Mesa (master): virgl: More info about chosen alignment value

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Module: Mesa
Branch: master
Commit: 8089d3658ad3a2d62fb815d545b727bb72ed63c9
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=8089d3658ad3a2d62fb815d545b727bb72ed63c9

Author: Alexandros Frantzis <alexandros.frantzis at collabora.com>
Date:   Thu May 23 14:58:46 2019 +0300

virgl: More info about chosen alignment value

Add more info about why the value of VIRGL_MAP_BUFFER_ALIGNMENT.

Signed-off-by: Alexandros Frantzis <alexandros.frantzis at collabora.com>
Reviewed-by: Chia-I Wu <olvaffe at gmail.com>

---

 src/gallium/drivers/virgl/virgl_screen.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/gallium/drivers/virgl/virgl_screen.h b/src/gallium/drivers/virgl/virgl_screen.h
index 0256d471f22..93b52b5138d 100644
--- a/src/gallium/drivers/virgl/virgl_screen.h
+++ b/src/gallium/drivers/virgl/virgl_screen.h
@@ -58,6 +58,11 @@ virgl_screen(struct pipe_screen *pipe)
 boolean
 virgl_has_readback_format(struct pipe_screen *screen, enum virgl_formats fmt);
 
+/* GL_ARB_map_buffer_alignment requires 64 as the minimum alignment value.  In
+ * addition to complying with the extension, a high enough alignment value is
+ * expected by various external GL clients. For example, wined3d doesn't like
+ * maps that don't have a 16 byte alignment.
+ */
 #define VIRGL_MAP_BUFFER_ALIGNMENT 64
 
 #endif