Re: question about usb_rebind_intf

[Mathias Nyman]

On 17.11.2017 19:09, Greg Kroah-Hartman wrote:
> On Fri, Nov 17, 2017 at 09:35:51AM -0700, Jerry Snitselaar wrote:
> > Should this skip warning that the rebind failed if device_attach
> > is returning -EPROBE_DEFER? If I do something like 'rtcwake -m mem -s 30'
> > on a laptop I have here I will see a couple "rebind failed: -517" messages
> > as it comes back out of suspend. Since the device probe eventually happens
> > once probes are not deferred wondering if this warning this be given in that
> > case.
> >
> >
> > diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
> > index 64262a9a8829..5d3408010112 100644
> > --- a/drivers/usb/core/driver.c
> > +++ b/drivers/usb/core/driver.c
> > @@ -1070,7 +1070,7 @@ static void usb_rebind_intf(struct usb_interface *intf)
> >         if (!intf->dev.power.is_prepared) {
> >                 intf->needs_binding = 0;
> >                 rc = device_attach(&intf->dev);
> > -               if (rc < 0)
> > +               if (rc < 0 && rc != -EPROBE_DEFER)
> >                         dev_warn(&intf->dev, "rebind failed: %d\n", rc);
> >         }
> > }
>
> What USB driver is returning -EPROBE_DEFER to cause this to be an issue?
> Shouldn't that really only be for "platform" drivers and the like?  USB
> interface drivers should all be "self-contained" within reason.

I see this as well with btusb driver in resume if port was reset.

drivers/base/dd.c really_probe() returns -EPROBE_DEFER if it's called before
device_unblock_probing() is called.

drivers/base/power/main/dpm_complete() will unlock probing after it has
finished resuming all devices and called all the pm_ops .complete callbacks.

The usb_device_pm_ops .complete callback will try to rebind the interface driver
if device was reset at resume, leading to them -EPROBE_DEFER.
 
I guess we either need to rework a few things, or remove that warning.

-Mathias