Re: dummy help on io

[Randy.Dunlap]

Gene Heskett wrote:
> On Sunday 12 December 2004 19:11, Randy.Dunlap wrote:
>
> > 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:
> > http://lwn.net/Kernel/LDD2/
>
>
> 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).
> >  http://ieee.uow.edu.au/~daniel/software/robotd/
>
>
> <http://ieee.uow.edu.au/~daniel/software/PIO/>
>
> > > 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.


--
~Randy
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