linux-kernel - Re: [PATCH 2/2] efi: Add embedded peripheral firmware support

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Message-ID: <20180406140832.GF30543@wotan.suse.de>
Date:   Fri, 6 Apr 2018 14:08:32 +0000
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Lukas Wunner <lukas@...ner.de>
Cc:     Peter Jones <pjones@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kalle Valo <kvalo@...eaurora.org>,
        Arend Van Spriel <arend.vanspriel@...adcom.com>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Dave Olsthoorn <dave@...aar.me>, x86@...nel.org,
        linux-efi@...r.kernel.org, Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        David Howells <dhowells@...hat.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Josh Triplett <josh@...htriplett.org>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        dmitry.torokhov@...il.com, mfuzzey@...keon.com,
        keescook@...omium.org, nbroeking@...com,
        bjorn.andersson@...aro.org, Torsten Duwe <duwe@...e.de>
Subject: Re: [PATCH 2/2] efi: Add embedded peripheral firmware support

On Thu, Apr 05, 2018 at 07:43:49AM +0200, Lukas Wunner wrote:
> On Wed, Apr 04, 2018 at 01:18:36PM -0400, Peter Jones wrote:
> > > On Tue, Apr 03, 2018 at 08:07:11PM +0200, Lukas Wunner wrote:
> > > > * Add the EFI Firmware Volume Protocol to include/linux/efi.h:
> > > >   https://www.intel.com/content/dam/doc/reference-guide/efi-firmware-file-volume-specification.pdf
> > > > 
> > > > * Amend arch/x86/boot/compressed/eboot.c to read the files with the
> > > >   GUIDs you're interested in into memory and pass the files to the
> > > >   kernel as setup_data payloads.
> > 
> > To be honest, I'm a bit skeptical about the firmware volume approach.
> > Tools like UEFITool[0] and uefi-firmware-parser[1] have existed for
> > years, still don't seem to reliably parse firmware images I see in the
> > wild, and have a fairly regular need for fixes.  These are tools
> > maintained by smart people who are making a real effort, and it still
> > looks pretty hard to do a good job that applies across a lot of
> > platforms.
> > 
> > So I'd rather use Hans's existing patches, at least for now, and if
> > someone is interested in hacking on making an efi firmware volume parser
> > for the kernel, switch them to that when such a thing is ready.
> 
> Hello?  As I've written in the above-quoted e-mail the kernel should
> read the files using EFI_FIRMWARE_VOLUME_PROTOCOL.ReadFile().
> 
> *Not* by parsing the firmware volume!
> 
> Parsing the firmware volume is only necessary to find out the GUIDs
> of the files you're looking for.  You only do that *once*.

How do you get the GUIDs for each driver BTW?

Hans, I do believe we should *try* this approach at the very least.

Why not?

Otherwise it would be wise to provide a technical reason for why
we'd choose one custom mechanism which would only serve a few tablets
over a mechanism which could serve more devices.

  Luis