[PATCH RFC 6/6] binman: doc: update Optional entries

[Yannic Moog]

On Thu, 2025-02-13 at 07:01 -0700, Simon Glass wrote:
> Hi Yannic,
> 
> On Thu, 13 Feb 2025 at 00:21, Yannic Moog <Y.Moog at phytec.de> wrote:
> > 
> > On Mon, 2025-02-10 at 06:08 -0700, Simon Glass wrote:
> > > On Wed, 29 Jan 2025 at 03:30, Yannic Moog <y.moog at phytec.de> wrote:
> > > > 
> > > > The binman documentation of Optional entries is not accurate in the
> > > > sense that it does not cover blobs entry type. As this is also the most
> > > > widely used type to have the optional entry, document the interaction
> > > > with faking blobs.
> > > > 
> > > > Signed-off-by: Yannic Moog <y.moog at phytec.de>
> > > > ---
> > > >  tools/binman/binman.rst | 9 ++++++++-
> > > >  1 file changed, 8 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/tools/binman/binman.rst b/tools/binman/binman.rst
> > > > index 990fc295770..2bafa6ca408 100644
> > > > --- a/tools/binman/binman.rst
> > > > +++ b/tools/binman/binman.rst
> > > > @@ -1145,7 +1145,14 @@ called on all entries.
> > > >  It is not possible for an entry to mark itself absent at any other point in the
> > > >  processing. It must happen in the ObtainContents() method.
> > > > 
> > > > -The effect is as if the entry had never been present at all, since the image
> > > > +The effect depends on the type of entry.
> > > > +
> > > > +Blobs
> > > > +~~~~~
> > > > +For blobs, the effect depends on whether --fake-ext-blobs is passed
> > > > +to binman. (This is the case by default)
> > > > +In case --fake-ext-blobs is set, any missing entries will be faked.
> > > > +If not set, it is as if the entry had never been present at all, since the image
> > > >  is packed without it and it disappears from the list of entries.
> > > 
> > > I'm not quite following this. The text seems OK but your heading
> > > implies that things other than blobs can be faked. All of this
> > > functionality is only for blobs.
> > 
> > The heading is a subsection of "Optional entries". To my knowledge the "optional" property is
> > not
> > limited to blobs. But blobs get special treatment in regards to "optional" due to the --fake-
> > ext-
> > blobs option. Hence the subsection.
> > 
> > What would you like me to change to make this clearer?
> 
> Oh I see. Are you saying that optional entries end up in the image
> when they are faked, external blobs? If so, that seems like a bug to
> me.

To clarify, optional images are faked only when they are missing. So in case the image is missing, a
faked image is indeed packaged into the image.

Here is the image map from an (phycore-)imx8mp build.

Missing tee-os (faked):

ImagePos    Offset      Size  Name
00000000  00000000  00159e10  image
00000000   00000000  00159e10  section
[...]
00058000    00058000  00101e10  fit
0005b000     00003000  000e4910  uboot
0005b000      00000000  000e4910  blob-ext
0013f910     000e7910  00008458  atf
0013f910      00000000  00008458  atf-blob
00147d68     000efd68  00000000  tee
00147d68      00000000  00000000  tee-os

tee-os present:

ImagePos    Offset      Size  Name
00000000  00000000  0022b5b0  image
00000000   00000000  0022b5b0  section
[...]
00058000    00058000  001d35b0  fit
0005b000     00003000  000e4910  uboot
0005b000      00000000  000e4910  blob-ext
0013f910     000e7910  00008458  atf
0013f910      00000000  00008458  atf-blob
00147d68     000efd68  000d17a0  tee
00147d68      00000000  000d17a0  tee-os

Yannic

> 
> Regards,
> Simon