While reading the description of CONFIG_BLK_DEV_BSG (Block Layer SG support v4) in the kernel, I noticed the following text: "This option is required by recent UDEV versions to properly access device serial numbers, etc." For that reason, it may be prudent to add it to CONFIG_CHECK so that the user is warned in case of its absence.
I checked the udev changelog, and it looks like this is suggested since udev-145. Zzam, should we add it to all of those ebuilds?
I have added this check to all affected versions of udev in the tree.