Re: [PATCH] usb: uas: fix usb subsystem hang after power off hub port

From: Alan Stern
Date: Fri Mar 08 2019 - 12:33:19 EST

On Fri, 8 Mar 2019, Oliver Neukum wrote:

> On Fr, 2019-03-08 at 09:13 +0000, Kento.A.Kobayashi@xxxxxxxx wrote:
> > The usb_reset_and_verify_device included in usb_reset_device fails
> > with -ENODEV after power off hub port, and the -ENODEV error will
> > be reported to uas_eh_bus_reset_handler and upper layer, so it
> > doesn't need to do rebind if -ENODEV happens.
> Hi,
> no I am sorry, that is an assumption you just cannot make.
> Anything can trigger a reset. That being SCSI is the common
> case certainly, but not the only case. And in those cases
> we cannot depend on upper layers doing the right thing, if
> we just ignore an error.
> Sorry
> Oliver

Note that the reset routines in usb-storage do not make any exceptions
for -ENODEV.

Alan Stern