docs/gallium: Explain that MSAA transfer_map must be supported.

It's called this way in various drivers, and is an established part of the
transfer_map interface.

Reviewed-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20523>
This commit is contained in:
Emma Anholt
2023-01-04 09:11:19 -08:00
committed by Marge Bot
parent 03a26ae3d9
commit 95c4241f47

View File

@@ -699,6 +699,11 @@ the box region, not the beginning of the resource. If transfer_map fails,
the returned pointer to the buffer memory is NULL, and the pointer
to the transfer object remains unchanged (i.e. it can be non-NULL).
When mapping an MSAA surface, the samples are implicitly resolved to
single-sampled for reads (returning the first sample for depth/stencil/integer,
averaged for others). See u_transfer_helper's U_TRANSFER_HELPER_MSAA_MAP for a
way to get that behavior using a resolve blit.
``transfer_unmap`` remove the memory mapping for and destroy
the transfer object. The pointer into the resource should be considered
invalid and discarded.