Messages in this thread |  | | Date | Mon, 1 Jul 96 10:23 CDT | Subject | Re: SCSI device numbering | From | (Johnie Stafford) |
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>>>>> "ac" == Albert Cahalan <albert@ccs.neu.edu> writes:
ac> From: eric@aib.com (Eric Youngdale) >> >>> Anyway, I think we should be ok with a 12+20 bit dev_t, >>> that sounds like the best solution right now. >> >> OK, but the point was that 20 bits for a minor number is >> insufficient for a fixed mapping of devices to minor numbers. >> It would be sufficient if we wanted to continue to use dynamic >> mapping of minors to devices, of course.
ac> No, it is sufficient for everything, including really weird ac> SCSI adapters. Using nibble boundries (for nice hex output), ac> dev_t can be split as follows:
ac> Purpose Bits Normal Extreme ac> controller 4 <= 1 2 ac> bus 4 == 0 1 ac> device 8 <= 2 4
What about wide SCSI? It does 16 devices.
ac> lun 8 == 0 3 ac> partition 4 <= 3 4
What about an entry for the entire disk (eg. /dev/sda)? What about logical partitions? If you include the entry for the entire disk, I use 9 entries for my primary disk.
ac> Note that the number of bits allowed is far more than normally ac> needed and is sufficient for every system reported to the kernel ac> list. The extra 4 bits can be left reserved or used for the ac> (rather artificial IMHO) distinction between disk and CD or ac> whatever.
I think you are about 10 or 12 bits short.
Johnie
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