Re: [Qemu-devel] fw_cfg specification ?

[Laszlo Ersek <lersek@redhat.com>]

On 03/11/15 16:27, Gabriel L. Somlo wrote:
> Hi,
> 
> I'm looking for the closest thing to an official spec for qemu's
> fw_cfg device, and so far I have found this:
> 
> http://lists.gnu.org/archive/html/qemu-devel/2011-04/msg00238.html
> 
> but it apparently never got committed to qemu (any idea why not?).

Must have fallen through the cracks. (Just speculating; in April 2011 I
had been with RH for less than half a year, and learning Xen. :))

> Googling around didn't get me much further than that.
> 
> Is there anything better or more up to date floating around out
> there somewhere ?

I won't say "better", but it is "committed": check
"Documentation/devicetree/bindings/arm/fw-cfg.txt" in the kernel tree.
It is intentionally vague on the set of keys and fw_cfg files that qemu
provides, because that's a moving target. You can only rely on the qemu
source for those.

Also, I updated Gleb's email address in the CC: header.

If you have a ton of time, you could try documenting fw_cfg yourself,
but as I said, it's a moving target, so the description would either
become stale quickly, or require people to keep it in sync with the
source all the time. Updating documentation sucks *hard*.

(At one point I had also started a text file like Jordan's, but I didn't
even get as far as posting it anywhere; I just gave up.)

Thanks
Laszlo