Allows users who use an IDE driver for their disk to use hpfall without
having to modify the source. By default /dev/sda is used.
Suggested by Christian Thaeter in http://lkml.org/lkml/2009/3/25/505.

While we're add it, improve error message if opening /dev/freefall fails.
Signed-off-by: NFrans Pop <elendil@planet.nl>
Cc: Christian Thaeter <ct@pipapo.org>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Improve the example code to be at least useable, as in not causing
harm (as shown below). Code can still be improved further, but this
adds some basic safeguards.

1. hpfall *MUST* mlockall(MCL_CURRENT|MCL_FUTURE); itself!
Since the Program sits and waits most of the time it becomes very likely
swapped out. If it gets woken up when the laptop drops from the table
while it is swapped out it actually triggers harddrive activity!

2. Daemonize hpfall using 'daemon(0,0)' (quick and dirty).

3. Give hpfall realtime priority.
Should give a chance that it has less latency when woken up.
Signed-off-by: NChristian Thaeter <ct@pipapo.org>
Signed-off-by: NFrans Pop <elendil@planet.nl>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

This patch makes hpfall.c conform to kernel coding style.

I have not fixed the C99 // comments on two lines as they
help indicate that those are not actually comments but
incomplete code.

Before:
 total: 10 errors, 6 warnings, 101 lines checked
After:
 total: 2 errors, 0 warnings, 99 lines checked
Signed-off-by: NFrans Pop <elendil@planet.nl>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

This adds freefall handling to hp_accel driver.  According to HP, it
should just work, without us having to set the chip up by hand.

hpfall.c is example .c program that parks the disk when accelerometer
detects free fall.  It should work; for now, it uses fixed 20seconds
protection period.
Signed-off-by: NPavel Machek <pavel@suse.cz>
Cc: Thomas Renninger <trenn@suse.de>
Cc: Éric Piel <eric.piel@tremplin-utc.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>