On 10/2/07, James Bottomley <James.Bottomley@xxxxxxxxxxxx> wrote:
> On Mon, 2007-10-01 at 21:22 -0700, Greg KH wrote:
> > On Mon, Oct 01, 2007 at 07:39:02PM -0600, Matthew Wilcox wrote:
> > > On Mon, Oct 01, 2007 at 07:36:10PM -0400, James Bottomley wrote:
> > > > One possibility we could do is to add a
> > > >
> > > > struct dma_device {
> > > > struct device dev;
> > > > u64 dma_mask;
> > > > u64 coherent_dma_mask;
> > > > unsigned int max_segment_size;
> > > > /* plus any other DMA parameters */
> > > > };
> > > >
> > > > but then every bus that can do DMA would need to include a struct
> > > > dma_device instead of the struct device they do now. Then the IOMMU
> > > > would know it could cast out from struct device to struct dma_device,
> > > > but this would be a lot of work to thread through the current
> > > > infrastructure.
> >
> > Why not just hang these fields off of a struct device, that way if the
> > device doesn't/can't do dma, it only has the "loss" of a single pointer,
> > not all of these fields?
>
> Well, that's just a bit ugly ... I assume you're thinking of adding a
> struct device_dma_parameters, and then defining the platform device as
>
> struct pci_dev {
> ...
> struct device dev;
> struct device_dma_parameters dma_parms;
> ...
> };
>
> and then setting up the pointer?
I guess Greg means:
struct device {
...
struct device_dma_parameters *dma_parms;
}
and allocate dma_parms on demand.
Kay
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