[Mesa-dev] [RFC PATCH] mesa: add support for multiple buffer mappings

[Marek Olšák]

From: Marek Olšák <marek.olsak at amd.com>

OpenGL allows a buffer to be mapped only once, but we also map buffers
internally, e.g. in the software primitive restart fallback, for PBOs,
vbo_get_minmax_index, etc. This has always been a problem, but it will
be a bigger problem with persistent buffer mappings, which will prevent
all Mesa functions from mapping buffers for internal purposes.

This adds a driver inteface to core Mesa which supports multiple buffer
mappings and allows 2 mappings: one for the GL user and one for Mesa.

Note that Gallium supports an unlimited number of buffer and texture
mappings, so it's not really an issue for Gallium.

This is just the interface change. Please review. If you don't like it,
feel free to propose how you would do it. Thank you.

---
 src/mesa/main/dd.h     |  9 ++++++---
 src/mesa/main/mtypes.h | 25 ++++++++++++++++++-------
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/src/mesa/main/dd.h b/src/mesa/main/dd.h
index ab135f4..fdd0d94 100644
--- a/src/mesa/main/dd.h
+++ b/src/mesa/main/dd.h
@@ -598,14 +598,17 @@ struct dd_function_table {
     */
    void * (*MapBufferRange)( struct gl_context *ctx, GLintptr offset,
                              GLsizeiptr length, GLbitfield access,
-                             struct gl_buffer_object *obj);
+                             struct gl_buffer_object *obj,
+                             enum gl_map_buffer_index index);
 
    void (*FlushMappedBufferRange)(struct gl_context *ctx,
                                   GLintptr offset, GLsizeiptr length,
-                                  struct gl_buffer_object *obj);
+                                  struct gl_buffer_object *obj,
+                                  enum gl_map_buffer_index index);
 
    GLboolean (*UnmapBuffer)( struct gl_context *ctx,
-			     struct gl_buffer_object *obj );
+			     struct gl_buffer_object *obj,
+                             enum gl_map_buffer_index index);
    /*@}*/
 
    /**
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 4aaad16..5200377 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -1437,6 +1437,22 @@ struct gl_viewport_attrib
    GLmatrix _WindowMap;		/**< Mapping transformation as a matrix. */
 };
 
+enum gl_map_buffer_index {
+   MAP_CTX_USER,
+   MAP_CTX_INTERNAL,
+
+   NUM_MAP_BUFFER_CONTEXTS
+};
+
+/**
+ * Fields describing a mapped buffer range.
+ */
+struct gl_map_buffer_context {
+   GLbitfield AccessFlags; /**< Mask of GL_MAP_x_BIT flags */
+   GLvoid *Pointer;     /**< User-space address of mapping */
+   GLintptr Offset;     /**< Mapped offset */
+   GLsizeiptr Length;   /**< Mapped length */
+};
 
 /**
  * GL_ARB_vertex/pixel_buffer_object buffer object
@@ -1451,17 +1467,12 @@ struct gl_buffer_object
    GLbitfield StorageFlags; /**< GL_MAP_PERSISTENT_BIT, etc. */
    GLsizeiptrARB Size;  /**< Size of buffer storage in bytes */
    GLubyte *Data;       /**< Location of storage either in RAM or VRAM. */
-   /** Fields describing a mapped buffer */
-   /*@{*/
-   GLbitfield AccessFlags; /**< Mask of GL_MAP_x_BIT flags */
-   GLvoid *Pointer;     /**< User-space address of mapping */
-   GLintptr Offset;     /**< Mapped offset */
-   GLsizeiptr Length;   /**< Mapped length */
-   /*@}*/
    GLboolean DeletePending;   /**< true if buffer object is removed from the hash */
    GLboolean Written;   /**< Ever written to? (for debugging) */
    GLboolean Purgeable; /**< Is the buffer purgeable under memory pressure? */
    GLboolean Immutable; /**< GL_ARB_buffer_storage */
+
+   struct gl_map_buffer_context Mappings[NUM_MAP_BUFFER_CONTEXTS];
 };
 
 
-- 
1.8.3.2