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    SubjectRe: dummy help on io
    Gene Heskett wrote:
    > On Sunday 12 December 2004 19:11, Randy.Dunlap wrote:
    >>Gene Heskett wrote:
    >>>I've ordered the device drivers book from O-Reilly but it will be
    >>>a few days getting here.
    >>Get it online:
    > Thanks, but my printer is down, I mde the mistake of installing
    > cups-1.1.22. But I'll go get it anyway.

    Sure, just look at it on-screen (or print very selected
    pages of it).

    >>>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.
    > So my driver module does need them?

    A kernel driver (whether built into vmlinux or a loadable
    module) cannot use them and does not need 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?
    > I can try it in the examples demo.c which I've modified to run
    > the motor 10 revolutions, if it runs. 1 step/sec. That runs
    > without any errors *if* I take the iopl() back out of the driver
    > and insmod it.
    >>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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