linux-kernel - Re: RFC: Moving firmware blobs out of the kernel.

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Date:	Thu, 29 May 2008 15:12:46 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	David Woodhouse <dwmw2@...radead.org>
CC:	Theodore Tso <tytso@....edu>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	James.Bottomley@...senPartnership.com,
	ksummit-2008-discuss@...ts.linux-foundation.org,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org
Subject: Re: RFC: Moving firmware blobs out of the kernel.

David Woodhouse wrote:
> I'm kind of hoping that this is going to be one of those topics that
> resolves itself -- but just in case it isn't, I'd like to discuss it at
> the kernel summit:
> 
> I'd like to remove all firmware blobs from the kernel source tree.
> 
> With the intention of making that less contentious, I've done the
> following: 
> 
> I've added support to the firmware loader for finding firmware in a
> special section of the static kernel, so that using request_firmware()
> no longer forces you to use an initrd or udev. You can build _arbitrary_
> firmware files into your kernel, if you want to. Whether you're allowed
> to distribute the resulting vmlinux or not is still a question you ought
> to ask your lawyer.
> 
> I'm working on converting drivers over to use request_firmware(), and
> shifting their firmware blobs into .ihex files in a firmware/ directory
> of the source tree. For each one, I'm giving the option of continuing to
> build it in statically, using the above mechanism.
> 
> I've implemented a 'make firmware_install' Kbuild target, which takes
> all those firmware blobs and installs them somewhere where udev can load
> them on request.
> 
> By the time the kernel summit comes around, we should have made decent
> progress on moving _all_ the firmware blobs to the firmware/ directory.
> And at that point I'd like to remove them completely, to a separate git
> tree and tarball. Those who really want to build them in to their static
> kernel would still be able to, but it wouldn't be the default behaviour.


I like your idea, all the way to the point where you actually remove the 
firmware file from the kernel tree :)

I think it's a good move to make the firmware files standalone and not 
#include'd as a C header file, but it's just plain easier to ship them 
with the kernel tree in a lot of cases.  $FOO-firmware packages in 
Fedora prove other methods of firmware distribution are quite usable, 
but that does not therefore imply that in-kernel built-in firmwares have 
no utility.

Personally, living in an imaginary all-open-source world, I wouldn't 
mind seeing firmware source for firmware built into drivers, a la 
drivers/scsi/aic7xxx/aicasm/, living in the kernel tree.

If the firmware has a compatible license and is required for critical 
operations like booting the machine, built-in firmware should remain an 
option.  For certain embedded cases, I could certainly see that 
in-kernel firmware being the best method for firmware distribution, for 
both $Platform's users and $Platform's developers.

	Jeff



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