Re: Can we kill f inb_p, outb_p and other random I/O on port 0x80, in 2.6?

From: Alan Cox (alan_at_lxorguk.ukuu.org.uk)
Date: 09/22/03

  • Next message: Alan Cox: "Re: [PATCH] PnP Fixes for 2.6.0-test5" 
    To: "Eric W. Biederman" <ebiederm@xmission.com>
Date:	Mon, 22 Sep 2003 12:22:59 +0100

    On Llu, 2003-09-22 at 01:27, Eric W. Biederman wrote:
    > So can we gradually kill inb_p, outb_p in 2.6? An the other
    > miscellaneous users of I/O port 0x80 for I/O delays?
    >
    > Or possibly rewriting outb_p to look something like:
    > outb(); udelay(200); or whatever the appropriate delay is?

    The delay should be 8 ISA clocks. While you can easily fix inb_p and
    outb_p you also need to fix up the udelay() code since if you stick
    a BUG() check in udelay you'll find it gets used before the clock is
    initialized even now, let alone with inb_p relying on it. But that
    itself is quite fixable too.

    (one part of the problem of course is you need inb_p/outb_p to drive
    the timer chip on some x86 boards in order to calibrate the udelay
    timer)

    > When debugging this I modified arch/i386/io.h to read:
    > #define __SLOW_DOWN_IO__ ""
    > Which totally removed the delay and the system ran fine.

    Not all systems do - we had breakages from both the keyboard controller
    and the timer chips even on some modern boards when this got messed up.

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