Re: [patch] IBM HDAPS accelerometer driver.

[Pavel Machek <pavel@suse.cz>]

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.

> And you need extra flags to protect the daemon from being killed at 
> shutdown or blocked at suspend.

Why?

> >Accelerometer is usefull for other stuff besides parking heads, like
> >playing marble madness or what is the name of the game, and even
> >parking heads is way too complex to be put into the kernel.
> >
> >Even if you don't like mlockall(), you can put timeout into
> >disk-freezing interface.
> 
> That makes the protection less reliable (you shake the notebook and after 
> the timeout drop it).

Idea is that userland app keeps saying "unfreeze 5 seconds in future"
as long as you keep shaking -- essentialy a deadlock prevention.
								Pavel
-- 
if you have sharp zaurus hardware you don't need... you know my address