From owner-freebsd-arch  Tue Feb 13 22: 2:50 2001
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Date: Tue, 13 Feb 2001 22:02:36 -0800 (PST)
From: Matthew Jacob <mjacob@feral.com>
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To: Poul-Henning Kamp <phk@critter.freebsd.dk>
Cc: arch@freebsd.org
Subject: Re: now that DEVFS is standard.... 
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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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