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

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Message-ID: <CA+55aFx=AEG7X2Y-LoHchgPdwNpeSkBG1J7eXprmO=czEJOD2A@mail.gmail.com>
Date:	Mon, 2 Jan 2012 13:00:45 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jack Stone <jwjstone@...tmail.fm>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Oliver Neukum <oliver@...kum.org>,
	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 Mon, Jan 2, 2012 at 12:55 PM, Jack Stone <jwjstone@...tmail.fm> wrote:
>
> The problem comes with knowing when to put the firmware - how do we tell
> the generic driver that that device has firmware that might need to be
> freed on disconnect. I don't know enough about USB to know if we can
> tell if the same device has reconnected due to firmware being loaded or
> if it was simply unplugged and a new device plugged in.

Well, if we just have a 10-second timeout for the firmware flushing
after the last "put" operation, we don't even care.

It doesn't even *matter* if the device is a physically different
device - if the driver loads the same firmware, it will be cached, and
it will still be correct for that (physically different, but with the
same firmware requirements) device. So even the whole "user switched
devices around" issue is irrelevant.

Of course, if the driver is some piece-of-crap that explicitly loads
the wrong firmware for the device it manages, the firmware will be
wrong, but hey, "Don't do that then". The drivers job very much
includes being able to look at the device ID (whether USB or PCIe or
PCMCIA) and figure out which firmware image it needs to load.

                   Linus
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