Am Freitag, 30. März 2007 17:41 schrieb Greg KH:
> On Fri, Mar 30, 2007 at 11:17:28AM +0200, Oliver Neukum wrote:
> > However it would not always work out so nicely.
> > Have a look at this code from usblp:
> >
> > timeout = USBLP_WRITE_TIMEOUT;
> >
> > rv = wait_event_interruptible_timeout(usblp->wait,
> > usblp->wcomplete || !usblp->present , timeout);
> > if (rv < 0)
> > return writecount ? writecount : -EINTR;
>
> Well, usblp incorrectly (in my opinion) tries to return the status of
> every urb to userspace. I'm still not quite sure why it needs to do
> that, and we can't just throw a ton of urbs at the device and then walk
> away. It's not like userspace does much if we report an error on the
> exact packet that fails, vs a packet later on, right?
I can't tell you whether cups closes the device for every job.
But it does not matter. Keeping it open is fully legitimate. You must
know which urb has failed to know whose print job has failed.
[..]
> I think it really comes down to the problem of checking the urb status
> flag.
Only for the write case. Reading needs the transfer_buffer.
mdc800 has exactly that race. You are looking for a work around now.
> I _REALLY_ want to get rid of that field and not have drivers us it at
> all. I would like to pass the value of the status flag to the urb
> callback directly, and only have the status field be used by the host
> controllers.
Good idea in any case.
> The last time I looked into implementing this, I think the UHCI driver
> had some 'issues' with how it would work, or maybe it was EHCI, sorry it
> was a few years ago.
>
> However, if we are able to fix that, and never let drivers touch that
> field, then the large majority of these kinds of problems will go away,
> right?
I haven't counted them. I guess it is safe to say that many issues
would go away.
Regards
Oliver
-------------------------------------------------------------------------
Take Surveys. Earn Cash. Influence the Future of IT
Join SourceForge.net's Techsay panel and you'll get the chance to share your
opinions on IT & business topics through brief surveys-and earn cash
http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
_______________________________________________
linux-usb-devel@lists.sourceforge.net
To unsubscribe, use the last form field at:
https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
