1 ======================= 2 Kernel driver lis3lv02d 3 ======================= 4 5 Supported chips: 6 7 * STMicroelectronics LIS3LV02DL, LIS3LV02DQ (12 bits precision) 8 * STMicroelectronics LIS302DL, LIS3L02DQ, LIS331DL (8 bits) and 9 LIS331DLH (16 bits) 10 11 Authors: 12 - Yan Burman <burman.yan@gmail.com> 13 - Eric Piel <eric.piel@tremplin-utc.net> 14 15 16 Description 17 ----------- 18 19 This driver provides support for the accelerometer found in various HP laptops 20 sporting the feature officially called "HP Mobile Data Protection System 3D" or 21 "HP 3D DriveGuard". It detects automatically laptops with this sensor. Known 22 models (full list can be found in drivers/platform/x86/hp_accel.c) will have 23 their axis automatically oriented on standard way (eg: you can directly play 24 neverball). The accelerometer data is readable via 25 /sys/devices/platform/lis3lv02d. Reported values are scaled 26 to mg values (1/1000th of earth gravity). 27 28 Sysfs attributes under /sys/devices/platform/lis3lv02d/: 29 30 position 31 - 3D position that the accelerometer reports. Format: "(x,y,z)" 32 rate 33 - 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. 36 selftest 37 - performs selftest for the chip as specified by chip manufacturer. 38 39 This driver also provides an absolute input class device, allowing 40 the laptop to act as a pinball machine-esque joystick. Joystick device can be 41 calibrated. Joystick device can be in two different modes. 42 By default output values are scaled between -32768 .. 32767. In joystick raw 43 mode, joystick and sysfs position entry have the same scale. There can be 44 small difference due to input system fuzziness feature. 45 Events are also available as input event device. 46 47 Selftest is meant only for hardware diagnostic purposes. It is not meant to be 48 used during normal operations. Position data is not corrupted during selftest 49 but interrupt behaviour is not guaranteed to work reliably. In test mode, the 50 sensing element is internally moved little bit. Selftest measures difference 51 between normal mode and test mode. Chip specifications tell the acceptance 52 limit for each type of the chip. Limits are provided via platform data 53 to allow adjustment of the limits without a change to the actual driver. 54 Seltest returns either "OK x y z" or "FAIL x y z" where x, y and z are 55 measured difference between modes. Axes are not remapped in selftest mode. 56 Measurement values are provided to help HW diagnostic applications to make 57 final decision. 58 59 On HP laptops, if the led infrastructure is activated, support for a led 60 indicating disk protection will be provided as /sys/class/leds/hp::hddprotect. 61 62 Another feature of the driver is misc device called "freefall" that 63 acts similar to /dev/rtc and reacts on free-fall interrupts received 64 from the device. It supports blocking operations, poll/select and 65 fasync operation modes. You must read 1 bytes from the device. The 66 result is number of free-fall interrupts since the last successful 67 read (or 255 if number of interrupts would not fit). See the freefall.c 68 file for an example on using the device. 69 70 71 Axes orientation 72 ---------------- 73 74 For better compatibility between the various laptops. The values reported by 75 the accelerometer are converted into a "standard" organisation of the axes 76 (aka "can play neverball out of the box"): 77 78 * When the laptop is horizontal the position reported is about 0 for X and Y 79 and a positive value for Z 80 * If the left side is elevated, X increases (becomes positive) 81 * If the front side (where the touchpad is) is elevated, Y decreases 82 (becomes negative) 83 * If the laptop is put upside-down, Z becomes negative 84 85 If your laptop model is not recognized (cf "dmesg"), you can send an 86 email to the maintainer to add it to the database. When reporting a new 87 laptop, please include the output of "dmidecode" plus the value of 88 /sys/devices/platform/lis3lv02d/position in these four cases. 89 90 Q&A 91 --- 92 93 Q: How do I safely simulate freefall? I have an HP "portable 94 workstation" which has about 3.5kg and a plastic case, so letting it 95 fall to the ground is out of question... 96 97 A: The sensor is pretty sensitive, so your hands can do it. Lift it 98 into free space, follow the fall with your hands for like 10 99 centimeters. That should be enough to trigger the detection.
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