Re: [PATCH stblinux.git 1/2] dt-bindings: firmware: add Broadcom's NVRAM memory mapping

[Rafał Miłecki]

On 08.03.2021 22:37, Rafał Miłecki wrote:
> On 08.03.2021 19:43, Rob Herring wrote:
> > On Tue, Mar 02, 2021 at 08:44:04AM +0100, Rafał Miłecki wrote:
> > > From: Rafał Miłecki <rafal@xxxxxxxxxx>
> > >
> > > NVRAM structure contains device data and can be accessed using MMIO.
> > >
> > > Signed-off-by: Rafał Miłecki <rafal@xxxxxxxxxx>
> > > ---
> > >   .../bindings/firmware/brcm,nvram.yaml         | 41 +++++++++++++++++++
> > >   1 file changed, 41 insertions(+)
> > >   create mode 100644 Documentation/devicetree/bindings/firmware/brcm,nvram.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/firmware/brcm,nvram.yaml b/Documentation/devicetree/bindings/firmware/brcm,nvram.yaml
> > > new file mode 100644
> > > index 000000000000..12af8e2e7c9c
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/firmware/brcm,nvram.yaml
> > > @@ -0,0 +1,41 @@
> > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: "http://devicetree.org/schemas/firmware/brcm,nvram.yaml#";
> > > +$schema: "http://devicetree.org/meta-schemas/core.yaml#";
> > > +
> > > +title: Broadcom's NVRAM
> > > +
> > > +maintainers:
> > > +  - Rafał Miłecki <rafal@xxxxxxxxxx>
> > > +
> > > +description: |
> > > +  NVRAM is a structure containing device specific environment variables.
> > > +  It is used for storing device configuration, booting parameters and
> > > +  calibration data.
> >
> > The structure of the data is fully discoverable just from a genericish
> > 'brcm,nvram'?
>
> Yes, NVRAM structure is a header (with magic and length) and a list of
> key-value pairs separated by \0. If you map memory at given address you
> should verify magic and start reading key-value pairs.
>
> Content example: foo=bar\0baz=qux\0quux(...)
>
> There is no predefined order of pairs, set of keys or anything similar I
> could think of. I can't think of anything more worth describing in DT.

Ah, I've just realized, I'm replying to the "firmware" binding patch.

Florian suggested to look at NVMEM subsystem instead. Please kindly check
[PATCH V2 1/2] dt-bindings: nvmem: add Broadcom's NVRAM