linux-imx

Kernel driver lis3lv02d

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Supported chips:

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  * STMicroelectronics LIS3LV02DL, LIS3LV02DQ (12 bits precision)

  * STMicroelectronics LIS302DL, LIS3L02DQ, LIS331DL (8 bits) and

    LIS331DLH (16 bits)

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Authors:

        Yan Burman <burman.yan@gmail.com>

    Eric Piel <eric.piel@tremplin-utc.net>

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Description

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This driver provides support for the accelerometer found in various HP laptops

sporting the feature officially called "HP Mobile Data Protection System 3D" or

"HP 3D DriveGuard". It detects automatically laptops with this sensor. Known

models (full list can be found in drivers/platform/x86/hp_accel.c) will have

their axis automatically oriented on standard way (eg: you can directly play

neverball). The accelerometer data is readable via

/sys/devices/platform/lis3lv02d. Reported values are scaled

to mg values (1/1000th of earth gravity).

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Sysfs attributes under /sys/devices/platform/lis3lv02d/:

position - 3D position that the accelerometer reports. Format: "(x,y,z)"

rate - read reports the sampling rate of the accelerometer device in HZ.

    write changes sampling rate of the accelerometer device.

    Only values which are supported by HW are accepted.

selftest - performs selftest for the chip as specified by chip manufacturer.

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This driver also provides an absolute input class device, allowing

the laptop to act as a pinball machine-esque joystick. Joystick device can be

calibrated. Joystick device can be in two different modes.

By default output values are scaled between -32768 .. 32767. In joystick raw

mode, joystick and sysfs position entry have the same scale. There can be

small difference due to input system fuzziness feature.

Events are also available as input event device.

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Selftest is meant only for hardware diagnostic purposes. It is not meant to be

used during normal operations. Position data is not corrupted during selftest

but interrupt behaviour is not guaranteed to work reliably. In test mode, the

sensing element is internally moved little bit. Selftest measures difference

between normal mode and test mode. Chip specifications tell the acceptance

limit for each type of the chip. Limits are provided via platform data

to allow adjustment of the limits without a change to the actual driver.

Seltest returns either "OK x y z" or "FAIL x y z" where x, y and z are

measured difference between modes. Axes are not remapped in selftest mode.

Measurement values are provided to help HW diagnostic applications to make

final decision.

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On HP laptops, if the led infrastructure is activated, support for a led

indicating disk protection will be provided as /sys/class/leds/hp::hddprotect.

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Another feature of the driver is misc device called "freefall" that

acts similar to /dev/rtc and reacts on free-fall interrupts received

from the device. It supports blocking operations, poll/select and

fasync operation modes. You must read 1 bytes from the device.  The

result is number of free-fall interrupts since the last successful

read (or 255 if number of interrupts would not fit). See the freefall.c

file for an example on using the device.