netdev - Re: [PATCH] usbnet: Activate halt interrupt endpoint before re-submit URB

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Date:	Wed, 20 Jun 2012 12:21:37 +0200
From:	Oliver Neukum <oneukum@...e.de>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	Huajun Li <huajun.li.lee@...il.com>,
	David Miller <davem@...emloft.net>, stern@...land.harvard.edu,
	linux-usb@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] usbnet: Activate halt interrupt endpoint before re-submit URB

Am Mittwoch, 20. Juni 2012, 12:15:25 schrieb Ming Lei:
> On Wed, Jun 20, 2012 at 4:58 PM, Oliver Neukum <oneukum@...e.de> wrote:
> > Am Mittwoch, 20. Juni 2012, 10:07:55 schrieb Ming Lei:
> >> BTW, maybe it is better to add below
> >>
> >>     usbnet_defer_kevent(dev, EVENT_STS_HALT);
> >>
> >> for -EPIPE returned from usb_urb_submit if it will be resent.
> >
> > Why? If it failed once it'll probably also fail the next time.
> 
> -EPIPE just means the endpoint is halted, either from usb_urb_submit
> or urb->status, so the HALT should be cleared in the situation.

It probably was halted and cleared. However that you cleared
a halt doesn't mean that the reason for stalling went away.
So you must cope with an endpoint being halted again right after
it was cleared.

> > In that case we'd need to do something more intrusive
> > like resetting the device, but that cannot be done well
> > in the generic usbnet part.
> 
> IMO, resetting is not needed for -EPIPE, but may be needed for
> -EPROTO failure.

We don't need it for a single failure, but what else would we do
if we keep getting -EPIPE?

	Regards
		Oliver

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