Re: [PATCH 2.6] Altix serial driver

From: Russell King (rmk+lkml_at_arm.linux.org.uk)
Date: 06/28/04

  • Next message: Vasant Tiwari: "Non-free bits in linux kernel" 
    Date: 	Mon, 28 Jun 2004 02:14:39 +0100
To: Chris Wedgwood <cw@f00f.org>

    On Sun, Jun 27, 2004 at 05:33:11PM -0700, Chris Wedgwood wrote:
    > On Sun, Jun 27, 2004 at 07:24:34PM -0500, Erik Jacobson wrote:
    > > Maybe you can help me clear it up then. When I feed serial core the
    > > name ttyS with TTY_MAJOR and minor 64, the registration fails. If I
    > > disable 8250 in the kernel config, the registration works for us.
    >
    > I'm not sure why the 8250 code reserves/registers ttyS0 on Altix when
    > do such hardware exists. I vaguely recall patching it to prevent this
    > in a hacky way.
    >
    > I would like to know why the 8250 code is registering a driver for
    > hardware that doesn't exist and see that fixed.

    It's the way its always been done, and the way the tty layer works.
    You register a range of ttys that you're going to be driving, and
    you own those ttys whether or not you actually have hardware for
    them.

    You can't say "ok, I have ttyS1 and ttyS3, I'll leave ttyS0 and ttyS2
    available for someone else to use" because the tty layer just doesn't
    work like that. It has the notion of a single driver for a range of
    non-overlapping ttys.

    Yes, it would be nice to get rid of that limitation, but we're in a
    stable kernel series and the tty layer doesn't have a maintainer to
    do the work... 

    -- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 PCMCIA      - http://pcmcia.arm.linux.org.uk/
                 2.6 Serial core
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