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author | Jean Delvare <khali@linux-fr.org> | 2011-03-21 17:59:36 +0100 |
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committer | Jean Delvare <khali@endymion.delvare> | 2011-03-21 17:59:36 +0100 |
commit | ff606677f6a47c63329cf8e6c7cf978c29f2d736 (patch) | |
tree | 565bcdaa1f5058af0a6fd2260b3c45029c955d08 /Documentation/misc-devices/lis3lv02d | |
parent | efcfed9bad88be8193ee6a1b8e72d7381e7b0e0e (diff) | |
download | linux-ff606677f6a47c63329cf8e6c7cf978c29f2d736.tar.bz2 |
Move lis3lv02d drivers to drivers/misc
The lis3lv02d drivers aren't hardware monitoring drivers, so the don't
belong to drivers/hwmon. Move them to drivers/misc, short of a better
home.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>
Acked-by: Eric Piel <eric.piel@tremplin-utc.net>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Tested-by: Eric Piel <eric.piel@tremplin-utc.net>
Tested-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'Documentation/misc-devices/lis3lv02d')
-rw-r--r-- | Documentation/misc-devices/lis3lv02d | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/Documentation/misc-devices/lis3lv02d b/Documentation/misc-devices/lis3lv02d new file mode 100644 index 000000000000..f1a4ec840f86 --- /dev/null +++ b/Documentation/misc-devices/lis3lv02d @@ -0,0 +1,92 @@ +Kernel driver lis3lv02d +======================= + +Supported chips: + + * STMicroelectronics LIS3LV02DL, LIS3LV02DQ (12 bits precision) + * STMicroelectronics LIS302DL, LIS3L02DQ, LIS331DL (8 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 hpfall.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. |