linux-kernel - Re: [PATCH v2 0/3] Enable user helper interface for efi capsule update

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Message-ID: <CALCETrVuRgzHyxscK39DnnW2nDrs0jGHz5uSRKASgpUHENgnLA@mail.gmail.com>
Date:	Mon, 3 Nov 2014 17:14:54 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Kweh Hock Leong <hock.leong.kweh@...el.com>,
	Matt Fleming <matt.fleming@...el.com>,
	Ming Lei <ming.lei@...onical.com>,
	Sam Protsenko <semen.protsenko@...aro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-efi@...r.kernel.org,
	Ong Boon Leong <boon.leong.ong@...el.com>
Subject: Re: [PATCH v2 0/3] Enable user helper interface for efi capsule update

On Mon, Nov 3, 2014 at 4:38 PM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Mon, Nov 03, 2014 at 03:08:08PM -0800, Andy Lutomirski wrote:
>> On Mon, Nov 3, 2014 at 3:02 PM, Greg Kroah-Hartman
>> <gregkh@...uxfoundation.org> wrote:
>> > On Mon, Nov 03, 2014 at 01:32:46PM -0800, Andy Lutomirski wrote:
>> >> On Mon, Nov 3, 2014 at 1:27 PM, Greg Kroah-Hartman
>> >> <gregkh@...uxfoundation.org> wrote:
>> >> > On Mon, Nov 03, 2014 at 11:33:23AM -0800, Andy Lutomirski wrote:
>> >> >> On 11/02/2014 07:07 PM, Kweh Hock Leong wrote:
>> >> >> > From: "Kweh, Hock Leong" <hock.leong.kweh-ral2JQCrhuEAvxtiuMwx3w@...lic.gmane.org>
>> >> >> >
>> >> >> > Hi Guys,
>> >> >> >
>> >> >> > This patchset is created on top of "efi: Capsule update support" patch:
>> >> >> > http://permalink.gmane.org/gmane.linux.kernel.efi/4837
>> >> >> >
>> >> >> > It leverages the request_firmware_nowait() to expose the user helper interface for user to upload the capsule binary and calling the
>> >> >> > efi_capsule_update() API to pass the binary to EFI firmware.
>> >> >>
>> >> >> I don't get it.  Why is the firmware interface at all reasonable for
>> >> >> uploading capsules?
>> >> >
>> >> > Tradition dictates that BIOS updates go through the firmware interface,
>> >> > that way you don't have to write a new userspace tool, which is a good
>> >> > thing.
>> >> >
>> >> >> The firmware interface makes sense for nonvolatile firmware where
>> >> >> hotplugging something or otherwise loading a driver needs a blob.
>> >> >
>> >> > Or BIOS data.  We've been doing it this way for a long time now.
>> >>
>> >> On what system?  Dell?
>> >
>> > Yes.
>> >
>> >> IMO this sucks from a UI point of view.  When I install wifi firmware,
>> >> I expect to stick it somewhere and have the driver find it, because
>> >> the driver knows exactly when it needs the firmware.  When I update my
>> >> BIOS, I want to click a button or type a command and update my bios.
>> >
>> > I agree, it should be "triggered" by something, not just automagically
>> > loaded whenever the kernel randomly looks for it.
>> >
>> >> >> But uploading an EFI capsule is an *action*, not something that should
>> >> >> happen transparently.  If there's an EFI firmware update available and
>> >> >> the user wants to install it, then the userspace tool should install it,
>> >> >> and it shouldn't hang around in /lib/firmware.  In fact, you shouldn't
>> >> >> even need /lib to be on writable media to use this.
>> >> >
>> >> > What does /lib have to do with this?
>> >>
>> >> Where else does the file come from, given that udev no longer supports
>> >> userspace firmware loading?  Is there really some pre-existing tool
>> >> that pokes it into the sysfs firmware class thing?
>> >
>> > Well, you can specify other locations than /lib/firmware/ for firmware
>> > updates, but yes, you are right, it should be in /lib somewhere.  But
>> > /lib doesn't need to be writable, it's a read-only file.
>> >
>>
>> I assume that whoever downloaded the firmware update will want to
>> install it, right?  I don't really expect distros to ship EFI capsules
>> in packages that install to /lib/firmware.  Won't there be userspace
>> code that either installs a capsule from some URL or uses some future
>> magical find-my-firmware service?
>
> Good point, I don't know.
>
> Who ever wrote this code should know this, can someone please provide a
> use-case for how this is all supposed to work?

There's a partial description here:

http://download.microsoft.com/download/5/f/5/5f5d16cd-2530-4289-8019-94c6a20bed3c/windows-uefi-firmware-update-platform.docx

It looks like there may need to be a way to atomically load several
capsules in the same UpdateCapsule call so that userspace can do fancy
things like ask for an image to be displayed while the update is
applied.

--Andy
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