[oe] MACHINE_KERNEL_PR vs recipe PR

[Ian Geiser]

I am curious about the machine_kerne_pr class.  What is the advantage/difference between using MACHINE_KERNEL_PR to change the kernel recipe revision vs using PR in the recipe?  Shouldn't anything that DEPENDS on virtual/kernel get rebuilt if PR changes in the kernel recipe?  From what I can tell all it does anyway is set the PR value of whatever inherits it to MACHINE_KERNEL_PR. Or is there a use for this beyond just making sure a package gets rebuilt?

Thanks!