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

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Message-ID: <20141103212706.GE7379@kroah.com>
Date:	Mon, 3 Nov 2014 13:27:06 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Andy Lutomirski <luto@...capital.net>
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 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.

> 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?

> And you most certainly don't want the EFI capsule hanging around so that
> it might be accidentally installed again if the hard disk is moved.
> 
> ISTM there should be some file in sysfs to which you can write a
> capsule, or perhaps a chardev and an ioctl.

No, just use the firmware interface please.

thanks,

greg k-h
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