Subject: Re: bus_dmamem question
To: None <firstname.lastname@example.org>
From: Izumi Tsutsui <email@example.com>
Date: 03/02/2006 22:11:29
In article <firstname.lastname@example.org>
> > Are you really expecting a physical address here, or is this some
> > convenient way to get at a single bus-dma opaque cookie, in an
> > already-existing dma_map, corresponding to the given kva?
> Yes, it is just for convenience. The function should return the physical
> address relative to the parenting PCI bus, which the hardware is on, which
> should be programmed into the hardware.
Not all architectures use the physical address for DMA address
to be programmed into the hardware, so the name of *_vtophys()
is not appropriate.
(See Jason's bus_dma paper in src/share/doc/papers/bus_dma/)