[maemo-developers] Instructions cache flush on ARM (was: N800 & Video playback)

[From: Guillem Jover]

On Mon, 2007-04-23 at 21:09:26 +0300, ext Siarhei Siamashka wrote:
> On Monday 23 April 2007 16:49, Guillem Jover wrote:
> > > You are right. gcc has function
> > > void __clear_cache (char *BEG, char *END)
> > > which should be more portable.
> >
> > It should, but it still has the problem of emitting an OABI syscall
> > due to our old gcc.
> >
> > You could use syscall(2) and __ARM_NR_cacheflush instead.
> 
> Yes, but __clear_cache(char *BEG, char *END)  works fine with the 
> current combination of gcc and kernel in maemo. So I guess it's the best 
> option if portability is desired.

That it works fine now does not mean it's the correct solution. Also I
disagree on the premise that it's more portable, both solutions are
quite non-portable, either you'll have to check if that function is
present in autoconf or similar, or you'll have to check for the presence
of the syscall NR on arm.

> If you decide to drop support for old ABI from kernel without upgrading
> gcc, that would be a bug in maemo platform :-)

No, because as this is coming from gcc it gets embedded in the actual
object, so it would need a recompilation, I wouldn't say that's a bug
in maemo, you have hardcoded OABI calls in your object files.

Also that makes it more difficult for people to flash their own new
kernel.

regards,
guillem