Documentation/leds/leds-lp3944.txt

   1 Kernel driver lp3944
   2 ====================
   3
   4   * National Semiconductor LP3944 Fun-light Chip
   5     Prefix: 'lp3944'
   6     Addresses scanned: None (see the Notes section below)
   7     Datasheet: Publicly available at the National Semiconductor website
   8                http://www.national.com/pf/LP/LP3944.html
   9
  10 Authors:
  11         Antonio Ospite <ospite@studenti.unina.it>
  12
  13
  14 Description
  15 -----------
  16 The LP3944 is a helper chip that can drive up to 8 leds, with two programmable
  17 DIM modes; it could even be used as a gpio expander but this driver assumes it
  18 is used as a led controller.
  19
  20 The DIM modes are used to set _blink_ patterns for leds, the pattern is
  21 specified supplying two parameters:
  22   - period: from 0s to 1.6s
  23   - duty cycle: percentage of the period the led is on, from 0 to 100
  24
  25 Setting a led in DIM0 or DIM1 mode makes it blink according to the pattern.
  26 See the datasheet for details.
  27
  28 LP3944 can be found on Motorola A910 smartphone, where it drives the rgb
  29 leds, the camera flash light and the lcds power.
  30
  31
  32 Notes
  33 -----
  34 The chip is used mainly in embedded contexts, so this driver expects it is
  35 registered using the i2c_board_info mechanism.
  36
  37 To register the chip at address 0x60 on adapter 0, set the platform data
  38 according to include/linux/leds-lp3944.h, set the i2c board info:
  39
  40         static struct i2c_board_info a910_i2c_board_info[] __initdata = {
  41                 {
  42                         I2C_BOARD_INFO("lp3944", 0x60),
  43                         .platform_data = &a910_lp3944_leds,
  44                 },
  45         };
  46
  47 and register it in the platform init function
  48
  49         i2c_register_board_info(0, a910_i2c_board_info,
  50                         ARRAY_SIZE(a910_i2c_board_info));