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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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