Re: [PATCH] dma-fence: Make ->enable_signaling optional

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 04-05-18 om 16:10 schreef Daniel Vetter:
> Many drivers have a trivial implementation for ->enable_signaling.
> Let's make it optional by assuming that signalling is already
> available when the callback isn't present.
>
> v2: Don't do the trick to set the ENABLE_SIGNAL_BIT
> unconditionally, it results in an expensive spinlock take for
> everyone. Instead just check if the callback is present. Suggested by
> Maarten.
>
> Also move misplaced kerneldoc hunk to the right patch.
>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Reviewed-by: Christian König <christian.koenig@amd.com> (v1)
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> Cc: Gustavo Padovan <gustavo@padovan.org>
> Cc: linux-media@vger.kernel.org
> Cc: linaro-mm-sig@lists.linaro.org
> ---
>  drivers/dma-buf/dma-fence.c | 9 +++++----
>  include/linux/dma-fence.h   | 3 ++-
>  2 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> index 4edb9fd3cf47..dd01a1720be9 100644
> --- a/drivers/dma-buf/dma-fence.c
> +++ b/drivers/dma-buf/dma-fence.c
> @@ -200,7 +200,8 @@ void dma_fence_enable_sw_signaling(struct dma_fence *fence)
>  
>  	if (!test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
>  			      &fence->flags) &&
> -	    !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
> +	    !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) &&
> +	    fence->ops->enable_signaling) {
>  		trace_dma_fence_enable_signal(fence);
>  
>  		spin_lock_irqsave(fence->lock, flags);
> @@ -260,7 +261,7 @@ int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb,
>  
>  	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
>  		ret = -ENOENT;
> -	else if (!was_set) {
> +	else if (!was_set && fence->ops->enable_signaling) {
>  		trace_dma_fence_enable_signal(fence);
>  
>  		if (!fence->ops->enable_signaling(fence)) {
> @@ -388,7 +389,7 @@ dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
>  	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
>  		goto out;
>  
> -	if (!was_set) {
> +	if (!was_set && fence->ops->enable_signaling) {
>  		trace_dma_fence_enable_signal(fence);
>  
>  		if (!fence->ops->enable_signaling(fence)) {
> @@ -560,7 +561,7 @@ dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
>  	       spinlock_t *lock, u64 context, unsigned seqno)
>  {
>  	BUG_ON(!lock);
> -	BUG_ON(!ops || !ops->wait || !ops->enable_signaling ||
> +	BUG_ON(!ops || !ops->wait ||
>  	       !ops->get_driver_name || !ops->get_timeline_name);
>  
>  	kref_init(&fence->refcount);
> diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> index 111aefe1c956..c053d19e1e24 100644
> --- a/include/linux/dma-fence.h
> +++ b/include/linux/dma-fence.h
> @@ -166,7 +166,8 @@ struct dma_fence_ops {
>  	 * released when the fence is signalled (through e.g. the interrupt
>  	 * handler).
>  	 *
> -	 * This callback is mandatory.
> +	 * This callback is optional. If this callback is not present, then the
> +	 * driver must always have signaling enabled.
>  	 */
>  	bool (*enable_signaling)(struct dma_fence *fence);
>  

Much better. :)

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>