Kernel driver lis3lv02d ======================= Supported chips: * STMicroelectronics LIS3LV02DL and LIS3LV02DQ 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 (for now the HP 2133, nc6420, nc2510, nc8510, nc84x0, nw9440 and nx9420) 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. Sysfs attributes under /sys/devices/platform/lis3lv02d/: position - 3D position that the accelerometer reports. Format: "(x,y,z)" calibrate - read: values (x, y, z) that are used as the base for input class device operation. write: forces the base to be recalibrated with the current position. rate - reports the sampling rate of the accelerometer device in HZ This driver also provides an absolute input class device, allowing the laptop to act as a pinball machine-esque joystick. 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). 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 authors 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.