Re: correctly handling EPROTO

[Michal Pecio <michal.pecio@gmail.com>]

On Sat, 21 Mar 2026 11:58:53 -0400, Alan Stern wrote:
> On Sat, Mar 21, 2026 at 06:54:24AM +0100, Michal Pecio wrote:
> > Nope, for many years now, if not forever, xhci-hcd has been
> > restarting the endpoint after giving back the failed URB if its
> > completion hasn't unlinked all remaining URBs.  
> 
> How can that work in the presence of BH givebacks?

Certainly not reliably and I started a similar thread two years ago
after coming to this exact realization.

Does anyone know class drivers affected by this which could be used
to validate such changes? Writing a patch is one thing, knowing whether
it does any good is another. I recall that last time Mathias tried to
touch this logic it caused a regression by unearthing more issues.

I was reluctant to touch this mess in absence of known impact. The race
is as old as BH giveback (2019) and automatic restarting is even older.
It could get awkward if users (or driver developers) learned to expect
this behavior.

But if somebody can point out serious issues like data loss in storage
then it's a different ball game.

Regards,
Michal