The dev_t expansion

Linux has had 8-bit major/minor numbers since 1991
"Who needs more than 64K devices?"
This number space has gotten increasingly cramped
2.5 finally expands that space

Required changes to drivers are small
Unmodified char drivers will work 
(modulo other changes, of course)
New block interface already works

To support more devices (char drivers)
Update internal structures to handle larger minors
Request a larger space from the kernel
This interface still under development