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

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Date:	Sun, 1 Jan 2012 22:39:13 +0100
From:	Michael Büsch <m@...s.ch>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Matthew Garrett <mjg@...hat.com>,
	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.

On Sun, 1 Jan 2012 22:27:56 +0100
Oliver Neukum <oliver@...kum.org> wrote:

> Ideally usbcore would deal with such devices, but at present the USB layer
> is unable to cleanly resume devices that change their IDs during
> resume.
> Solving this would mean putting all firmware loaders into kernel space.
> And the mode switching logic as well.

I don't get it. Why would a device enter a state after resume, that it was not
in at _any_ time before the machine was suspended?

These change-id-on-bootstrap devices usually work like this,
as far as I know:

probe bootstrap device (switches hw to real device)
probe real device (firmware is loaded)
Suspend machine
Resume machine
usb detects that the device is "gone"
probe/resume bootstrap device (switches hw to real device)
probe/resume real device (No need to fetch fw from userspace. It's already cached)

What did I get wrong?

-- 
Greetings, Michael.
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