Re: [patch] IBM HDAPS accelerometer driver.

[Oliver Neukum <neukum@fachschaft.cup.uni-muenchen.de>]

On Mon, 29 Aug 2005, Pavel Machek wrote:

> Hi!
> 
> > >>I think he doesn't need to export it at all and he should write code to
> > >>park and disable hard disk instead.
> > >>(in userspace it's unsolvable --- i.e. you can't enable hard disk when
> > >>detected stable condition if the daemon is swapped out on that hard disk)
> > >
> > >man mlockall() :-).
> > 
> > You also must not use any syscall that allocates even temporary memory in 
> > kernel (select, poll, many others ...) or that waits on semaphore that 
> > might be held while allocating memory (i.e. audit and rewrite ide ioctl 
> > path).
> 
> Kernel module would have exactly same problem.

It has control of its memory allocations.
 
> > And you need extra flags to protect the daemon from being killed at 
> > shutdown or blocked at suspend.
> 
> Why?

Because the disk must be unlocked even if the laptop falls down while
a suspension or shutdown are under way.
And it should work until the heads are parked anyway.

	Regards
		Oliver

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