leds-lp55xx: fix problem on removing LED attributes

[mirror_ubuntu-bionic-kernel.git] / Documentation / leds / leds-lp5523.txt

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.
The name of each channel is configurable in the platform data - name and label.
There are three options to make the channel name.

a) Define the 'name' in the platform data
To make specific channel name, then use 'name' platform data.
/sys/class/leds/R1               (name: 'R1')
/sys/class/leds/B1               (name: 'B1')

b) Use the 'label' with no 'name' field
For one device name with channel number, then use 'label'.
/sys/class/leds/RGB:channelN     (label: 'RGB', N: 0 ~ 8)

c) Default
If both fields are NULL, 'lp5523' is used by default.
/sys/class/leds/lp5523:channelN  (N: 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[] = {
        {
		.name		= "D1",
                .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,
};