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

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On Wed, Mar 6, 2013 at 12:08 AM, Bjørn Mork <bjorn@xxxxxxx> wrote:
> Ming Lei <ming.lei@xxxxxxxxxxxxx> 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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