Date: Tue, 13 Feb 2001 22:02:36 -0800 (PST) From: Matthew Jacob <mjacob@feral.com> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: arch@freebsd.org Subject: Re: now that DEVFS is standard.... Message-ID: <Pine.LNX.4.21.0102132159120.21365-100000@zeppo.feral.com> In-Reply-To: <55329.982130096@critter>
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> In message <Pine.LNX.4.21.0102131839460.21365-100000@zeppo.feral.com>, Matthew
> Jacob writes:
> >
> >....Can we now have wildcarded major numbers for creating devices?
> >
> >I mean, now that we have the name just appear each time you boot, the actual
> >major number is not all that relevant now, is it?
>
> Weeeeeeell, devfs is default, but not mandatory so we still support
> running !devfs systems, and unfortunately I suspect we will do so
> for some time still.
How about us having a 'range' of numbers, so we can do things like:
static struct cdevsw sa_cdevsw = {
/* open */ saopen,
/* close */ saclose,
/* read */ physread,
/* write */ physwrite,
/* ioctl */ saioctl,
/* poll */ nopoll,
/* mmap */ nommap,
/* strategy */ sastrategy,
/* name */ "sa",
/* maj */ SA_CDEV_ANY,
/* dump */ nodump,
/* psize */ nopsize,
/* flags */ D_TAPE,
/* bmaj */ -1
};
or
static struct cdevsw sa_cdevsw = {
/* open */ saopen,
/* close */ saclose,
/* read */ physread,
/* write */ physwrite,
/* ioctl */ saioctl,
/* poll */ nopoll,
/* mmap */ nommap,
/* strategy */ sastrategy,
/* name */ "sa",
/* maj */ SA_CDEV_MAJOR|SA_CDEV_ANY,
/* dump */ nodump,
/* psize */ nopsize,
/* flags */ D_TAPE,
/* bmaj */ -1
};
(make_dev gets SA_CDEV_MAJOR if !devfs, else any old number will do....)
We went round and round and round with this at Sun. We ended up with the
persistent file /etc/name_to_major which then binds a driver to a particular
major. I've *never* liked it- so prone to porking.
However, I like distributed, hemi-demi-asssigned, majors even less.
Just some thoughts.
-matt
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