Re: [Qemu-devel] [PATCH] parport EPP support for Linux

[Marko Kohtala]

Fabrice Bellard:
> Marko Kohtala wrote:
>
>    Hi.
>
>    With the attached patch I am able to use Kodak Advantix FD 300 APS
>    scanner from Win98 when hosted under Linux ix86. It adds EPP support
>    and fixes some register bits to match real hw so port identification
>    works better.
>
>    I tried to separate the linux dependencies with #ifdef __linux__, but
>    can not test this does not break compilation for other ports of qemu.
>
> I don't understand why you need a #ifdef __linux__ in parallel.c.
Normally, the qemu >character device should suffice to do the
appropriate abstraction.

I did not find appropriate abstraction. Linux parallel device needs to
do a read() on the device. A read() on the parallel port device
executes EPP read cycle on the parallel port to read from the device
attached to it. Poll() does not execute such cycles, but it only
signals read if the port makes an interrupt, and therefore the current
poll() based character device abstraction does not work.

So there are few read() and write() calls in the code.

Also the parallel port device IEEE mode settings use some constants
from linux/parport.h. These are needed to tell the device execute EPP
data or address cycles on reads and writes.

I am too new with qemu to say how to develop the qemu character device
abstraction for these requirements.

Marko