Make yocto download more sources after unpacking

Question

I have a recipe which references source A via the SRC_URI variable. However inside source A there is somewhere a link to another source B. I'd like to let Yocto download and unpack source A. Then I would parse the URL for source B from source A and tell Yocto to go back to downloading and unpacking source B. Is this possible?

The build process for source A would download source B itself, but I'd like Yocto to add source B to its DL_DIR to avoid downloading it again for the next build.

Answer 1

You can use Bitbake's fetcher to fetch more sources.

It's important to note that the fetcher will still use the SRCREV variable, even if you append something like ;rev=xxx to your URL. So you should set SRCREV to either None or "AUTOINC".

python do_loadSources() {
  # Backup SRCREV
  mySrcRev = d.getVar('SRCREV')
  d.setVar('SRCREV', None)
  
  # Somehow determine source URL
  sourceUrl = ...

  # Create fetcher
  fetcher = bb.fetch2.Fetch([ sourceUrl ], d)

  # Download
  fetcher.download()

  # Get path of downloaded sources
  fetcher.localpath(sourceUrl)

  # Use the downloaded sources
  ...

  # Restore SRCREV
  d.setVar('SRCREV', mySrcRev)
}

addtask do_loadSources after do_configure before do_compile