Re: select() on /dev/input/eventX not level-triggered?

[Pavel Machek <pavel@ucw.cz>]

On Mon 2011-05-23 11:13:12, Dmitry Torokhov wrote:
> On Fri, May 20, 2011 at 01:50:51AM +0200, Pavel Machek wrote:
> > Hi!
> > 
> > I'm debugging strange behaviour on /dev/input/eventX ... it seems that
> > select is not behaving level-triggered as it apparently should. I can
> > reproduce it when hitting windows & alt keys.
> > 
> > Now, I really should rewrite it into C, first, but perhaps someone has
> > an idea?

(Ok, so  we agree that select()  should mark descriptor as ready as
long as data are available... right?)

> Is this with next or with mainline? In next we try not to signal that FD
> is ready unless we have full packet in the buffer...

2.6.39-rcX mainline.

> FWIW I see python indeed not reading the tail of events (btw the format
> should be 'llhhi' and the size on 64 bit arches is 24, not 16) but when
> I hacked evtest to use select and non-blockign read it all worked
> properly.

It  was on x32, but I'll fix that, thanks.

Difference was I'm not using non-blocking read(). It is unusual but
should work AFAICT. Just read one packet when select shows its ready;
if there's more than one, don't loop around read, but rely on select
returning immediately.

I did verify it on strace, so it should not  be python artefact.
								Pavel
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