linux-stable/Documentation/backlight/lp855x-driver.txt
Kim, Milo 7be865ab86 backlight: new backlight driver for LP855x devices
THis driver supports TI LP8550/LP8551/LP8552/LP8553/LP8556 backlight
devices.

The brightness can be controlled by the I2C or PWM input.  The lp855x
driver provides both modes.  For the PWM control, pwm-specific functions
can be defined in the platform data.  And some information can be read
via the sysfs(lp855x device attributes).

For details, please refer to Documentation/backlight/lp855x-driver.txt.

[axel.lin@gmail.com: add missing mutex_unlock in lp855x_read_byte() error path]
[axel.lin@gmail.com: check platform data in lp855x_probe()]
[axel.lin@gmail.com: small cleanups]
[dan.carpenter@oracle.com: silence a compiler warning]
[axel.lin@gmail.com: use id->driver_data to differentiate lp855x chips]
[akpm@linux-foundation.org: simplify boolean return expression]
Signed-off-by: Milo(Woogyom) Kim <milo.kim@ti.com>
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-23 16:58:33 -07:00

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2.2 KiB
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Kernel driver lp855x
====================
Backlight driver for LP855x ICs
Supported chips:
Texas Instruments LP8550, LP8551, LP8552, LP8553 and LP8556
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/lp8556
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.
* mode : Brightness control mode. PWM or register based.
* device_control : Value of DEVICE CONTROL register.
* initial_brightness : Initial value of backlight brightness.
* pwm_data : Platform specific pwm generation functions.
Only valid when brightness is pwm input mode.
Functions should be implemented by PWM driver.
- pwm_set_intensity() : set duty of PWM
- pwm_get_intensity() : get current duty of PWM
* load_new_rom_data :
0 : use default configuration data
1 : update values of eeprom or eprom registers on loading driver
* 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",
.mode = REGISTER_BASED,
.device_control = I2C_CONFIG(LP8552),
.initial_brightness = INITIAL_BRT,
.load_new_rom_data = 1,
.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 = {
.mode = PWM_BASED,
.device_control = PWM_CONFIG(LP8556),
.initial_brightness = INITIAL_BRT,
.pwm_data = {
.pwm_set_intensity = platform_pwm_set_intensity,
.pwm_get_intensity = platform_pwm_get_intensity,
},
};