projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 455fbdd3 | 1 | Kernel driver lis3lv02d |
| 2b872903 | 2 | ======================= |
| 455fbdd3 PM |
3 | |
| 4 | Supported chips: | |
| 5 | ||
| 6 | * STMicroelectronics LIS3LV02DL and LIS3LV02DQ | |
| 7 | ||
| 2b872903 | 8 | Authors: |
| 455fbdd3 PM |
9 | Yan Burman <burman.yan@gmail.com> |
| 10 | Eric Piel <eric.piel@tremplin-utc.net> | |
| 11 | ||
| 12 | ||
| 13 | Description | |
| 14 | ----------- | |
| 15 | ||
| 219beb29 PM |
16 | This driver provides support for the accelerometer found in various HP |
| 17 | laptops sporting the feature officially called "HP Mobile Data | |
| 2b872903 | 18 | Protection System 3D" or "HP 3D DriveGuard". It detects automatically |
| 219beb29 PM |
19 | laptops with this sensor. Known models (for now the HP 2133, nc6420, |
| 20 | nc2510, nc8510, nc84x0, nw9440 and nx9420) will have their axis | |
| 21 | automatically oriented on standard way (eg: you can directly play | |
| 22 | neverball). The accelerometer data is readable via | |
| 455fbdd3 PM |
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)" | |
| 219beb29 PM |
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. |
| 455fbdd3 PM |
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 | ||
| ef2cfc79 PM |
36 | Another feature of the driver is misc device called "freefall" that |
| 37 | acts similar to /dev/rtc and reacts on free-fall interrupts received | |
| 38 | from the device. It supports blocking operations, poll/select and | |
| 39 | fasync operation modes. You must read 1 bytes from the device. The | |
| 40 | result is number of free-fall interrupts since the last successful | |
| 41 | read (or 255 if number of interrupts would not fit). | |
| 42 | ||
| 43 | ||
| 455fbdd3 PM |
44 | Axes orientation |
| 45 | ---------------- | |
| 46 | ||
| 47 | For better compatibility between the various laptops. The values reported by | |
| 48 | the accelerometer are converted into a "standard" organisation of the axes | |
| 49 | (aka "can play neverball out of the box"): | |
| 50 | * When the laptop is horizontal the position reported is about 0 for X and Y | |
| 2b872903 | 51 | and a positive value for Z |
| 455fbdd3 | 52 | * If the left side is elevated, X increases (becomes positive) |
| 219beb29 PM |
53 | * If the front side (where the touchpad is) is elevated, Y decreases |
| 54 | (becomes negative) | |
| 455fbdd3 PM |
55 | * If the laptop is put upside-down, Z becomes negative |
| 56 | ||
| 219beb29 PM |
57 | If your laptop model is not recognized (cf "dmesg"), you can send an |
| 58 | email to the authors to add it to the database. When reporting a new | |
| 59 | laptop, please include the output of "dmidecode" plus the value of | |
| 60 | /sys/devices/platform/lis3lv02d/position in these four cases. | |
| 455fbdd3 | 61 | |
| 2b872903 PM |
62 | Q&A |
| 63 | --- | |
| 64 | ||
| 65 | Q: How do I safely simulate freefall? I have an HP "portable | |
| 66 | workstation" which has about 3.5kg and a plastic case, so letting it | |
| 67 | fall to the ground is out of question... | |
| 68 | ||
| 69 | A: The sensor is pretty sensitive, so your hands can do it. Lift it | |
| 70 | into free space, follow the fall with your hands for like 10 | |
| 71 | centimeters. That should be enough to trigger the detection. |