Based on kernel version 3.16. Page generated on 2014-08-06 21:40 EST.
1 Kernel driver lis3lv02d 2 ======================= 3 4 Supported chips: 5 6 * STMicroelectronics LIS3LV02DL, LIS3LV02DQ (12 bits precision) 7 * STMicroelectronics LIS302DL, LIS3L02DQ, LIS331DL (8 bits) and 8 LIS331DLH (16 bits) 9 10 Authors: 11 Yan Burman <firstname.lastname@example.org> 12 Eric Piel <email@example.com> 13 14 15 Description 16 ----------- 17 18 This driver provides support for the accelerometer found in various HP laptops 19 sporting the feature officially called "HP Mobile Data Protection System 3D" or 20 "HP 3D DriveGuard". It detects automatically laptops with this sensor. Known 21 models (full list can be found in drivers/platform/x86/hp_accel.c) will have 22 their axis automatically oriented on standard way (eg: you can directly play 23 neverball). The accelerometer data is readable via 24 /sys/devices/platform/lis3lv02d. Reported values are scaled 25 to mg values (1/1000th of earth gravity). 26 27 Sysfs attributes under /sys/devices/platform/lis3lv02d/: 28 position - 3D position that the accelerometer reports. Format: "(x,y,z)" 29 rate - read reports the sampling rate of the accelerometer device in HZ. 30 write changes sampling rate of the accelerometer device. 31 Only values which are supported by HW are accepted. 32 selftest - performs selftest for the chip as specified by chip manufacturer. 33 34 This driver also provides an absolute input class device, allowing 35 the laptop to act as a pinball machine-esque joystick. Joystick device can be 36 calibrated. Joystick device can be in two different modes. 37 By default output values are scaled between -32768 .. 32767. In joystick raw 38 mode, joystick and sysfs position entry have the same scale. There can be 39 small difference due to input system fuzziness feature. 40 Events are also available as input event device. 41 42 Selftest is meant only for hardware diagnostic purposes. It is not meant to be 43 used during normal operations. Position data is not corrupted during selftest 44 but interrupt behaviour is not guaranteed to work reliably. In test mode, the 45 sensing element is internally moved little bit. Selftest measures difference 46 between normal mode and test mode. Chip specifications tell the acceptance 47 limit for each type of the chip. Limits are provided via platform data 48 to allow adjustment of the limits without a change to the actual driver. 49 Seltest returns either "OK x y z" or "FAIL x y z" where x, y and z are 50 measured difference between modes. Axes are not remapped in selftest mode. 51 Measurement values are provided to help HW diagnostic applications to make 52 final decision. 53 54 On HP laptops, if the led infrastructure is activated, support for a led 55 indicating disk protection will be provided as /sys/class/leds/hp::hddprotect. 56 57 Another feature of the driver is misc device called "freefall" that 58 acts similar to /dev/rtc and reacts on free-fall interrupts received 59 from the device. It supports blocking operations, poll/select and 60 fasync operation modes. You must read 1 bytes from the device. The 61 result is number of free-fall interrupts since the last successful 62 read (or 255 if number of interrupts would not fit). See the hpfall.c 63 file for an example on using the device. 64 65 66 Axes orientation 67 ---------------- 68 69 For better compatibility between the various laptops. The values reported by 70 the accelerometer are converted into a "standard" organisation of the axes 71 (aka "can play neverball out of the box"): 72 * When the laptop is horizontal the position reported is about 0 for X and Y 73 and a positive value for Z 74 * If the left side is elevated, X increases (becomes positive) 75 * If the front side (where the touchpad is) is elevated, Y decreases 76 (becomes negative) 77 * If the laptop is put upside-down, Z becomes negative 78 79 If your laptop model is not recognized (cf "dmesg"), you can send an 80 email to the maintainer to add it to the database. When reporting a new 81 laptop, please include the output of "dmidecode" plus the value of 82 /sys/devices/platform/lis3lv02d/position in these four cases. 83 84 Q&A 85 --- 86 87 Q: How do I safely simulate freefall? I have an HP "portable 88 workstation" which has about 3.5kg and a plastic case, so letting it 89 fall to the ground is out of question... 90 91 A: The sensor is pretty sensitive, so your hands can do it. Lift it 92 into free space, follow the fall with your hands for like 10 93 centimeters. That should be enough to trigger the detection.