This has come up a couple times recently*, so here's a proposal as to
one way of fixing the problem in the bus_dma API
BUS_DMA(9)
NAME
bus_dma, ..., bus_dma_tag_parent
SYNOPSIS
#include <machine/bus.h>
....
bus_dma_tag_t
bus_dma_tag_parent(device_t dev);
....
FUNCTIONS
....
bus_dma_tag_parent(dev)
Returns the DMA tag of the bus dev connects to. Drivers can use the
DMA tag for the parent parameter in subsequent calls to
bus_dma_tag_create(9). All devices on a bus share this tag as their
parent and should not destroy it.
Returns NULL if tag does not exist or a bus_dma_tag_t on success.
If this is the type of fix you were thinking of, I'll go ahead and
code something up for PCI devices.
* http://leaf.dragonflybsd.org/mailarchive/bugs/2004-10/msg00050.html
--
Chuck Tuffli
Agilent Technologies