netdev - Re: [PATCH 1/2] usbnet: allow status interrupt URB to always be active

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Message-ID: <1357349193.19684.3.camel@dcbw.foobar.com>
Date:	Fri, 04 Jan 2013 19:26:33 -0600
From:	Dan Williams <dcbw@...hat.com>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	Elina Pasheva <epasheva@...rrawireless.com>,
	netdev@...r.kernel.org, linux-usb@...r.kernel.org,
	Rory Filer <rfiler@...rrawireless.com>,
	Phil Sutter <phil@....cc>
Subject: Re: [PATCH 1/2] usbnet: allow status interrupt URB to always be
 active

On Fri, 2013-01-04 at 23:16 +0100, Oliver Neukum wrote:
> On Friday 04 January 2013 10:48:16 Dan Williams wrote:
> > Some drivers (ex sierra_net) need the status interrupt URB
> > active even when the device is closed, because they receive
> > custom indications from firmware.  Allow sub-drivers to set
> > a flag that submits the status interrupt URB on probe and
> > keeps the URB alive over device open/close.  The URB is still
> > killed/re-submitted for suspend/resume, as before.
> > 
> > Signed-off-by: Dan Williams <dcbw@...hat.com>
> > ---
> > Oliver: alternatively, is there a problem with *always*
> > submitting the interrupt URB, and then simply not calling
> > the subdriver's .status function when the netdev is
> > closed?  That would be a much simpler patch.
> 
> That is quite radical. We have no idea what a device
> does when we do not react to a status update. I would
> much prefer to not take the risk.
> Besides, we don't use bandwidth if we don't have to.

Ok, so scratch the alternative.  Thus, does the posted patch look like
the right course of action?

If I wasn't clear enough before, sierra_net needs to listen to the
status interrupt URB to receive the custom Restart indication as part of
the driver's device setup.  Thus for sierra_net at least, tying the
status interrupt URB submission to device open/close isn't right.

I'd previously done a patch to handle this all in sierra_net, but the
problem there is suspend/resume: without directly accessing the usbnet
structure's ->suspend_count member (icky!) sierra_net can't correctly
kill/submit the URB itself.  So I went with a flag to usbnet that Sierra
can set.

Dan

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