Subject: Can I access ISA bus and PGIO pins through /dev/mem?
To: None <email@example.com>
From: Anders Lindgren <firstname.lastname@example.org>
Date: 06/11/2007 14:14:20
Hi everyone, and especially Jesse Off if you're reading. :-)
Playing around with my TS7250 board and its TS7KV framebuffer, and NetBSD
I am trying to access the fb on the PC/104 bus from user space by simply
mmap:ing /dev/mem, following the board's [Linux] example code. This way,
I've been able to identify the board on the bus, load the FPGA bitmask
into the FPGA, ACK the loading, and activate the FPGA. It lights its green
LED. :-) However, I get no visible video output apart from a brief flicker
before the screen goes blank again.
Before I dig any deeper into this -- is this method going to work at
all? I've seen comments to the effect that some X drivers do pretty much
this, and I'd like to use the same method to bang on some EP9302 GPIO pins
as well. Or do I have to modify the tsarm startup or write a stub open +
mmap driver somehow to tell NetBSD not to cache these address ranges?
As long as the kernel realizes that the physical ISA addresses I mmap
are non-cachable side effect memory locations, it should Just Work(tm)? I
figured the tsarm "isaio" node somehow takes care of this somewhere during
startup, but reading the code didn't tell me much, as I am not yet
familiar with how the bus space framework works.
I'd like to play around in user space before I venture into figuring out
how to make a kernel driver for the card out of it. Please bring out ye
olde cluebats for a NetBSD kernel newbie. :-)