netdev - Re: [PATCH 4/7] usbnet: cdc_mbim: don't recover device if suspend fails in system sleep

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Date:	Wed, 6 Mar 2013 10:51:50 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Bjørn Mork <bjorn@...k.no>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Kosina <jkosina@...e.cz>,
	Alan Stern <stern@...land.harvard.edu>,
	Oliver Neukum <oneukum@...e.de>, netdev@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [PATCH 4/7] usbnet: cdc_mbim: don't recover device if suspend
 fails in system sleep

On Wed, Mar 6, 2013 at 12:08 AM, Bjørn Mork <bjorn@...k.no> wrote:
> Ming Lei <ming.lei@...onical.com> writes:
>
> I am starting to wonder why the USB core has combined system suspend and
> runtime suspend if we are going to end up with every driver testing
> PMSG_IS_AUTO(message) and selecting a completely different code path.
>
> You are right that we will end up with problems if usbnet_resume is
> called for a device usbnet hasn't suspended.  But I'd still claim that
> is a bug in the USB core, which is the one that decided to ignore the
> suspend error and still call resume.
>
> I guess proper error handling here require the USB core to see the
> interface driver as dead if it fails to suspend on system suspend, and
> do forced rebinding on resume.

The idea should be fine, but may cause regression of user space, suppose
one device with suspend failure can be across suspend-resume cycle and
work well before, but it is no longer with your forced rebinding.

>
> I am not going to fight this any longer.  The per-driver
> PMSG_IS_AUTO(message) testing is an ugly workround for a core problem,
> but they are already all over the place...  Still, please make sure the
> drivers all return 0 if they are pretending to suspend. No error code
> return if the driver ignores the error.

I agree, resume() of driver has to handle the suspend failure if there is
the failure returned from suspend().

Thanks,
--
Ming Lei
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