linux-kernel - Re: loading firmware while usermodehelper disabled.

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Message-Id: <201201011322.34483.oliver@neukum.org>
Date:	Sun, 1 Jan 2012 13:22:34 +0100
From:	Oliver Neukum <oliver@...kum.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Matthew Garrett <mjg@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Larry Finger <Larry.Finger@...inger.net>,
	Chaoming Li <chaoming_li@...lsil.com.cn>,
	"John W. Linville" <linville@...driver.com>,
	"Greg Kroah-Hartman" <gregkh@...e.de>,
	USB list <linux-usb@...r.kernel.org>,
	Linux Wireless List <linux-wireless@...r.kernel.org>
Subject: Re: loading firmware while usermodehelper disabled.

Am Sonntag, 1. Januar 2012, 03:21:45 schrieb Alan Stern:
> On Sat, 31 Dec 2011, Oliver Neukum wrote:

> > We are definitely going through do_unbind_rebind(). But I don't think
> > it matters why we got there. We seem to be calling probe() too early.
> > And we need to guarantee that a driver can request firmware in probe()
> > 
> > So something has changed in the resume code path further up.
> 
> For at least a year and a half, it has been true that rebinding takes

Yes, so I don't understand why we haven't been hitting this issue
all that time.

> place during the complete phase of system resume.  Clearly that is too 
> early to load firmware.  When do you think we should do it instead?

I think we ought to delay until right after user space is unfrozen.
The devices are gone anyway, so we lose nothing but have the ability
to call helpers.
 
> And how should we keep track of which interfaces need rebinding?

I guess this calls for a brute force approach. We can kick khubd and have
it walk all busses checking for  needs_binding.

> P.S.: Oliver, it looks like there's a bunch of dead code in
> usb_suspend_interface() and usb_resume_interface().  I don't see how
> either one can be executed with a driver that doesn't have both suspend
> and resume methods.  Such cases should be filtered out when
> usb_suspend() calls do_unbind_rebind().  The only odd thing that can
> happen is when a driver doesn't support reset-resume.  Do you agree?

I agree.

	Regards
		Oliver
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