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455fbdd3 | 1 | Kernel driver lis3lv02d |
2b872903 | 2 | ======================= |
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3 | |
4 | Supported chips: | |
5 | ||
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6 | * STMicroelectronics LIS3LV02DL, LIS3LV02DQ (12 bits precision) |
7 | * STMicroelectronics LIS302DL, LIS3L02DQ, LIS331DL (8 bits) | |
455fbdd3 | 8 | |
2b872903 | 9 | Authors: |
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10 | Yan Burman <burman.yan@gmail.com> |
11 | Eric Piel <eric.piel@tremplin-utc.net> | |
12 | ||
13 | ||
14 | Description | |
15 | ----------- | |
16 | ||
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17 | This driver provides support for the accelerometer found in various HP laptops |
18 | sporting the feature officially called "HP Mobile Data Protection System 3D" or | |
19 | "HP 3D DriveGuard". It detects automatically laptops with this sensor. Known | |
20 | models (full list can be found in drivers/hwmon/hp_accel.c) will have their | |
21 | axis automatically oriented on standard way (eg: you can directly play | |
22 | neverball). The accelerometer data is readable via | |
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23 | /sys/devices/platform/lis3lv02d. |
24 | ||
25 | Sysfs attributes under /sys/devices/platform/lis3lv02d/: | |
26 | position - 3D position that the accelerometer reports. Format: "(x,y,z)" | |
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27 | calibrate - read: values (x, y, z) that are used as the base for input |
28 | class device operation. | |
29 | write: forces the base to be recalibrated with the current | |
2b872903 | 30 | position. |
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31 | rate - reports the sampling rate of the accelerometer device in HZ |
32 | ||
33 | This driver also provides an absolute input class device, allowing | |
34 | the laptop to act as a pinball machine-esque joystick. | |
35 | ||
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36 | On HP laptops, if the led infrastructure is activated, support for a led |
37 | indicating disk protection will be provided as /sys/class/leds/hp::hddprotect. | |
38 | ||
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39 | Another feature of the driver is misc device called "freefall" that |
40 | acts similar to /dev/rtc and reacts on free-fall interrupts received | |
41 | from the device. It supports blocking operations, poll/select and | |
42 | fasync operation modes. You must read 1 bytes from the device. The | |
43 | result is number of free-fall interrupts since the last successful | |
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44 | read (or 255 if number of interrupts would not fit). See the hpfall.c |
45 | file for an example on using the device. | |
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46 | |
47 | ||
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48 | Axes orientation |
49 | ---------------- | |
50 | ||
51 | For better compatibility between the various laptops. The values reported by | |
52 | the accelerometer are converted into a "standard" organisation of the axes | |
53 | (aka "can play neverball out of the box"): | |
54 | * When the laptop is horizontal the position reported is about 0 for X and Y | |
2b872903 | 55 | and a positive value for Z |
455fbdd3 | 56 | * If the left side is elevated, X increases (becomes positive) |
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57 | * If the front side (where the touchpad is) is elevated, Y decreases |
58 | (becomes negative) | |
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59 | * If the laptop is put upside-down, Z becomes negative |
60 | ||
219beb29 | 61 | If your laptop model is not recognized (cf "dmesg"), you can send an |
bc62c147 | 62 | email to the maintainer to add it to the database. When reporting a new |
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63 | laptop, please include the output of "dmidecode" plus the value of |
64 | /sys/devices/platform/lis3lv02d/position in these four cases. | |
455fbdd3 | 65 | |
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66 | Q&A |
67 | --- | |
68 | ||
69 | Q: How do I safely simulate freefall? I have an HP "portable | |
70 | workstation" which has about 3.5kg and a plastic case, so letting it | |
71 | fall to the ground is out of question... | |
72 | ||
73 | A: The sensor is pretty sensitive, so your hands can do it. Lift it | |
74 | into free space, follow the fall with your hands for like 10 | |
75 | centimeters. That should be enough to trigger the detection. |