60 lines
1.5 KiB
ReStructuredText
60 lines
1.5 KiB
ReStructuredText
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====================
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Kernel driver lp3944
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====================
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* National Semiconductor LP3944 Fun-light Chip
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Prefix: 'lp3944'
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Addresses scanned: None (see the Notes section below)
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Datasheet:
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Publicly available at the National Semiconductor website
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http://www.national.com/pf/LP/LP3944.html
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Authors:
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Antonio Ospite <ospite@studenti.unina.it>
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Description
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-----------
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The LP3944 is a helper chip that can drive up to 8 leds, with two programmable
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DIM modes; it could even be used as a gpio expander but this driver assumes it
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is used as a led controller.
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The DIM modes are used to set _blink_ patterns for leds, the pattern is
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specified supplying two parameters:
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- period:
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from 0s to 1.6s
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- duty cycle:
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percentage of the period the led is on, from 0 to 100
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Setting a led in DIM0 or DIM1 mode makes it blink according to the pattern.
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See the datasheet for details.
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LP3944 can be found on Motorola A910 smartphone, where it drives the rgb
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leds, the camera flash light and the lcds power.
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Notes
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-----
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The chip is used mainly in embedded contexts, so this driver expects it is
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registered using the i2c_board_info mechanism.
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To register the chip at address 0x60 on adapter 0, set the platform data
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according to include/linux/leds-lp3944.h, set the i2c board info::
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static struct i2c_board_info a910_i2c_board_info[] __initdata = {
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{
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I2C_BOARD_INFO("lp3944", 0x60),
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.platform_data = &a910_lp3944_leds,
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},
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};
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and register it in the platform init function::
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i2c_register_board_info(0, a910_i2c_board_info,
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ARRAY_SIZE(a910_i2c_board_info));
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