On Wed, Jul 21, 2021 at 11:21:32AM +0200, Christian König wrote:
> This callback is pretty much deprecated and should not be used by new implementations.
>
> Clarify that in the documentation as well.
>
> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> ---
> include/linux/dma-fence.h | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> index 6ffb4b2c6371..a44e42b86c2a 100644
> --- a/include/linux/dma-fence.h
> +++ b/include/linux/dma-fence.h
> @@ -214,19 +214,15 @@ struct dma_fence_ops {
> * Custom wait implementation, defaults to dma_fence_default_wait() if
> * not set.
> *
> - * The dma_fence_default_wait implementation should work for any fence, as long
> - * as @enable_signaling works correctly. This hook allows drivers to
> - * have an optimized version for the case where a process context is
> - * already available, e.g. if @enable_signaling for the general case
> - * needs to set up a worker thread.
> + * Deprecated and should not be used by new implementations. Only used
> + * by existing implementations which need special handling for their
> + * hardware reset procedure.
I thought the other reason was unreliable interrupts, so waiters had to
wake up once per jiffy? So maybe: "... for their hw reset procedure or for
handling missed interrupts".
Maybe also add here:
New implementations must have an @enable_signalling and dma_fence_signal()
implementation which does not require special handling to make
dma_fence_wait() work.
With these:
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> *
> * Must return -ERESTARTSYS if the wait is intr = true and the wait was
> * interrupted, and remaining jiffies if fence has signaled, or 0 if wait
> * timed out. Can also return other error values on custom implementations,
> * which should be treated as if the fence is signaled. For example a hardware
> * lockup could be reported like that.
> - *
> - * This callback is optional.
> */
> signed long (*wait)(struct dma_fence *fence,
> bool intr, signed long timeout);
> --
> 2.25.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
