linux-kernel - Re: [RFC PATCH 00/13] firmware loader: introduce cache/uncache firmware

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Date:	Wed, 25 Jul 2012 14:43:29 +0200
From:	Oliver Neukum <oneukum@...e.de>
To:	Ming Lei <ming.lei@...onical.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Borislav Petkov <borislav.petkov@....com>,
	linux-kernel@...r.kernel.org, Matthew Garrett <mjg@...hat.com>,
	linux-usb <linux-usb@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [RFC PATCH 00/13] firmware loader: introduce cache/uncache firmware

On Wednesday 25 July 2012 20:35:28 Ming Lei wrote:
> CC usb guys and list
> 
> On Wed, Jul 25, 2012 at 1:53 AM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > I really think the isight thing is a totally different thing entirely.
> >
> > And quite frankly, that's just a BUG in the USB implementation. If the
> > USB ID changes, it shouldn't be considered a "resume" thing at all,
> > but a probe thing, and that should not be done in early resume - it
> > should be done *after* the resume is done.
> 
> IMO, usbcore may have found the ID changes during resume(reset_resume),
> and make the device disconnect. The disconnect event will be handled
> in hubd kthread, which is woken up before usermodehelper_enable()(see
> thaw_processes), so request_firmware will return failure during probe()
> inside hubd kthread.
> 
> The cache firmware patch set may not help the situation, because the
> original isight usb device for downloading firmware has been disconnected
> before system suspend, so firmware loader can't cache the firmware for
> the device.
> 
> The below patch should fix the problem above.

This is likely unwise. You'd better introduce a special flag for kernel threads
that should be thawed only after user space will have been thawed.

	Regards
		Oliver

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