Date: Thu, 30 Jan 1997 08:29:10 -0600 From: "Eric L. Hernes" <erich@lodgenet.com> To: Michael Smith <msmith@atrad.adelaide.edu.au> Cc: mcgovern@spoon.beta.com (Brian J. McGovern), hackers@freebsd.org Subject: Re: Cases (was: Constructive Criticism) Message-ID: <199701301429.IAA29130@jake.lodgenet.com> In-Reply-To: Your message of "Thu, 30 Jan 1997 14:22:44 %2B1030." <199701300352.OAA26563@genesis.atrad.adelaide.edu.au>
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Michael Smith writes:
>#define CDEV_MAJOR 20
>static struct cdevsw foo_cdevsw =
>{
> fooopen, fooclose, fooread, foowrite,
> fooioctl, nullstop, nullreset, nodevtotty,
> fooselect, nommap, NULL, driver_name,
> NULL, -1
>};
>
>Note that some of the placeholders are "no*" and some are "null*" - I
>think that this is laziness on someone's part 8(
I think that the `no' routines return ENODEV as an error, and
the `null' routines silently do nothing. Probably only for
the ones that make sense though. If you set d_open to
be nullopen, your device will work. If you set it to noopen,
open("/dev/mydev") will always fail. Some of them are just
#defined to be the other though, like d_reset and d_stop.
glance through sys/kern/subr_xxx.c and sys/sys/conf.h if you
care. ;-)
>
>--
>]] Mike Smith, Software Engineer msmith@gsoft.com.au [[
>]] Genesis Software genesis@gsoft.com.au [[
>]] High-speed data acquisition and (GSM mobile) 0411-222-496 [[
>]] realtime instrument control. (ph) +61-8-8267-3493 [[
>]] Unix hardware collector. "Where are your PEZ?" The Tick [[
>
eric.
--
erich@lodgenet.com
http://rrnet.com/~erich erich@rrnet.com
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