Re: [RFC 2/8] dma-buf/sync_file: add sync_file_fences_get()

[Daniel Vetter]

On Thu, Apr 14, 2016 at 06:29:35PM -0700, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> 
> Creates a function that given an sync file descriptor returns a
> fence_collection containing all fences in the sync_file.
> 
> If there is only one fence in the sync_file this fence itself is returned,
> however if there is more than one, a fence_collection fence is returned.
> 
> Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> ---
>  drivers/dma-buf/sync_file.c | 37 +++++++++++++++++++++++++++++++++++++
>  include/linux/sync_file.h   | 10 ++++++++++
>  2 files changed, 47 insertions(+)
> 
> diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
> index 4d2af24..926fafa 100644
> --- a/drivers/dma-buf/sync_file.c
> +++ b/drivers/dma-buf/sync_file.c
> @@ -23,6 +23,7 @@
>  #include <linux/slab.h>
>  #include <linux/uaccess.h>
>  #include <linux/anon_inodes.h>
> +#include <linux/fence-collection.h>
>  #include <linux/sync_file.h>
>  #include <uapi/linux/sync_file.h>
>  
> @@ -122,6 +123,39 @@ void sync_file_install(struct sync_file *sync_file, int fd)
>  }
>  EXPORT_SYMBOL(sync_file_install);
>  
> +struct fence *sync_file_fences_get(int fd)
> +{
> +	struct sync_file *sync_file;
> +	struct fence_collection *collection;
> +	int i;
> +
> +	sync_file = sync_file_fdget(fd);
> +	if (!sync_file)
> +		return NULL;
> +
> +	if (sync_file->num_fences == 1) {
> +		struct fence *fence = sync_file->cbs[0].fence;
> +
> +		sync_file_put(sync_file);
> +		return fence;
> +	}
> +
> +	collection = fence_collection_init(sync_file->num_fences);
> +	if (!collection) {
> +		sync_file_put(sync_file);
> +		return NULL;
> +	}
> +
> +	for (i = 0 ; i < sync_file->num_fences ; i++)
> +		fence_collection_add(collection, sync_file->cbs[i].fence);
> +
> +	sync_file->collection = collection;
> +	sync_file_put(sync_file);
> +
> +	return &collection->base;
> +}

This function should probably acquire a reference for the returned fence
for the caller.
-Daniel

> +EXPORT_SYMBOL(sync_file_fences_get);
> +
>  static void sync_file_add_pt(struct sync_file *sync_file, int *i,
>  			     struct fence *fence)
>  {
> @@ -200,6 +234,9 @@ static void sync_file_free(struct kref *kref)
>  						     kref);
>  	int i;
>  
> +	if (sync_file->collection)
> +		fence_collection_put(sync_file->collection);
> +
>  	for (i = 0; i < sync_file->num_fences; ++i) {
>  		fence_remove_callback(sync_file->cbs[i].fence,
>  				      &sync_file->cbs[i].cb);
> diff --git a/include/linux/sync_file.h b/include/linux/sync_file.h
> index 7b7a89d..2cb0486 100644
> --- a/include/linux/sync_file.h
> +++ b/include/linux/sync_file.h
> @@ -49,6 +49,7 @@ struct sync_file {
>  	wait_queue_head_t	wq;
>  	atomic_t		status;
>  
> +	struct fence_collection *collection;
>  	struct sync_file_cb	cbs[];
>  };
>  
> @@ -103,4 +104,13 @@ void sync_file_put(struct sync_file *sync_file);
>   */
>  void sync_file_install(struct sync_file *sync_file, int fd);
>  
> +/**
> + * sync_file_fences_get - get the fence related to the fd
> + * @fd:		file descriptor to look for a fence collection
> + *
> + * Ensures @fd references a valid sync_file and returns the base object
> + * of the fence_collection that contains all fences in the sync_file
> + * or NULL in case of error.
> + */
> +struct fence *sync_file_fences_get(int fd);
>  #endif /* _LINUX_SYNC_H */
> -- 
> 2.5.5
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch