HDAPS
Contents
HDAPS - IBM Active Protection System Linux Driver
This is the Linux driver for monitoring the accelerometer known as IBM Active Protection System.
The driver only enables reading of the acceleration data. It does not perform automatic disk head parking. But there are already some other useful applications for HDAPS, using the /sys interface it provides.
Features
Project Homepage / Availability
Status
A driver is included in recent Linux kernels and is actively maintained, but it is very inferior to the driver in tp_smapi (which provides its own hdaps module).
How to install the driver
Recent Linux kernels include the hdaps driver. However, the driver in the mainline Linux kernel has two problems with recent models:
To solve both problems, install the modified hdaps that is bundled with tp_smapi.
Harddisk Protection
As mentioned above, the hdaps kernel driver is only responsible for reading the accelerometer data and exporting it through the sysfs interface. In order to use this information to protect the disk, some additional steps are required.
See How to protect the harddisk through APS.
Input device support
In more recent versions of the Linux kernel,bVy6hxT the hdaps exports event devices with the accelerometer data. These devices can be used as-is by some programs (e.g. hdapsd), but for most they must be handled by the additional kernel module joydev.
When both modules are loaded, joydev will provide standard joystick device emulation for hdaps (standard hdaps exports just one joystick device. enhanced hdaps from tp_smapi will export two due to issues still unsolved on joydev, but the second one must not be used as a joystick).
Udev can be used to create device nodes in /dev for use by user space programs that access the joystick, and to set appropriate permissions.
In order for non-root users to access these device files, their permissions must be tweaked a little through an appropriate udev rule and corresponding "joy" group.
# addgroup joy
# adduser <you> joy
# echo 'SUBSYSTEM=="input", KERNEL=="js*", MODE="0660", GROUP="joy"' >> /etc/udev/hdaps-joy.rules
# ln -s ../hdaps-joy.rules /etc/udev/rules.d/z60_hdaps-joy.rules
Programs you can use to test and calibrate the device files include jscalibrator (gui) and jstest/jscal (cli) packaged together (at least in Debian) simply as "joystick".
Applications
Disk head parking
You will need the kernel patch below and the hdapsd userspace daemon. The GUI monitoring is optional.
See How to protect the harddisk through APS for more information.
Kernel patch
Due to significant changes in the way the libata module which handles disk i/o, applying any of the currently available patches to kernel 2.6.24 will intermittently cause system hangs when the queue is frozen (i.e., the heads are parked). It is recommended either that you stay at kernel 2.6.23 or do without disk protection in 2.6.24 until the kinks have been worked out. There has been significant work on the part of Elias Oltmanns, author of the more recent patches, to get this worked out and eventually get shock protection built into the mainline kernel.
Below are some links to patches for various Linux kernel versions. As noted above, your mileage may vary with the 2.6.24-rc3 patch as it was after this release candidate that things stopped working nicely.
patch -p1 -l < hdaps_xx.patchUserspace daemon
This version optionally reduces timer interrupts (as measured by PowerTOP), and thereby reduces power consumption on modern ("tickless") Linux kernels. Interrupt reduction requires the hdaps kernel module from tp_smapi 0.32 or newer, and a udev rule. If these are not present, it will default to an older polling method that is slightly more power-hungry. The udev rule helps hdapsd find the input device, and on most distributions it can be created as follows:
# echo 'KERNEL=="event[0-9]*", ATTRS{phys}=="hdaps/input1",ATTRS{modalias}=="input:b0019v1014p5054e4801-*",SYMLINK+="input/hdaps/accelerometer-event"' \
> /etc/udev/rules.d/51-hdaps.rules
Then reboot or run # /sbin/udevtrigger, and verify that the /dev/input/hdaps/accelerometer-event symlink exists.
Use an overlay listed bellow with updated versions of related packages
