Subject: DMA troubles
To: None <>
From: Filka Michal <>
List: tech-kern
Date: 03/22/2006 16:11:55
Hi all,
I did a driver for a device (a HDLC controller, particulary), but there
is problem that the device is not able to do a DMA read access into
memory. Better to say that it seems so.

I have a reason to think that the device is able to do a DMA write.
Particulary, I'm able to get meaningful interrupt vectors which are
filled by the device using DMA write access. However, I'm not able to
force the device to send any data, it means read a descriptor using DMA.
In fact I know nothing particular about descriptor's data, but
interrupts (which I can request throught descriptor's flags) are not

Driver's code is a port of my driver for the same device but for another
OS and it works well there. So, I suppose that there is some mistake in
my usage of NetBSD's DMA capabilities.

Any ideas are very welcome.

Michal Filka