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    SubjectRe: dummy help on io
    Gene Heskett wrote:
    > Greetings;
    > I've ordered the device drivers book from O-Reilly but it will be
    > a few days getting here.

    Get it online:

    > I'm trying to mod the GPL'd archive PIO.tar.gz, so it will build a
    > driver for a pci card with 3 each 82C55's on it, and I *think* I'd
    > have it working with the first of the 3 chips if I could figure
    > out what to do about using the call "iopl(3);" on installing
    > the driver, and conversely an "iopl(0);" at rmmod time.

    Where is that coming from? I don't see it in the tarball
    or the web site (if I'm looking at the right place).

    > I'm told this is required to gain access perms to addresses above
    > 0x3FF. The call "ioperm" is used below that I've been told.

    iopl() and ioperm() are userspace calls that call (g)libc.
    The kernel doesn't call them.

    > Unforch, an "insmod PIO io=0xf100" (where the card is addressed
    > at currently) is spitting out an "unresolved symbol" error for the
    > iopl call.
    > Being a rank beginner at "pc" hardware, can someone give me a
    > checklist of things I've probably left out please?

    Can you put the iopl() call into your app instead?
    or into a shell script that forks the app (since the iopl
    man page says: Permissions are inherited by fork and exec.)

    > Kernel is 2.4.25-adeos. With the module "rtai" inserted when emc
    > is running for realtime control purposes.
    > The card is pure hardware, no bios, only address decoding that
    > can set the base address anyplace in the first 64k of address
    > space in a step of 4 sequence from 0xnn00-0xnn0C for the 4
    > ports of chip 1, 0xnn10-1C for chip 2, etc, where the nn is the
    > dipswitch setting.

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