gallium/docs: add more info about TXF and MSAA textures

If the texture is multisampled, the coord.w component indicates which
sample to fetch.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>

diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
index d7817cc9d0e767c45c6089ebc8b1de59f358269d..d1e7c88905e900729e24ea1460f6c3c4e2f7f55e 100644 (file)
--- a/src/gallium/docs/source/tgsi.rst
+++ b/src/gallium/docs/source/tgsi.rst
@@ -951,7 +951,9 @@ XXX doesn't look like most of the opcodes really belong here.
   image or PIPE_BUFFER resource. The source sampler may not be a CUBE or
   SHADOW.  src 0 is a
   four-component signed integer vector used to identify the single texel
-  accessed. 3 components + level.  Just like texture instructions, an optional
+  accessed. 3 components + level.  If the texture is multisampled, then
+  the fourth component indicates the sample, not the mipmap level.
+  Just like texture instructions, an optional
   offset vector is provided, which is subject to various driver restrictions
   (regarding range, source of offsets). This instruction ignores the sampler
   state.