From: Alan Stern <stern@rowland.harvard.edu>
To: Paul Zimmerman <pauldzim@gmail.com>
Cc: Greg KH <greg@kroah.com>,
David Heinzelmann <heinzelmann.david@gmail.com>,
USB list <linux-usb@vger.kernel.org>
Subject: Re: [PATCH] USB: hub: Don't record a connect-change event during reset-resume
Date: Fri, 31 Jan 2020 16:04:12 -0500 (EST) [thread overview]
Message-ID: <Pine.LNX.4.44L0.2001311559490.1577-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <20200131123653.2ef373e4@EliteBook>
On Fri, 31 Jan 2020, Paul Zimmerman wrote:
> > Note that performing the unnecessary check is not actually a bug.
> > Devices are supposed to be able to send descriptors back to the host
> > even when they are busy doing something else. The underlying cause of
> > Paul's problem lies in his Bluetooth adapter. Nevertheless, we
> > shouldn't perform the same check twice in a row -- and as a nice side
> > benefit, removing the extra check allows the Bluetooth adapter to work
> > more reliably.
>
> Actually, at the time the failure happens, the bluetooth driver is putting
> the device into a "manufacturer mode" and downloading a firmware patch to
> the device. So I don't think we can fault the device for not responding to
> a get-descriptor request at that point. Probably there should be some kind
> of locking in the driver while that is being done.
Heh. We don't have any locking of that sort in the kernel. Any user
at any time can run "lsusb -v" and that program will try to communicate
with every attached USB device. There's no way to claim exclusive
rights to a device.
The fact that firmware loading works at all is more or less a matter of
luck (although the odds are with us).
> Nevertheless, your patch makes everything work again, so I think it's
> "good enough" :)
>
> Thanks,
> Paul
You're welcome.
Alan Stern
prev parent reply other threads:[~2020-01-31 21:04 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-31 15:39 [PATCH] USB: hub: Don't record a connect-change event during reset-resume Alan Stern
2020-01-31 19:36 ` Paul Zimmerman
2020-01-31 21:04 ` Alan Stern [this message]
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