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-Kernel driver lis3lv02d
-=======================
-
-Supported chips:
-
- * STMicroelectronics LIS3LV02DL, LIS3LV02DQ (12 bits precision)
- * STMicroelectronics LIS302DL, LIS3L02DQ, LIS331DL (8 bits)
-
-Authors:
- Yan Burman <burman.yan@gmail.com>
- Eric Piel <eric.piel@tremplin-utc.net>
-
-
-Description
------------
-
-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).
-
-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.
-
-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.
-
-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.
-
-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.
-
-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 hpfall.c
-file for an example on using the device.
-
-
-Axes orientation
-----------------
-
-For better compatibility between the various laptops. The values reported by
-the accelerometer are converted into a "standard" organisation of the axes
-(aka "can play neverball out of the box"):
- * When the laptop is horizontal the position reported is about 0 for X and Y
- and a positive value for Z
- * If the left side is elevated, X increases (becomes positive)
- * If the front side (where the touchpad is) is elevated, Y decreases
- (becomes negative)
- * If the laptop is put upside-down, Z becomes negative
-
-If your laptop model is not recognized (cf "dmesg"), you can send an
-email to the maintainer to add it to the database. When reporting a new
-laptop, please include the output of "dmidecode" plus the value of
-/sys/devices/platform/lis3lv02d/position in these four cases.
-
-Q&A
----
-
-Q: How do I safely simulate freefall? I have an HP "portable
-workstation" which has about 3.5kg and a plastic case, so letting it
-fall to the ground is out of question...
-
-A: The sensor is pretty sensitive, so your hands can do it. Lift it
-into free space, follow the fall with your hands for like 10
-centimeters. That should be enough to trigger the detection.