[Mesa-dev] [PATCH 2/6] dri: extend fence extension to support native fd fences

[Marek Olšák]

On Fri, Apr 1, 2016 at 10:29 PM, Rob Clark <robdclark at gmail.com> wrote:
> From: Rob Clark <robclark at freedesktop.org>
>
> Required to implement EGL_ANDROID_native_fence_sync.
>
> Signed-off-by: Rob Clark <robclark at freedesktop.org>
> ---
>  include/GL/internal/dri_interface.h | 44 ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 43 insertions(+), 1 deletion(-)
>
> diff --git a/include/GL/internal/dri_interface.h b/include/GL/internal/dri_interface.h
> index 2b49a29..8b0dadc 100644
> --- a/include/GL/internal/dri_interface.h
> +++ b/include/GL/internal/dri_interface.h
> @@ -339,12 +339,19 @@ struct __DRI2throttleExtensionRec {
>   */
>
>  #define __DRI2_FENCE "DRI2_Fence"
> -#define __DRI2_FENCE_VERSION 1
> +#define __DRI2_FENCE_VERSION 2
>
>  #define __DRI2_FENCE_TIMEOUT_INFINITE     0xffffffffffffffffllu
>
>  #define __DRI2_FENCE_FLAG_FLUSH_COMMANDS  (1 << 0)
>
> +/**
> + * \name Capabilities that might be returned by __DRI2fenceExtensionRec::get_capabilities
> + */
> +/*@{*/
> +#define __DRI_FENCE_CAP_NATIVE_FD 1
> +/*@}*/
> +
>  struct __DRI2fenceExtensionRec {
>     __DRIextension base;
>
> @@ -389,6 +396,41 @@ struct __DRI2fenceExtensionRec {
>      *                sense with this function (right now there are none)
>      */
>     void (*server_wait_sync)(__DRIcontext *ctx, void *fence, unsigned flags);
> +
> +   /**
> +    * Query for general capabilities of the driver that concern fences.
> +    * Returns a bitmask of __DRI_FENCE_CAP_x
> +    *
> +    * \since 2
> +    */
> +   unsigned (*get_capabilities)(__DRIscreen *screen);
> +
> +   /**
> +    * Create an fd (file descriptor) associated fence.  If the fence fd
> +    * is -1, this behaves similarly to create_fence() except that when
> +    * rendering is flushed the driver creates a fence fd.  Otherwise,
> +    * the driver wraps an existing fence fd.
> +    *
> +    * This is used to implement the EGL_ANDROID_native_fence_sync extension.
> +    *
> +    * \since 2
> +    *
> +    * \param ctx     the context associated with the fence
> +    * \param fd      the fence fd or -1
> +    */
> +   void *(*create_fence_fd)(__DRIcontext *ctx, int fd);
> +
> +   /**
> +    * For fences created with create_fence_fd(), after rendering is flushed,
> +    * this retrieves the native fence fd.  Caller takes ownership of the
> +    * fd and will close() it when it is no longer needed.
> +    *
> +    * \since 2
> +    *
> +    * \param screen  the screen associated with the fence
> +    * \param fence   the fence
> +    */
> +   int (*get_fence_fd)(__DRIscreen *screen, void *fence);

This can be even more generic. If you add a requirement that
get_fence_fd must work with any fence, create_fence_fd() essentially
becomes import_fence_fd() and create_fence() can be used if fd is -1.

The reason is that we may be interested in adding support for
cl_khr_gl_event in the future (MesaGL + HSA/OpenCL), which allows
sharing any GL fence with CL, and we will most likely use fd fences.

Marek