0024d6e9fd
hpfall.c was renamed to freefall.c in 3.16, but this file still refer to hpfall.c instead of freefall.c Signed-off-by: Masanari Iida <standby24x7@gmail.com> Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
93 lines
4.2 KiB
Text
93 lines
4.2 KiB
Text
Kernel driver lis3lv02d
|
|
=======================
|
|
|
|
Supported chips:
|
|
|
|
* STMicroelectronics LIS3LV02DL, LIS3LV02DQ (12 bits precision)
|
|
* STMicroelectronics LIS302DL, LIS3L02DQ, LIS331DL (8 bits) and
|
|
LIS331DLH (16 bits)
|
|
|
|
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 (full list can be found in drivers/platform/x86/hp_accel.c) 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. Reported values are scaled
|
|
to mg values (1/1000th of earth gravity).
|
|
|
|
Sysfs attributes under /sys/devices/platform/lis3lv02d/:
|
|
position - 3D position that the accelerometer reports. Format: "(x,y,z)"
|
|
rate - read reports the sampling rate of the accelerometer device in HZ.
|
|
write changes sampling rate of the accelerometer device.
|
|
Only values which are supported by HW are accepted.
|
|
selftest - performs selftest for the chip as specified by chip manufacturer.
|
|
|
|
This driver also provides an absolute input class device, allowing
|
|
the laptop to act as a pinball machine-esque joystick. Joystick device can be
|
|
calibrated. Joystick device can be in two different modes.
|
|
By default output values are scaled between -32768 .. 32767. In joystick raw
|
|
mode, joystick and sysfs position entry have the same scale. There can be
|
|
small difference due to input system fuzziness feature.
|
|
Events are also available as input event device.
|
|
|
|
Selftest is meant only for hardware diagnostic purposes. It is not meant to be
|
|
used during normal operations. Position data is not corrupted during selftest
|
|
but interrupt behaviour is not guaranteed to work reliably. In test mode, the
|
|
sensing element is internally moved little bit. Selftest measures difference
|
|
between normal mode and test mode. Chip specifications tell the acceptance
|
|
limit for each type of the chip. Limits are provided via platform data
|
|
to allow adjustment of the limits without a change to the actual driver.
|
|
Seltest returns either "OK x y z" or "FAIL x y z" where x, y and z are
|
|
measured difference between modes. Axes are not remapped in selftest mode.
|
|
Measurement values are provided to help HW diagnostic applications to make
|
|
final decision.
|
|
|
|
On HP laptops, if the led infrastructure is activated, support for a led
|
|
indicating disk protection will be provided as /sys/class/leds/hp::hddprotect.
|
|
|
|
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). See the freefall.c
|
|
file for an example on using the device.
|
|
|
|
|
|
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 maintainer 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.
|