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1=======================2Kernel driver lis3lv02d3=======================4 5Supported chips:6 7 * STMicroelectronics LIS3LV02DL, LIS3LV02DQ (12 bits precision)8 * STMicroelectronics LIS302DL, LIS3L02DQ, LIS331DL (8 bits) and9 LIS331DLH (16 bits)10 11Authors:12 - Yan Burman <burman.yan@gmail.com>13 - Eric Piel <eric.piel@tremplin-utc.net>14 15 16Description17-----------18 19This driver provides support for the accelerometer found in various HP laptops20sporting the feature officially called "HP Mobile Data Protection System 3D" or21"HP 3D DriveGuard". It detects automatically laptops with this sensor. Known22models (full list can be found in drivers/platform/x86/hp_accel.c) will have23their axis automatically oriented on standard way (eg: you can directly play24neverball). The accelerometer data is readable via25/sys/devices/platform/lis3lv02d. Reported values are scaled26to mg values (1/1000th of earth gravity).27 28Sysfs attributes under /sys/devices/platform/lis3lv02d/:29 30position31 - 3D position that the accelerometer reports. Format: "(x,y,z)"32rate33 - read reports the sampling rate of the accelerometer device in HZ.34 write changes sampling rate of the accelerometer device.35 Only values which are supported by HW are accepted.36selftest37 - performs selftest for the chip as specified by chip manufacturer.38 39This driver also provides an absolute input class device, allowing40the laptop to act as a pinball machine-esque joystick. Joystick device can be41calibrated. Joystick device can be in two different modes.42By default output values are scaled between -32768 .. 32767. In joystick raw43mode, joystick and sysfs position entry have the same scale. There can be44small difference due to input system fuzziness feature.45Events are also available as input event device.46 47Selftest is meant only for hardware diagnostic purposes. It is not meant to be48used during normal operations. Position data is not corrupted during selftest49but interrupt behaviour is not guaranteed to work reliably. In test mode, the50sensing element is internally moved little bit. Selftest measures difference51between normal mode and test mode. Chip specifications tell the acceptance52limit for each type of the chip. Limits are provided via platform data53to allow adjustment of the limits without a change to the actual driver.54Seltest returns either "OK x y z" or "FAIL x y z" where x, y and z are55measured difference between modes. Axes are not remapped in selftest mode.56Measurement values are provided to help HW diagnostic applications to make57final decision.58 59On HP laptops, if the led infrastructure is activated, support for a led60indicating disk protection will be provided as /sys/class/leds/hp::hddprotect.61 62Another feature of the driver is misc device called "freefall" that63acts similar to /dev/rtc and reacts on free-fall interrupts received64from the device. It supports blocking operations, poll/select and65fasync operation modes. You must read 1 bytes from the device. The66result is number of free-fall interrupts since the last successful67read (or 255 if number of interrupts would not fit). See the freefall.c68file for an example on using the device.69 70 71Axes orientation72----------------73 74For better compatibility between the various laptops. The values reported by75the accelerometer are converted into a "standard" organisation of the axes76(aka "can play neverball out of the box"):77 78 * When the laptop is horizontal the position reported is about 0 for X and Y79 and a positive value for Z80 * If the left side is elevated, X increases (becomes positive)81 * If the front side (where the touchpad is) is elevated, Y decreases82 (becomes negative)83 * If the laptop is put upside-down, Z becomes negative84 85If your laptop model is not recognized (cf "dmesg"), you can send an86email to the maintainer to add it to the database. When reporting a new87laptop, please include the output of "dmidecode" plus the value of88/sys/devices/platform/lis3lv02d/position in these four cases.89 90Q&A91---92 93Q: How do I safely simulate freefall? I have an HP "portable94workstation" which has about 3.5kg and a plastic case, so letting it95fall to the ground is out of question...96 97A: The sensor is pretty sensitive, so your hands can do it. Lift it98into free space, follow the fall with your hands for like 1099centimeters. That should be enough to trigger the detection.100