Documentation: leds: update LP55xx family devices

 Update changed platform data information.
 Add leds-lp55xx.txt which includes the firmware interface description.

Signed-off-by: Milo(Woogyom) Kim <milo.kim@ti.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>

1 files changed, 118 insertions, 0 deletions

diff --git a/Documentation/leds/leds-lp55xx.txt b/Documentation/leds/leds-lp55xx.txt
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+LP5521/LP5523/LP55231 Common Driver
+===================================
+
+Authors: Milo(Woogyom) Kim <milo.kim@ti.com>
+
+Description
+-----------
+LP5521, LP5523/55231 have common features as below.
+
+  Register access via the I2C
+  Device initialization/deinitialization
+  Create LED class devices for multiple output channels
+  Device attributes for user-space interface
+  Program memory for running LED patterns
+
+The LP55xx common driver provides these features using exported functions.
+  lp55xx_init_device() / lp55xx_deinit_device()
+  lp55xx_register_leds() / lp55xx_unregister_leds()
+  lp55xx_regsister_sysfs() / lp55xx_unregister_sysfs()
+
+( Driver Structure Data )
+
+In lp55xx common driver, two different data structure is used.
+
+o lp55xx_led
+  control multi output LED channels such as led current, channel index.
+o lp55xx_chip
+  general chip control such like the I2C and platform data.
+
+For example, LP5521 has maximum 3 LED channels.
+LP5523/55231 has 9 output channels.
+
+lp55xx_chip for LP5521 ... lp55xx_led #1
+                           lp55xx_led #2
+                           lp55xx_led #3
+
+lp55xx_chip for LP5523 ... lp55xx_led #1
+                           lp55xx_led #2
+                                 .
+                                 .
+                           lp55xx_led #9
+
+( Chip Dependent Code )
+
+To support device specific configurations, special structure
+'lpxx_device_config' is used.
+
+  Maximum number of channels
+  Reset command, chip enable command
+  Chip specific initialization
+  Brightness control register access
+  Setting LED output current
+  Program memory address access for running patterns
+  Additional device specific attributes
+
+( Firmware Interface )
+
+LP55xx family devices have the internal program memory for running
+various LED patterns.
+This pattern data is saved as a file in the user-land or
+hex byte string is written into the memory through the I2C.
+LP55xx common driver supports the firmware interface.
+
+LP55xx chips have three program engines.
+To load and run the pattern, the programming sequence is following.
+  (1) Select an engine number (1/2/3)
+  (2) Mode change to load
+  (3) Write pattern data into selected area
+  (4) Mode change to run
+
+The LP55xx common driver provides simple interfaces as below.
+select_engine : Select which engine is used for running program
+run_engine    : Start program which is loaded via the firmware interface
+firmware      : Load program data
+
+For example, run blinking pattern in engine #1 of LP5521
+echo 1 > /sys/bus/i2c/devices/xxxx/select_engine
+echo 1 > /sys/class/firmware/lp5521/loading
+echo "4000600040FF6000" > /sys/class/firmware/lp5521/data
+echo 0 > /sys/class/firmware/lp5521/loading
+echo 1 > /sys/bus/i2c/devices/xxxx/run_engine
+
+For example, run blinking pattern in engine #3 of LP55231
+echo 3 > /sys/bus/i2c/devices/xxxx/select_engine
+echo 1 > /sys/class/firmware/lp55231/loading
+echo "9d0740ff7e0040007e00a0010000" > /sys/class/firmware/lp55231/data
+echo 0 > /sys/class/firmware/lp55231/loading
+echo 1 > /sys/bus/i2c/devices/xxxx/run_engine
+
+To start blinking patterns in engine #2 and #3 simultaneously,
+for idx in 2 3
+do
+  echo $idx > /sys/class/leds/red/device/select_engine
+  sleep 0.1
+  echo 1 > /sys/class/firmware/lp5521/loading
+  echo "4000600040FF6000" > /sys/class/firmware/lp5521/data
+  echo 0 > /sys/class/firmware/lp5521/loading
+done
+echo 1 > /sys/class/leds/red/device/run_engine
+
+Here is another example for LP5523.
+echo 2 > /sys/bus/i2c/devices/xxxx/select_engine
+echo 1 > /sys/class/firmware/lp5523/loading
+echo "9d80400004ff05ff437f0000" > /sys/class/firmware/lp5523/data
+echo 0 > /sys/class/firmware/lp5523/loading
+echo 1 > /sys/bus/i2c/devices/xxxx/run_engine
+
+As soon as 'loading' is set to 0, registered callback is called.
+Inside the callback, the selected engine is loaded and memory is updated.
+To run programmed pattern, 'run_engine' attribute should be enabled.
+
+( 'run_engine' and 'firmware_cb' )
+The sequence of running the program data is common.
+But each device has own specific register addresses for commands.
+To support this, 'run_engine' and 'firmware_cb' are configurable in each driver.
+run_engine  : Control the selected engine
+firmware_cb : The callback function after loading the firmware is done.
+              Chip specific commands for loading and updating program memory.