Re: [RFC PATCH v2 0/4] Add device tree build information

[Alexandre Torgue]

Hi Franck

On 2/28/20 6:47 PM, Frank Rowand wrote:
> Hi Alexandred,
>
> Ping.

Sorry I was off last week.

> -Frank
>
>
> On 2/21/20 11:47 AM, Frank Rowand wrote:
> > On 2/21/20 10:14 AM, Alexandre Torgue wrote:
> > > (with title it's better ;)
> > >
> > > Hi,
> > >
> > > The goal of this series is to add device tree build information in dtb.
> > > This information can be dtb build date, where devicetree files come from,
> > > who built the dtb ... Actually, same kind of information that you can find
> > > in the Linux banner which is printout during kernel boot. Having the same
> > > kind of information for device tree is useful for debugging and maintenance.
> > >
> > > A file (dtb-build.txt) containing a string with build information (e.g.,
> > > >From Linux 5.5.0-rc1 by alex the Mon Jan 13 18:25:38 CET 2020) is generated by
> > > "gen_dtb_build_info.sh" script.
> > >
> > > This file has to be included manually in each dts file that would like to use
> > > this build information.
> >
> > In the RFC series, you said:
> >
> >    "I gonna prepare a V2 with David proposition (to use overlay format) by
> >     keeping in mind not to modify existing dts(i) files."
> >
> >     https://lore.kernel.org/linux-devicetree/9d83a36c-78c5-3452-bb48-209d68c46038@xxxxxx/
> >
> > But here in v2 instead requires including dtb-build.txt.
> >
> > This would require modifying every single main .dts file to get the build info
> > I would prefer the method that Ian and David came up with (sorry, no lore link,
> > it did not go to lkml).  Extract from David's email:
> >
> >     Date:   Tue, 21 Jan 2020 13:05:25 +1100
> >     From:   David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
> >     Subject: Re: [RFC PATCH 1/3] dtc: Add dtb build information option
> >
> >     > Given that dts files are run through the C preprocessor before being
> >     > fed to dtc, the build script could use the '-include' flag to force-
> >     > include a fragment containing generated build info without any need to
> >     > modify existing dts files.
> >
> >     Uh... maybe.  -include will essentially prepend the forced file, which
> >     is a bit awkward for our purposes.  It means that the prepended file
> >     would need the /dts-v1/ tag, and we couldn't have it in the main files
> >     which would be a bit confusing.  I think it would also cause problems
> >     with any /memreserve/ tags and means that the main tree could in
> >     theory overwrite the build information which we don't necessarily
> >     want.
> >
> >     I guess we could build things the other way around: have the main .dts
> >     file specified with -include and have the dts on the dtc commandline
> >     be a fixed one with the build information.  It'd be a little weird,
> >     though.
> >
> > -Frank

Yes. I try briefly this idea but I got issues with dts-v1 tag. I agree, 
it is cleaner to not modify input dts file. I can rework int this way.

regards
Alex

> > > of/fdt.c is modified to printout "build-info" property during Kernel boot and
> > > scripts/Makefile.lib is modified to call "gen_dtb_build_info.sh" script.
> > >
> > > Patch 1 & 2 script and of/fdt.c updates
> > > Patch 3 is an example of use in stm32mp157c-dk2.dts file.
> > > Patch 4 is a tentative to make it automatic (not yet 100% functional).
> > >
> > > regards
> > > Alex
> > >
> > > Changes since v1;
> > >   - Remove modification in dtc (no more -B option)
> > >   - Generate a file containing build info which is directly included in dts
> > >     file.
> > >
> > >
> > > Regards
> > > Alex
> > >
> > > Alexandre Torgue (4):
> > >    scripts: Add script to generate dtb build information
> > >    of: fdt: print dtb build information
> > >    ARM: dts: stm32: Add dtb build information entry for stm32mp157c-dk2
> > >    script: make automatic dtb build info generation
> > >
> > >   arch/arm/boot/dts/stm32mp157c-dk2.dts |  1 +
> > >   drivers/of/fdt.c                      |  9 +++++++++
> > >   scripts/Makefile.lib                  |  3 +++
> > >   scripts/gen_dtb_build_info.sh         | 12 ++++++++++++
> > >   4 files changed, 25 insertions(+)
> > >   create mode 100755 scripts/gen_dtb_build_info.sh