buck@siswat.UUCP (A. Lester Buck) (03/16/89)
I have been doing some driver development work under AIX and have run across the weirdest limitation in 2.2.1 (was in 2.2.0 also). It turns out AIX only wants to have 32 major device numbers (0 - 31). Well, you say, that doesn't sound so bad... But the system drivers reserve 0-19 (and only 4 and 19 are free on our system). And throw in a few things like SNA services (3 major numbers), a printer, the AT simulator, and a few things I can't remember leaves three open slots. Develop three new drivers (control driver, SCSI tape, SCSI WORM), and you are out of major numbers. But IBM has sold us WHIPS (3270 emulator stuff), which needs two major numbers. Or use a third party graphics system that chews up three numbers. Lots of IBM software still to add. And I have several more SCSI drivers to write... At least the automatic configuration subroutine (cfgadev) bombs out. If you add the device manually by editing /etc/master directly or building the number into the stanza ahead of time, then "devices" command will give really cryptic errors when you try to enable the device. And the *real* fun starts when you pick the obvious next free major number, 32, and then try to reboot. You see, something deep in the kernel effectively masks the bits to the range 0-31, 32->0, and the system disk driver is at major 0. :-( Now where was that Installation and Maintenance Disk? Our site now two completely different development machines with a different mix of software and devices, that both hit the wall today, unable to add new devices without deleting something. We have the Austin AIX team working on a fix, but I can't believe this is news to anybody with AIX source. Why would the designers limit things this way? I hope this is fixable, or it will be a *major* pain (pun intended). [ Charlie, are you listening? ;-) ] -- A. Lester Buck ...!texbell!moray!siswat!buck