[PATCH] schemas: Add schema for firmware logs

[Rob Herring]

+boot-architecture

On Mon, Feb 6, 2023 at 3:25 PM Simon Glass <sjg at chromium.org> wrote:
>
> Hi Rob,
>
> On Mon, 6 Feb 2023 at 10:15, Rob Herring <robh at kernel.org> wrote:
> >
> > On Sat, Feb 4, 2023 at 6:04 AM Simon Glass <sjg at chromium.org> wrote:
> > >
> > > Hi Peter,
> > >
> > > On Sat, 4 Feb 2023 at 02:36, Peter Robinson <pbrobinson at gmail.com> wrote:
> > > >
> > > > Hi Simon,
> > > >
> > > > Does it make sense to devise something that is compatible with the
> > > > kernel's pstore [1] mechanism?
> > >
> > > Possibly...can you please be a little more specific?
> >
> > Peter is talking about the same thing I suggested on IRC.
> >
> > pstore == ramoops
>
> Oh, I only looked at the DT binding as I thought that was what you
> were talking about on irc.

The binding is called ramoops as it's for the RAM backend for pstore.

My suggestion was either using/extending ramoops or following its
design as a reserved memory region. All you would need to extend the
ramoops binding is a new property to define the size of your data.

> For pstore, isn't the point that Linux wants to save stuff to allow
> debugging or collection on reboot? What does that have to do with
> console logs from firmware? That seems like a different thing. Or are
> you suggesting that we add a pstore driver into U-Boot? It is quite a
> lot of code, including compression, etc. It might be easier for Linux
> to write the data into pstore when it starts up?

Originally ramoops was just what you described. It has grown to
multiple backends and types of records (hence the rename to pstore).
If you just add a new subsection within the pstore region, then I
think the existing kernel infrastructure will support reading it from
userspace. Maybe new types have to be explicitly supported, IDK.

U-boot being able to read pstore wouldn't be a terrible feature to
have anyways if your boot crashes before anything else is up to get
the output. Note I'd guess the ram backend doesn't do compression as
supporting slightly corrupted ram is a feature which wouldn't work.


I think any new DT binding is premature and pstore/ramoops was just a
suggestion to consider. This needs wider consideration of how to
handle all the various (boot) firmware logs. I've added the
boot-architecture list for a bit more visibility.

Rob