To try and get an essential device working I have installed the kernel from /testing in Slackware64-13 being vmlinuz-generic-126.96.36.199. I am running this system from an external USB drive (for now) and have managed (eventually) to get this to boot with 188.8.131.52 supplied kernel.
To do this I had to suuply a "rootdelay=" stanza to lilo for the huge kernel and add several devices to the initrd for the generic. Here is my command to create an initial ram disk (works with 184.108.40.206):
mkinitrd -c -k 220.127.116.11 -m ehci-hcd:usb-storage:ext3 -f ext3 -r /dev/sdc5 -w 20"
All this works fine with 18.104.22.168 but the newer kernel hangs with the old unable to load from root device errors. These are what caused me to investigate the rootdelay and additional kernel modules options in the first place!
Anyway - as the kernel in /testing is only supplied in generic (not huge) form I have tried rebuilding this with the huge .config and "make oldconfig". This kernel errors out the same as the supplied generic one with my added modules.
Looking at the screen I can see the rootdelay working but the drive is not being spun up - this means the "unable to mount root" problem is crashing it.
I find it odd that all this worked fine with the old kernel but not with the new. From boot message observation it looks like the drivers I supplied to the initrd (ehci-hcd:usb-storage) may not be getting loaded and causing the boot to crash. Hopefully all this isn't going to mean 2.6.29 is the end of the line for my hardware support (no - I'm being too pessimistic there). Trouble is I don't know where to look next !
Any ideas more than welcome.