Date: Fri, 19 Dec 1997 22:01:05 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: julian@whistle.com (Julian Elischer) Cc: gurney_j@resnet.uoregon.edu, mike@smith.net.au, avalon@coombs.anu.edu.au, freebsd-hackers@FreeBSD.ORG Subject: Re: converting drivers to dynamic memory... Message-ID: <199712192201.PAA17466@usr05.primenet.com> In-Reply-To: <3499E71A.167EB0E7@whistle.com> from "Julian Elischer" at Dec 18, 97 07:16:42 pm
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> The AIM is that after a cut-over to devfs, > drivers could be modified to take more generalised arguments. > > the minor number can be interpretted as a cookie that can be used to > look something up in a hash-table or similar. > > That's what I do in slice/slice_device.c > the minor number there is just a cookie, that is used to find > a softc structure. In a more generalised situation. > the minor could be used to find a small structure > which in turn contains a pointer to the softc, plus a unique > sub-identifier. > > eventually, the minor number might be interpretted directly as a > pointer to this structure. > > Since teh minor number is supplied by the driver and never > alterable by the user, this is safe. it might also be > possible to make it not print out at all in 'ls' > as that would just be confusing. > > What I'm saying is that the minor number can be interpretted > as the driver sees fit, however in the current system it must > be a static thing and that is very limiting. (not to mention > we only have 24 bits) One thing that kind of concerns me... there will remain a need to be able to NFS export statically generated device nodes of the old style. FreeBSD won't need them, but... you could be net-booting a diskless or dataless client off a FreeBSD box. Such a client would need the traditional device nodes. This is more an issue to deal with mknod, and not necessarily through the provision of a specfs hook in your FS that you are exporting (ie: it's a referential issue that FreeBSD itself can ignore, so long as mknod can make the nodes that the client can interpret through its own specfs). Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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