Re: [RFC PATCH 15/15] Introduce v18 dtb version

[Herve Codina <herve.codina@bootlin.com>]

Hi Luca,

On Wed, 01 Apr 2026 17:19:09 +0200
"Luca Ceresoli" <luca.ceresoli@bootlin.com> wrote:

> On Tue Feb 10, 2026 at 6:33 PM CET, Herve Codina wrote:
> > This v18 version will add support for
> >   - Structured tags.
> >     Those tags value definition will allow old libfdt, dtc and other
> >     tools to skip unknown tags if encountered in future dtb version.  
> 
> "old" seems to imply that versions released before today will be able to
> wkip unknown tags. I think this should be clarified along the lines of:
> 
>   libfdt, dtc and other tools implementing version v18 will be able to wkip
>   unknown tags in dtbs generated with later versions of dtc

Yes, I will add this clarification in the next iteration.

> 
> >   - dt_flags header field.
> >     For now this flag field is set to 0. It is a placeholder for future
> >     dtb version and could be used to store some dtb related information
> >     such as the kind of dtb.  
> 
> Is this intended for DT addons?
> 
> You may mention a realistiv use case here.

Intended, maybe not. Used by addons, yes, for sure.

What do you think if I add the following:
    For instance, the future addons format will use this field to
    clearly identify that the dtb is an addon dtb.

...
> >
> > Compared to previous version, it is worth noting that the dtb is not  
>                                                                ^
> 				                        "dtb version"
> 
> > downgrade for all modification but only when unknown tags are removed  
>   ^
>   downgraded for any
> 
> 
> > due a property modification.  
>   ^
>   "due to a ..."
> 
> I'm not sure I got what you mean by the initial "Compared to previous
> version". Version(s) of what?
> 
> If I just remove those 4 words the sentence seems OK to me BTW.

Is the following clearer?

    It is worth noting that with this v18 version, the dtb version is not
    downgraded for any modification but only when unknown tags are removed
    due to a property modification. In v17 or older version any modification
    led to a dtb version downgrade.

Best regards,
Hervé