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

[Brian Paul]

On 02/05/2014 03:06 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.
>
> ---
>   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
> +};

We've been doing typedefs for the enums in mtypes.h and I'd probably use 
shorter names.  Maybe this:

typedef enum
{
    MAP_USER,
    MAP_INTERNAL,
    MAP_BUFFER_COUNT;
} gl_map_buffer_index;



> +
> +/**
> + * 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 */
> +};

I agree with Eric's naming suggestion here.

Otherwise, this looks OK to me, though I haven't really thought it 
through very much.

-Brian