On a server where i was updating slackware i had the need to use mkinitrd, because on this machine there was an hardware SCSI
controller (mtpspi kernel module) and an ext4 root partition, as usual i typed:
mkinitrd -c -k 3.10.30-smp -m mtpspi:ext4 -f ext4 -r /dev/sdb2 -l it -u
but after checking initrd-tree directory i found mtpspi* modules were missing.
Instead these were included if i typed:
mkinitrd -c -k 3.10.30-smp -m ext4:mtpspi -f ext4 -r /dev/sdb2 -l it -u
Perhaps modules searching (and dependencies) are affected by the alphabetical names.
This could be a big problem because there is a risk that a machine like this refuses to boot.
A quick look at the file /sbin/mkinitrd version 1.4.8 module search should be around line 624.