linux-kernel - Re: [PATCH v4 2/2] efi: an sysfs interface for user to update efi firmware

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Date:	Wed, 15 Apr 2015 17:19:09 -0700
From:	Roy Franz <roy.franz@...aro.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Matt Fleming <matt@...sole-pimps.org>,
	Ong Boon Leong <boon.leong.ong@...el.com>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	Sam Protsenko <semen.protsenko@...aro.org>,
	"Kweh, Hock Leong" <hock.leong.kweh@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Jones <pjones@...hat.com>,
	Ming Lei <ming.lei@...onical.com>
Subject: Re: [PATCH v4 2/2] efi: an sysfs interface for user to update efi firmware

On Wed, Apr 15, 2015 at 8:45 AM, Andy Lutomirski <luto@...capital.net> wrote:
> On Apr 15, 2015 6:20 AM, "Greg Kroah-Hartman"
> <gregkh@...uxfoundation.org> wrote:
>>
>> On Tue, Apr 14, 2015 at 11:52:48AM -0400, Andy Lutomirski wrote:
>> > On Tue, Apr 14, 2015 at 10:09 AM, Greg Kroah-Hartman
>> > <gregkh@...uxfoundation.org> wrote:
>> > > On Tue, Apr 14, 2015 at 05:44:56PM +0800, Kweh, Hock Leong wrote:
>> > >> From: "Kweh, Hock Leong" <hock.leong.kweh@...el.com>
>> > >>
>> > >> Introducing a kernel module to expose capsule loader interface
>> > >> for user to upload capsule binaries. This module leverage the
>> > >> request_firmware_direct_full_path() to obtain the binary at a
>> > >> specific path input by user.
>> > >>
>> > >> Example method to load the capsule binary:
>> > >> echo -n "/path/to/capsule/binary" > /sys/devices/platform/efi_capsule_loader/capsule_loader
>> > >
>> > > Ick, why not just have the firmware file location present, and copy it
>> > > to the sysfs file directly from userspace, instead of this two-step
>> > > process?
>> >
>> > Because it's not at all obvious how error handling should work in that case.
>>
>> I don't understand how the error handling is any different.  The kernel
>> ends up copying the data in through the firmware interface both ways, we
>> just aren't creating yet-another-firmware-path in the system.
>
> If I run uefi-update-capsule foo.bin, I want it to complain if the
> UEFI call fails.  In contrast, if I boot and my ath10k firmware is
> bad, there's no explicit user interaction that should fail; instead I
> have no network device and I get to read the logs and figure out why.
> IOW bad volatile device firmware is just like a bad device driver,
> whereas bad UEFI capsules are problems that should be reported to
> whatever tried to send them to UEFI.
>
> --Andy
>
There are several types of errors that can be returned by
UpdateCapsule(), allowing
us to distinguish between capsules that are not supported by the
platform, capsules
that must be updated at boot time, and capsule updates that failed due
to a device error.
I think we really do want this type of information returned to capsule loader.

Roy

>>
>> thanks,
>>
>> greg k-h
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