Re: [REVIEW] move tty lock/initial up in the stack

From: M. Warner Losh (imp_at_bsdimp.com)
Date: 06/20/04

  • Next message: Poul-Henning Kamp: "Re: [REVIEW] move tty lock/initial up in the stack" 
    Date: Sun, 20 Jun 2004 10:50:00 -0600 (MDT)
To: phk@phk.freebsd.dk

    In message: <82937.1087721102@critter.freebsd.dk>
                "Poul-Henning Kamp" <phk@phk.freebsd.dk> writes:
    : In an ideal world the hardware driver would be reduced to just that,
    : a few simple primitives, "start", "config", "open", "close" and a
    : backcall "rint" with received data and modem status changes. This
    : is not too unlike what Marcel have done with uart(4)

    I guess I'm curious how the tty/cua split would be done in this
    scheme.

    Of course I'm reimplementing the Cyclades Z driver to try to use
    uart, which is why I'm getting curious. I don't know if this will
    wind up working or not, but since 95% of the hardware interface is two
    circular buffers in memory, which does seem to map mostly onto
    Marcel's model. Time will tell... I also have porting the stallion
    driver to current. I can do this by a simple hack on the old driver,
    or a rewrite. I'll use my Z experience to decide.

    : The major difference is that serial ports are rapidly headed into
    : the sunset whereas disks are very much a hot topic.

    I suspect that the decline will last for a long time. Many of the usb
    devices that I've seen are really usb to rs232 to thing, so I suspect
    that it is a case of 'Serial ports are dead, long live the serial
    ports'

    : The pty driver is the only really interesting tty driver these days
    : as most terminal access is through sshd, telnetd or xterm.

    There's still a lot of people using ppp for dialup connections, even
    in the day of broadband. I suspect that will be the other large area
    of heavy use.

    : Currently I see two ways to get ptys out form under giant:
    :
    : 1) write an entirely new pty driver which is totally separate
    : from the rest of the tty code (We don't need slip/ppp/netgraph
    : support on ptys anyway).
    :
    : 2) clean up the tty code enough that the pty can be deGiantized,
    : paving the road for the rest of the tty drivers to get the
    : same treatment, should somebody else care enough.

    Are you looking for help on the latter?

    : I havn't quite made up my mind yet, and have resorted to some general
    : polishing while I try to make sense of this stuff. To some extent I
    : already regret getting my fingers dirty over here.

    OK.

    Warner
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  • Next message: Poul-Henning Kamp: "Re: [REVIEW] move tty lock/initial up in the stack"

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