linux-kernel - Re: [PATCH v6 2/5] efi: Add embedded peripheral firmware support

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Message-ID: <20180607155702.GA5527@wotan.suse.de>
Date:   Thu, 7 Jun 2018 17:57:02 +0200
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Julia Lawall <julia.lawall@...6.fr>,
        Martijn Coenen <maco@...roid.com>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, Peter Jones <pjones@...hat.com>,
        Dave Olsthoorn <dave@...aar.me>,
        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>,
        dmitry.torokhov@...il.com, mfuzzey@...keon.com,
        Arend Van Spriel <arend.vanspriel@...adcom.com>,
        nbroeking@...com, Torsten Duwe <duwe@...e.de>,
        Kees Cook <keescook@...omium.org>, x86@...nel.org,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/5] efi: Add embedded peripheral firmware support

On Thu, Jun 07, 2018 at 03:46:11PM +0200, Hans de Goede wrote:
> On 06-06-18 23:42, Luis R. Rodriguez wrote:
> > On Wed, Jun 06, 2018 at 08:39:15PM +0200, Hans de Goede wrote:
> > > On 05-06-18 23:07, Luis R. Rodriguez wrote:
> > > 2) Should this flag then be checked inside _request_firmware() before it
> > > calls fw_get_efi_embedded_fw() (which may be an empty stub),
> > 
> > You are the architect behind this call, so its up to you.
> > 
> > To answer this you have to review the other flags and see if other users of the
> > other flags may want your functionality. For instance the Android folks for
> > instance rely on the FW_OPT_NOFALLBACK - the sysfs fallback mechanism to
> > account for odd partition layouts. Could they ever want to use your fallback
> > mechanism? Granted your mechanism is for x86, but they could eventually add
> > support for it on ARM.
> > 
> > Checking if the firmware is on the EFI platform firmware list is much faster
> > than the fallback mechanism, that would be one gain for them, as such it may
> > make sense to check for firmware_request_platform() before using the sysfs
> > fallback mechanism.  However if Android folks want to always override the
> > platform firmware with the sysfs fallback interface we'd need another flag
> > added and call to then change the order later if we checked for for the
> > platform firmware first.
> 
> I believe we agreed a while back that the platform fallback would
> replace the sysfs one when requested. I believe that still makes
> sense. If a driver wants both it can simply call request_firmware_foo
> itself twice and determine the order itself.

Fine by me, so in your case the syfs fallback will be ignored.

Which gets me thinking that perhaps we should have a separate
syfs fallback call. There are only two drivers that use it
explicitly:

  o CONFIG_LEDS_LP55XX_COMMON
	request_firmware_nowait(THIS_MODULE, false, ...);
  o CONFIG_DELL_RBU
	request_firmware_nowait(THIS_MODULE, FW_ACTION_NOHOTPLUG, ...)

And FW_ACTION_NOHOTPLUG is 0.

The above revelation of the async call being data driven is a good
opportunity to break that tradition to the more preferred functional
one. And so we'd also get rid of the FW_ACTION_NOHOTPLUG option
all together.

So a new firmware_request_sysfs_async() I suppose.

  Luis