On Thu, 2009-10-01 at 16:16 +0100, José Fonseca wrote:
> On Thu, 2009-10-01 at 07:44 -0700, Michel Dänzer wrote:
> > From: Michel Dänzer <daen...@vmware.com>
> >
> > Asks the driver to map the texture storage directly or return NULL if that's
> > not possible.
> > ---
> > src/gallium/include/pipe/p_defines.h | 13 ++++++++++++-
> > 1 files changed, 12 insertions(+), 1 deletions(-)
> >
> > diff --git a/src/gallium/include/pipe/p_defines.h
> > b/src/gallium/include/pipe/p_defines.h
> > index ad42bef..f8fa1e3 100644
> > --- a/src/gallium/include/pipe/p_defines.h
> > +++ b/src/gallium/include/pipe/p_defines.h
> > @@ -193,7 +193,18 @@ enum pipe_texture_target {
> > enum pipe_transfer_usage {
> > PIPE_TRANSFER_READ = (1 << 0),
> > PIPE_TRANSFER_WRITE = (1 << 1),
> > - PIPE_TRANSFER_READ_WRITE = PIPE_TRANSFER_READ | PIPE_TRANSFER_WRITE
> > /**< Read/modify/write */
> > + /** Read/modify/write */
> > + PIPE_TRANSFER_READ_WRITE = PIPE_TRANSFER_READ | PIPE_TRANSFER_WRITE,
> > + /**
> > + * The transfer should map the texture storage directly. The driver may
> > + * return NULL if that isn't possible, and the state tracker needs to
> > cope
> > + * with that and use an alternative path without this flag.
> > + *
> > + * E.g. the state tracker could have a simpler path which maps textures
> > and
> > + * does read/modify/write cycles on them directly, and a more
> > complicated
> > + * path which uses minimal read and write transfers.
> > + */
> > + PIPE_TRANSFER_MAP_DIRECTLY = (1 << 2)
> > };
>
> Michel,
>
> To help understand, could you give a concrete example of the "simpler
> path" and "complicated path"?
See patch 3, and the EXA 'mixed pixmaps' code in xserver >= 1.7. The
Xorg state tracker uses PIPE_TRANSFER_MAP_DIRECTLY in the EXA
PrepareAccess hook, as the EXA Prepare/FinishAccess hooks intend a
direct mapping. If the Gallium driver returns NULL, the Xorg state
tracker propagates that to EXA, which in turn uses the
DownloadFrom/UploadToScreen hooks for minimal transfers (with some
damage tracking overhead).
--
Earthling Michel Dänzer | http://www.vmware.com
Libre software enthusiast | Debian, X and DRI developer
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