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kernel/linux-imx6_3.14.28/Documentation/backlight/lp855x-driver.txt 1.74 KB
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  Kernel driver lp855x
  ====================
  
  Backlight driver for LP855x ICs
  
  Supported chips:
  	Texas Instruments LP8550, LP8551, LP8552, LP8553, LP8555, LP8556 and
  	LP8557
  
  Author: Milo(Woogyom) Kim <milo.kim@ti.com>
  
  Description
  -----------
  
  * Brightness control
  
  Brightness can be controlled by the pwm input or the i2c command.
  The lp855x driver supports both cases.
  
  * Device attributes
  
  1) bl_ctl_mode
  Backlight control mode.
  Value : pwm based or register based
  
  2) chip_id
  The lp855x chip id.
  Value : lp8550/lp8551/lp8552/lp8553/lp8555/lp8556/lp8557
  
  Platform data for lp855x
  ------------------------
  
  For supporting platform specific data, the lp855x platform data can be used.
  
  * name : Backlight driver name. If it is not defined, default name is set.
  * device_control : Value of DEVICE CONTROL register.
  * initial_brightness : Initial value of backlight brightness.
  * period_ns : Platform specific PWM period value. unit is nano.
  	     Only valid when brightness is pwm input mode.
  * size_program : Total size of lp855x_rom_data.
  * rom_data : List of new eeprom/eprom registers.
  
  example 1) lp8552 platform data : i2c register mode with new eeprom data
  
  #define EEPROM_A5_ADDR	0xA5
  #define EEPROM_A5_VAL	0x4f	/* EN_VSYNC=0 */
  
  static struct lp855x_rom_data lp8552_eeprom_arr[] = {
  	{EEPROM_A5_ADDR, EEPROM_A5_VAL},
  };
  
  static struct lp855x_platform_data lp8552_pdata = {
  	.name = "lcd-bl",
  	.device_control = I2C_CONFIG(LP8552),
  	.initial_brightness = INITIAL_BRT,
  	.size_program = ARRAY_SIZE(lp8552_eeprom_arr),
  	.rom_data = lp8552_eeprom_arr,
  };
  
  example 2) lp8556 platform data : pwm input mode with default rom data
  
  static struct lp855x_platform_data lp8556_pdata = {
  	.device_control = PWM_CONFIG(LP8556),
  	.initial_brightness = INITIAL_BRT,
  	.period_ns = 1000000,
  };