[PATCH wayland] shm: add getters for the fd and offset

[Derek Foreman]

Sigh, realized this is still in patchwork and I never actually gave it a
proper look.

Sorry.

On 01/07/15 03:25 AM, Giulio Camuffo wrote:
> This allows to share the buffer data by mmapping the fd again.
> ---
>  src/wayland-server-core.h |  6 ++++++
>  src/wayland-shm.c         | 16 +++++++++++++++-
>  2 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/src/wayland-server-core.h b/src/wayland-server-core.h
> index 7d03789..938cdf7 100644
> --- a/src/wayland-server-core.h
> +++ b/src/wayland-server-core.h
> @@ -396,6 +396,12 @@ wl_shm_buffer_create(struct wl_client *client,
>  		     uint32_t id, int32_t width, int32_t height,
>  		     int32_t stride, uint32_t format);
>  
> +int
> +wl_shm_buffer_get_offset(struct wl_shm_buffer *buffer);
> +
> +int
> +wl_shm_buffer_get_fd(struct wl_shm_buffer *buffer);
> +
>  void wl_log_set_handler_server(wl_log_func_t handler);
>  
>  #ifdef  __cplusplus
> diff --git a/src/wayland-shm.c b/src/wayland-shm.c
> index b6b31d6..c85e839 100644
> --- a/src/wayland-shm.c
> +++ b/src/wayland-shm.c
> @@ -52,6 +52,7 @@ struct wl_shm_pool {
>  	int refcount;
>  	char *data;
>  	int32_t size;
> +	int fd;
>  };
>  
>  struct wl_shm_buffer {
> @@ -77,6 +78,7 @@ shm_pool_unref(struct wl_shm_pool *pool)
>  		return;
>  
>  	munmap(pool->data, pool->size);
> +	close(pool->fd);
>  	free(pool);
>  }
>  
> @@ -250,7 +252,7 @@ shm_create_pool(struct wl_client *client, struct wl_resource *resource,
>  				       "failed mmap fd %d", fd);
>  		goto err_close;
>  	}
> -	close(fd);
> +	pool->fd = fd;

I'm a little concerned that we now end up keeping an fd open for every
active shm_pool.  That could conceivably be every surface, subsurface,
and mouse cursor set an app is using?

Why do we need a second mapping?  Can't we just re-use the existing data
pointer?  (and do all the horrific refcounting required to make that
viable, I guess)


>  
>  	pool->resource =
>  		wl_resource_create(client, &wl_shm_pool_interface, 1, id);
> @@ -409,6 +411,18 @@ wl_shm_buffer_get_height(struct wl_shm_buffer *buffer)
>  	return buffer->height;
>  }

I guess we should have doxygen for the new APIs...

> +WL_EXPORT int
> +wl_shm_buffer_get_offset(struct wl_shm_buffer *buffer)
> +{
> +	return buffer->offset;
> +}
> +
> +WL_EXPORT int
> +wl_shm_buffer_get_fd(struct wl_shm_buffer *buffer)
> +{
> +	return buffer->pool->fd;
> +}
> +
>  static void
>  reraise_sigbus(void)
>  {
>