Re: PICs on Linux

[Bart Oldeman <bartoldeman@users.sourceforge.net>]

Hello,

> The printer driver and DOSEMU's port passing cannot share
> the physical printer port.  Therefore you need to disable
> the printer driver if you want to use DOSEMU's port
> passing, either temporarily or permanently.
>
> Yes, and remember to use 'fast' unless you want to do
> debugging/tracing: $_ports = "fast range 0x378 0x37a"
>
> means pass through 0x378-0x37a in fast mode.
>
> You have to start DOSEMU as root or use sudo in order for
> port/irq passing to work.

It's still a bit tricky. This is the nature of direct
hardware access under Linux, the jail around you (protected
mode OS) needs to be partially broken down. There are
security issues to deal with, etc etc. -- this is why we can
never let this happen out of the box for a normal (non-root)
user.

This is not unique to Linux, under Windows XP there are even
people trying to make a buck selling direct hardware access.
http://www.zeecube.com/ParPort2004.htm
we don't ask for $19.95 but you have to pay in other ways
(trickier setup) so to speak.

However:
Linux 2.4 and 2.6 kernels provide a ppdev device driver that
allows raw parallel port access via /dev/parports/0 etc.
DOSEMU could virtualize the parallel port hardware and
re-route it through that device thereby avoiding the root
issue. I don't have any parallel port hardware to play with
but it could be a nice little project to implement in DOSEMU
one day.

Speed shouldn't be such a big deal: according to
http://www.ussg.iu.edu/hypermail/linux/kernel/0303.0/0978.html
you can only do about 300000 inb's and outb's per second
anyway.

Bart