On Fri, 9 Feb 96 13:11:13 EST 
 Mike Long <mike.long@analog.com> wrote:

 > Is this really necessary?
 > 
 > While I haven't checked exhaustively, it looks like devices are put
 > into cfdata[] in ioconf.c in the same order as they are read from
 > .../conf/files.*.  If so, all one needs to do is make sure that (e.g.)
 > "ed" appears before "mcd", then add comments explaining why.

Umm ... I don't particularly like the idea of a device getting trashed 
because of the order in a config file... That order is, and should 
continue to be, arbitrary.

 > This proposed change will also slow autoconfiguration, because
 > config_search() must scan the entire cfdata[] array, instead of
 > short-circuiting as soon as it finds an eligible device instance.

Fortunately, in most cases, cfdata[] isn't that large.  Also, given that 
autoconfiguration only happens once, I'm not certain I'm worried about 
hurting its performance.  Also, how bad could it really be?  :-)

 > Doesn't the autoconfig system already have a prioritization scheme
 > (value returned by match routine), that ISA isn't using?

Yes, but in this case, the priority scheme is backwards.  The current 
priority scheme ("best match", basically) is employed by the MI SCSI 
code.  Thankfully, SCSI device probes aren't destructive.  However, it is 
worth noting that all of the *match() routines (sd, cd, st, uk, ch, etc.) 
get called.  The one with the highest "match priority".  The problem I'm 
attempting to solve with "probe priority" is the fact that some devices 
get munched if some other destructive probe somes along and peers at its 
io space.  In other words, I want to create a situation where the mcd 
driver won't probe because the ed driver will have already attached and 
allocated that ISA space from the resource map.

--------------------------------------------------------------------------
Jason R. Thorpe                                       thorpej@nas.nasa.gov
NASA Ames Research Center                               Home: 408.866.1912
NAS: M/S 258-6                                          Work: 415.604.0935
Moffett Field, CA 94035                                Pager: 415.428.6939