gallium: add PIPE_CAP_INVALIDATE_BUFFER

It makes sense to re-use pipe->invalidate_resource for the purpose of
glInvalidateBufferData, but this function is already implemented in vc4
where it doesn't have the expected behavior. So add a capability flag
to indicate that the driver supports the expected behavior.

Reviewed-by: Marek Olšák <[email protected]>

2 files changed, 7 insertions, 2 deletions

diff --git a/src/gallium/include/pipe/p_context.h b/src/gallium/include/pipe/p_context.h
index be7447de67d..78155c05348 100644
--- a/src/gallium/include/pipe/p_context.h
+++ b/src/gallium/include/pipe/p_context.h
@@ -649,11 +649,15 @@ struct pipe_context {
                           struct pipe_resource *resource);
 
    /**
-    * Invalidate the contents of the resource.
+    * Invalidate the contents of the resource. This is used to
     *
-    * This is used to implement EGL's semantic of undefined depth/stencil
+    * (1) implement EGL's semantic of undefined depth/stencil
     * contenst after a swapbuffers.  This allows a tiled renderer (for
     * example) to not store the depth buffer.
+    *
+    * (2) implement GL's InvalidateBufferData. For backwards compatibility,
+    * you must only rely on the usability for this purpose when
+    * PIPE_CAP_INVALIDATE_BUFFER is enabled.
     */
    void (*invalidate_resource)(struct pipe_context *ctx,
                                struct pipe_resource *resource);
diff --git a/src/gallium/include/pipe/p_defines.h b/src/gallium/include/pipe/p_defines.h
index dd76fe553e4..0655f080e42 100644
--- a/src/gallium/include/pipe/p_defines.h
+++ b/src/gallium/include/pipe/p_defines.h
@@ -642,6 +642,7 @@ enum pipe_cap
    PIPE_CAP_TGSI_FS_POSITION_IS_SYSVAL,
    PIPE_CAP_TGSI_FS_FACE_IS_INTEGER_SYSVAL,
    PIPE_CAP_SHADER_BUFFER_OFFSET_ALIGNMENT,
+   PIPE_CAP_INVALIDATE_BUFFER,
 };
 
 #define PIPE_QUIRK_TEXTURE_BORDER_COLOR_SWIZZLE_NV50 (1 << 0)