Hi Laurent, On Sun, 3 Dec 2023 at 08:33, Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > > Hi Simon, > > Thank you for the patch. > > On Fri, Dec 01, 2023 at 08:54:42PM -0700, Simon Glass wrote: > > Add a script which produces a Flat Image Tree (FIT), a single file > > containing the built kernel and associated devicetree files. > > Compression defaults to gzip which gives a good balance of size and > > performance. > > > > The files compress from about 86MB to 24MB using this approach. > > > > The FIT can be used by bootloaders which support it, such as U-Boot > > and Linuxboot. It permits automatic selection of the correct > > devicetree, matching the compatible string of the running board with > > the closest compatible string in the FIT. There is no need for > > filenames or other workarounds. > > > > Add a 'make image.fit' build target for arm64, as well. Use > > FIT_COMPRESSION to select a different algorithm. > > > > The FIT can be examined using 'dumpimage -l'. > > > > This features requires pylibfdt (use 'pip install libfdt'). It also > > requires compression utilities for the algorithm being used. Supported > > compression options are the same as the Image.xxx files. For now there > > is no way to change the compression other than by editing the rule for > > $(obj)/image.fit > > > > While FIT supports a ramdisk / initrd, no attempt is made to support > > this here, since it must be built separately from the Linux build. > > FIT images are very useful, so I think this is a very welcome addition > to the kernel build system. It can get tricky though: given the > versatile nature of FIT images, there can't be any > one-size-fits-them-all solution to build them, and striking the right > balance between what makes sense for the kernel and the features that > users may request will probably lead to bikeshedding. As we all love > bikeshedding, I thought I would start selfishly, with a personal use > case :-) This isn't a yak-shaving request though, I don't see any reason > to delay merging this series. OK, sounds good! > > Have you envisioned building FIT images with a subset of DTBs, or adding > DTBOs ? Both would be fairly trivial extensions to this script by > extending the supported command line arguments. It would perhaps be more > difficult to integrate in the kernel build system though. This leads me > to a second question: would you consider merging extensions to this > script if they are not used by the kernel build system, but meant for > users who manually invoke the script ? More generally, is the script > meant to be used stand-alone as well, in which case its command line > arguments need to remain backward-compatible, or do you see it as being > internal to the kernel ? The script as written is internal to the kernel, but I am sure it could be expanded in some ways. I am waiting to see it merged before worrying too much about what might happen in the future! [..] Regards, Simon
