I have submitted a patch to the linux kernel that has gotten several reviews and gone through a couple iterations on the mailing list. It has been ACKed and reviewed by two developers, but they say it is up to a specific developer to approve the patch. This developer is relatively absent from the mailing list. I do not want to harass him personally, but I would like some sort of acknowledgement that the patch can or cannot be accepted. What is the best way to solicit feedback from this developer? Is it acceptable to send a private email to him or to one of the reviewers or is it important for all communication to be public through the mailing lists?
It's pretty standard practice to address the email directly to the direct maintainer (use the To: field) and CC any relevant people/lists. If you forgot to address the maintainer directly in the original thread, you're probably fine simply forwarding it to them.
Don't consider it personal harassment to send one email---anyone maintaining part of the kernel has to sift through a lot of email, and probably simply hasn't seen your patch because it wasn't addressed directly to them and so got lost in the noise. Of course, do your due diligence first---make sure that your change isn't already in their kernel tree (or patchwork, etc.) before you do that.