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

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Date:	Mon, 3 Nov 2014 13:32:46 -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 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?

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.

>
>> 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?

Since EFI capsules are apparently on their way to becoming a
ubiquitous mechanism, I think it might be time to rethink
request_firmware for this.

--Andy
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