El Sun, Aug 07, 2022 at 04:33:26PM -0600, Simon Glass deia:
This is an attempt to answer the comments provided by Xavier [1].
Thank you. Sorry if I point out silly things too. No agony intended.
+Note that binman can itself can create a FIT. This helps to move mkimage
one "can" too much
+invocations out of the Makefile and into binman image descriptions. It also +helps by removing the need for ad-hoc tools like `make_fit_atf.py`.
Maybe in future tense? We're not there yet?, because of tee.bin, see Jerome's message. Or is tee.bin not officialy supported yet in U-Boot?
+How do you know how to incorporate ATF? It is handled by the atf-bl31 entry type +(etype). An etype is an implementation of reading a binary into binman, in this +case the `bl31.bin` file. When you build U-Boot but do not set the BL31 +environment variable, binman provides a help message, which comes from +`missing-blob-help`::
- See the documentation for your board. You may need to build ARM Trusted
- Firmware and build with BL31=/path/to/bl31.bin
+The mechanism by which binman is advised of this is also in the Makefile. See +the `-a atf-bl31-path=${BL31}` piece in `cmd_binman`. This tells binman to +set the EntryArg `atf-bl31-path` to the value of the `BL31` environment +variable. Within binman, this EntryArg is picked up by the `Entry_atf_bl31` +etype. An EntryArg is simply an argument to the entry. The `atf-bl31-path` +name is documented in :ref:`etype_atf_bl31`.
Still confused. Shouldn't you mention split-elf ? The way I use it bl31.elf is not simply copied into an image (atf_bl31.py is just a Entry_blob_named_by_arg). It is sliced in pieces and put into u-boot.itb. Each piece carries a little metadada like the load address, extracted from the elf by make_fit_atf.py or binman with split-elf.
The problem is binman cannot incorporate an image it produced as a binary into another, so we must still use make_fit_atf.py. But then binman does not use atf-bl31, it simply includes a blob with filename="u-boot.itb".
Maybe it's not the best way to do it and people should just add a atf-bl31 {} section in their binman image and it somehow works ? Because that's what I would assume from your text.
Or maybe you're talking of other boards, but then try not to write it as this is the method one uses always when one has atf (TF-A)?
Anyway, thank you for writing it. The docs help understand many of the issues and are a good improvement.