue

[net-next-2.6.git] / Documentation / leds / leds-lp5521.txt

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.