linux/Documentation/leds/leds-lp55xx.txt
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   1LP5521/LP5523/LP55231 Common Driver
   2===================================
   3
   4Authors: Milo(Woogyom) Kim <milo.kim@ti.com>
   5
   6Description
   7-----------
   8LP5521, LP5523/55231 and LP5562 have common features as below.
   9
  10  Register access via the I2C
  11  Device initialization/deinitialization
  12  Create LED class devices for multiple output channels
  13  Device attributes for user-space interface
  14  Program memory for running LED patterns
  15
  16The LP55xx common driver provides these features using exported functions.
  17  lp55xx_init_device() / lp55xx_deinit_device()
  18  lp55xx_register_leds() / lp55xx_unregister_leds()
  19  lp55xx_regsister_sysfs() / lp55xx_unregister_sysfs()
  20
  21( Driver Structure Data )
  22
  23In lp55xx common driver, two different data structure is used.
  24
  25o lp55xx_led
  26  control multi output LED channels such as led current, channel index.
  27o lp55xx_chip
  28  general chip control such like the I2C and platform data.
  29
  30For example, LP5521 has maximum 3 LED channels.
  31LP5523/55231 has 9 output channels.
  32
  33lp55xx_chip for LP5521 ... lp55xx_led #1
  34                           lp55xx_led #2
  35                           lp55xx_led #3
  36
  37lp55xx_chip for LP5523 ... lp55xx_led #1
  38                           lp55xx_led #2
  39                                 .
  40                                 .
  41                           lp55xx_led #9
  42
  43( Chip Dependent Code )
  44
  45To support device specific configurations, special structure
  46'lpxx_device_config' is used.
  47
  48  Maximum number of channels
  49  Reset command, chip enable command
  50  Chip specific initialization
  51  Brightness control register access
  52  Setting LED output current
  53  Program memory address access for running patterns
  54  Additional device specific attributes
  55
  56( Firmware Interface )
  57
  58LP55xx family devices have the internal program memory for running
  59various LED patterns.
  60This pattern data is saved as a file in the user-land or
  61hex byte string is written into the memory through the I2C.
  62LP55xx common driver supports the firmware interface.
  63
  64LP55xx chips have three program engines.
  65To load and run the pattern, the programming sequence is following.
  66  (1) Select an engine number (1/2/3)
  67  (2) Mode change to load
  68  (3) Write pattern data into selected area
  69  (4) Mode change to run
  70
  71The LP55xx common driver provides simple interfaces as below.
  72select_engine : Select which engine is used for running program
  73run_engine    : Start program which is loaded via the firmware interface
  74firmware      : Load program data
  75
  76For example, run blinking pattern in engine #1 of LP5521
  77echo 1 > /sys/bus/i2c/devices/xxxx/select_engine
  78echo 1 > /sys/class/firmware/lp5521/loading
  79echo "4000600040FF6000" > /sys/class/firmware/lp5521/data
  80echo 0 > /sys/class/firmware/lp5521/loading
  81echo 1 > /sys/bus/i2c/devices/xxxx/run_engine
  82
  83For example, run blinking pattern in engine #3 of LP55231
  84echo 3 > /sys/bus/i2c/devices/xxxx/select_engine
  85echo 1 > /sys/class/firmware/lp55231/loading
  86echo "9d0740ff7e0040007e00a0010000" > /sys/class/firmware/lp55231/data
  87echo 0 > /sys/class/firmware/lp55231/loading
  88echo 1 > /sys/bus/i2c/devices/xxxx/run_engine
  89
  90To start blinking patterns in engine #2 and #3 simultaneously,
  91for idx in 2 3
  92do
  93  echo $idx > /sys/class/leds/red/device/select_engine
  94  sleep 0.1
  95  echo 1 > /sys/class/firmware/lp5521/loading
  96  echo "4000600040FF6000" > /sys/class/firmware/lp5521/data
  97  echo 0 > /sys/class/firmware/lp5521/loading
  98done
  99echo 1 > /sys/class/leds/red/device/run_engine
 100
 101Here is another example for LP5523.
 102echo 2 > /sys/bus/i2c/devices/xxxx/select_engine
 103echo 1 > /sys/class/firmware/lp5523/loading
 104echo "9d80400004ff05ff437f0000" > /sys/class/firmware/lp5523/data
 105echo 0 > /sys/class/firmware/lp5523/loading
 106echo 1 > /sys/bus/i2c/devices/xxxx/run_engine
 107
 108As soon as 'loading' is set to 0, registered callback is called.
 109Inside the callback, the selected engine is loaded and memory is updated.
 110To run programmed pattern, 'run_engine' attribute should be enabled.
 111
 112( 'run_engine' and 'firmware_cb' )
 113The sequence of running the program data is common.
 114But each device has own specific register addresses for commands.
 115To support this, 'run_engine' and 'firmware_cb' are configurable in each driver.
 116run_engine  : Control the selected engine
 117firmware_cb : The callback function after loading the firmware is done.
 118              Chip specific commands for loading and updating program memory.
 119
 120( Predefined pattern data )
 121
 122Without the firmware interface, LP55xx driver provides another method for
 123loading a LED pattern. That is 'predefined' pattern.
 124A predefined pattern is defined in the platform data and load it(or them)
 125via the sysfs if needed.
 126To use the predefined pattern concept, 'patterns' and 'num_patterns' should be
 127configured.
 128
 129  Example of predefined pattern data:
 130
 131  /* mode_1: blinking data */
 132  static const u8 mode_1[] = {
 133                0x40, 0x00, 0x60, 0x00, 0x40, 0xFF, 0x60, 0x00,
 134                };
 135
 136  /* mode_2: always on */
 137  static const u8 mode_2[] = { 0x40, 0xFF, };
 138
 139  struct lp55xx_predef_pattern board_led_patterns[] = {
 140        {
 141                .r = mode_1,
 142                .size_r = ARRAY_SIZE(mode_1),
 143        },
 144        {
 145                .b = mode_2,
 146                .size_b = ARRAY_SIZE(mode_2),
 147        },
 148  }
 149
 150  struct lp55xx_platform_data lp5562_pdata = {
 151  ...
 152        .patterns      = board_led_patterns,
 153        .num_patterns  = ARRAY_SIZE(board_led_patterns),
 154  };
 155
 156Then, mode_1 and mode_2 can be run via through the sysfs.
 157
 158  echo 1 > /sys/bus/i2c/devices/xxxx/led_pattern    # red blinking LED pattern
 159  echo 2 > /sys/bus/i2c/devices/xxxx/led_pattern    # blue LED always on
 160
 161To stop running pattern,
 162  echo 0 > /sys/bus/i2c/devices/xxxx/led_pattern
 163
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