linux-kernel - Re: [GIT *] Allow request_firmware() to be satisfied from in-kernel, use it in more drivers.

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Message-Id: <1216150616.27455.377.camel@shinybook.infradead.org>
Date:	Tue, 15 Jul 2008 12:36:56 -0700
From:	David Woodhouse <dwmw2@...radead.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Marcel Holtmann <marcel@...tmann.org>,
	Frans Pop <elendil@...net.nl>, jeff@...zik.org,
	arjan@...radead.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, linux-kernel@...r.kernel.org
Subject: Re: [GIT *] Allow request_firmware() to be satisfied from
	in-kernel, use it in more drivers.

On Tue, 2008-07-15 at 12:27 -0700, Linus Torvalds wrote:
> 
> On Tue, 15 Jul 2008, Marcel Holtmann wrote:
> > 
> > using /lib/firmware/`uname -r`/ is actually not a bad idea. You only
> > have to fix udev to actually include this in the list of directories to
> > look for firmware files. Also Ubuntu is already doing this.
> 
> I really don't think we need to even "fix udev".
> 
> Why don't we just load it ourselves? Esepcially as there are probably 
> places that try to avoid udev entirely, or at least use a very 
> cut-down-version.
> 
> We should be fairly trivially able to be _entirely_ backwards compatible 
> with any sane setup (not the _sane_ part! It implies that people don't 
> copy individual modules around by hand!), with no actual breakage or need 
> for distros to even update anything at all - just make the kernel able to 
> look up binary blobs in the same place it installed them.
> 
> That sounds like the RightThing(tm) to do _regardless_ of any other 
> issues, doesn't it? If the kernel installs it in some known place, why 
> should it not just read them from that known place?

I'm unconvinced that the kernel should be setting this kind of policy.

But I suppose if you make it tunable in sysfs and just switch to calling
do_filp_open() directly from firmware_class.c instead of punting to
userspace, that might work.

It leaves you with less flexibility -- it would prevent stuff like the
udev trick I posted a week or so back to fix the Intel microcode loader
by automatically generating the needed binary blob on the fly from
microcode.dat, for example.

We also have a long tradition of pointing and laughing at people who
want to call open() from within the kernel. But it _could_ work,
certainly.

I'm not really convinced it helps though. The script which creates an
initrd still needs to look at the MODULE_FIRMWARE() tag and include the
right firmware file. If that's broken, you're screwed anyway. And that
was true in 2.6.25 too.

-- 
dwmw2

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