Re: cdevsw_add() vs make_dev()
:Wouldn't it be cleaner to give every driver its own major number? Maybe I
:really need to read 4.4 D&I or something like that to understand what I'm
:talking about.
:
:cheers
: simon
No, there aren't enough major numbers to go around. The pty's alone
would eat them all up.
e.g. 'ad' eats a major number. The minor number is then broken down into
a unit, like 'ad0', slice, like 'ad0s1', and partition, like 'ad0s1a'.
So for the 'ad' major number you already have a ton of possible minor
number combinations:
(taken from sys/disklabel.h) 32 bit device id
/*
3 2 1 0
1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
_________________________________________________________________
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
-----------------------------------------------------------------
| TYPE |UNIT_2 |P| SLICE | MAJOR | UNIT |PART |
-----------------------------------------------------------------
*/
so e.g. ad[0-511]s[0-15][a-p]
UNIT SLICE PARTITION
There are only 256 major numbers.
-Matt
Matthew Dillon
<dillon@backplane.com>
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