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

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Message-Id: <201201031257.47265.oliver@neukum.org>
Date:	Tue, 3 Jan 2012 12:57:47 +0100
From:	Oliver Neukum <oliver@...kum.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Jack Stone <jwjstone@...tmail.fm>,
	Matthew Garrett <mjg@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	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 Dienstag, 3. Januar 2012, 01:42:20 schrieb Alan Cox:
> In that case however you don't want some generic firmware module knowing
> all this crap, your driver can just request_firmware() the stuff as
> modprobe and free it up on the module unload. For a typical 8bit firmware
> of a few K you'll free a ton more memory unloading the module than the
> firmware ! That I think actually covers the majority of devices under
> discussion.

I am afraid it doesn't, at least not fully.
We have many devices whose primary (operational) driver does not load
the firmware. That job is left to a secondary driver or user space.

We could leave those secondary drivers and their firmware in RAM after
their primary usage and except for a few pathological cases (which
can be solved with a few udev rules preventively loading drivers) we'd
be good, but we lack a mechanism for switching to a seconary driver
and back during resumption.

	Regards
		Oliver
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