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

[Ian Romanick]

On 02/05/2014 02:06 PM, Marek Olšák wrote:
> 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.

This seems like a reasonable enough interface to me.  If we decide that
it's insufficient or ugly later, it should be easy enough to change.  I
also like Eric's and Brian's suggestions.

> ---
>  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];
>  };
>  
>