On Wed, 2009-08-26 at 15:20 -0500, Becky Bruce wrote:
> On Aug 26, 2009, at 9:08 AM, Michael Ellerman wrote:
>
> > On Wed, 2009-08-26 at 22:29 +1000, Benjamin Herrenschmidt wrote:
> >> On Mon, 2009-08-24 at 21:48 +0200, Christoph Hellwig wrote:
> >>> On Mon, Aug 24, 2009 at 11:17:14AM -0500, Becky Bruce wrote:
> >>>> Previously, this was specified as a void *, but that's not
> >>>> large enough on 32-bit systems with 36-bit physical
> >>>> addressing support. Change the type to dma_addr_t so it
> >>>> will scale based on the size of a dma address.
> >>>
> >>> This looks extreml ugly to me. It seems like the typical use is to
> >>> store a pointer to a structure. So what about making the direct
> >>> dma case follow that general scheme instead?
> >>>
> >>> E.g. declare a
> >>>
> >>> struct direct_dma_data {
> >>> dma_addr_t direct_dma_offset;
> >>> };
> >>>
> >>> and have one normal instace of it, and one per weird cell device.
> >>
> >> Right, but we want to avoid a structure for the classic case of 32-
> >> bit
> >> systems with no iommu...
> >>
> >> I wouldn't mind doing a union here.
> >
> > That might be best, the patch as it stands is a horrible mess of
> > casts.
>
> Let's be fair - the code before was a horrible mess of casts, I've
> just moved them :)Yeah true. Though I think we end up with more casts because there were more call sites using it as a pointer originally. But yeah it's not pretty either way. > > Stashing a dma_addr_t into a void * is sort of gross, but storing a > > pointer to some struct (a void *) in a dma_addr_t is _really_ gross :) > > Both are revolting (and storing a dma_addr_t into a void * is really > gross when the void * is smaller than the dma_addr_t!!). A union > might not be a bad idea, though. I'll look at doing that instead. Cool. That is how we're using it, sometimes it points to something sometimes it's a dma_addr_t, so I think a union will work. cheers
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