path: root/Documentation/misc-devices/lis3lv02d.rst
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authorMauro Carvalho Chehab <>2019-06-28 18:23:13 -0300
committerGreg Kroah-Hartman <>2019-07-03 21:09:41 +0200
commit9b5db89ea4bfdbb23d4f85f3a7fbf2cd36d20146 (patch)
tree94d68f0a652ab381412336b968ef36094c182973 /Documentation/misc-devices/lis3lv02d.rst
parent69416739ee3692f4ba890f153d9000e865b73c2d (diff)
docs: misc-devices: convert files without extension to ReST
Those files are also text files. Convert them to ReST and add to the misc-files index.rst. Signed-off-by: Mauro Carvalho Chehab <> Link: Signed-off-by: Greg Kroah-Hartman <>
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+Kernel driver lis3lv02d
+Supported chips:
+ * STMicroelectronics LIS3LV02DL, LIS3LV02DQ (12 bits precision)
+ * STMicroelectronics LIS302DL, LIS3L02DQ, LIS331DL (8 bits) and
+ LIS331DLH (16 bits)
+ - Yan Burman <>
+ - Eric Piel <>
+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/:
+ - 3D position that the accelerometer reports. Format: "(x,y,z)"
+ - 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.
+ - 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: 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.