I spend quite a lot of time triaging bugs in Fedora for stuff I maintain upstream. The most common crasher bug I come across is colord segfaulting deep in libsane. Digging even more, 99% of those libsane crashers are when the user has installed closed source binary drivers to make the scanner “work”.
Of course, segfaulting colord just because it automatically assigns color profiles to scanners is not a good idea, even if we can blame non-free code. Something had to be done, as it was starting to make colord look bad as all the display and print color management would suddenly stop working in quite a dramatic way.
Now, in an ideal world, there would be a scanner daemon, scannerd, that I could patch for colord support, just like we’re doing for printers and dispays. This would then register devices with colord, and if it crashed, it could be autorestarted. Such a thing doesn’t exist, and so I had to do something that involved separating the libsane code from the main colord process.
In git master I’ve added a tiny dbus daemon called colord-sane, that basically does nothing except for rescanning sane whenever a USB device is plugged in and creating and deleting devices in colord. It only has one method “Refresh” and it is started when colord is started (usually in early boot) if the UseSANE=true option is specified in /etc/colord/colord.conf
In an ideal world, someone could take that code, and make a proper scannerd or saned project that adds some DeviceAdded and DeviceRemoved signals, a GetDevices() method and some more properties on each device, hopefully using something l33t like GDBusObjectServer. This would mean that the session could just use that for device discovery (e.g. in Simple Scan) and the world would be a much nicer place.
So, if you see a tiny colord-sane process show up in your system that’s not doing anything, don’t panic. You can disable the functionality if you know you’ll never have a scanner attached.