This is really strange. Yesterday I spent some time to track this issue and provide here more info, so I removed the custom udev rule to restart hplip service and... it works !?!? There is no more needs to restart the hplip service to use both scanned and printer feature.
I've no idea why this occurred. I tried to unplug and plug, remove the printer entry in CUPS and readd. Nothing: the printer works as it should. Sorry for the unuseful report. However, I'll attach the printingbuginfo.txt file, the syslog entries turning on the device and the sane dedug (export SANE_DEBUG_DLL=128) output. Currently the only issue is related to `hp-setup` utility from "hplip" package. It seems that tool check ppd files in /usr/share/ppd/hpijs/HP/ but in default Ubuntu installation only HP-Fax-hplip.ppd.gz is available here. Other PPDs from hplip project are installed by "hpijs-ppds". So, if you use `hp-setup` to setup your HP printer in base Ubuntu installation and you don't point to a specific PPD outside the previous dir, your HP device will print like a fax :-( -- Need to restart hplip service to use HP c3100 https://launchpad.net/bugs/81477 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
