Kernel driver lis3lv02d
-==================
+=======================
Supported chips:
* STMicroelectronics LIS3LV02DL and LIS3LV02DQ
-Author:
+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 detect automatically laptops with this sensor. Known models
-(for now the HP 2133, nc6420, nc2510, nc8510, nc84x0, nw9440 and nx9420) will
-have their axis automatically oriented on standard way (eg: you can directly
-play neverball). The accelerometer data is readable via
+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 (for now the HP 2133, nc6420,
+nc2510, nc8510, nc84x0, nw9440 and nx9420) 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.
Sysfs attributes under /sys/devices/platform/lis3lv02d/:
position - 3D position that the accelerometer reports. Format: "(x,y,z)"
-calibrate - read: values (x, y, z) that are used as the base for input class device operation.
- write: forces the base to be recalibrated with the current position.
+calibrate - read: values (x, y, z) that are used as the base for input
+ class device operation.
+ write: forces the base to be recalibrated with the current
+ position.
rate - reports the sampling rate of the accelerometer device in HZ
This driver also provides an absolute input class device, allowing
the laptop to act as a pinball machine-esque joystick.
+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).
+
+
Axes orientation
----------------
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
+ 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 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
-authors 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.
+If your laptop model is not recognized (cf "dmesg"), you can send an
+email to the authors 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.