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

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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@linuxfoundation.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@public.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.

> 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.

What do you suggest instead?  A "custom" sysfs file?  What is going to
trigger it to be loaded?  A userspace script that someone else has to
write?  :)

thanks,

greg k-h