[PATCH 04/15] dma-fence: Make ->wait callback optional - Linaro-mm-sig

3 May 2018

Almost everyone uses dma_fence_default_wait.
v2: Also remove the BUG_ON(!ops->wait) (Chris).
Reviewed-by: Christian König christian.koenig@amd.com (v1)
Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch
Cc: Chris Wilson chris@chris-wilson.co.uk
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-array.c |  1 -
 drivers/dma-buf/dma-fence.c       |  8 +++++---
 drivers/dma-buf/sw_sync.c         |  1 -
 include/linux/dma-fence.h         | 13 ++++++++-----
 4 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c
index dd1edfb27b61..a8c254497251 100644
--- a/drivers/dma-buf/dma-fence-array.c
+++ b/drivers/dma-buf/dma-fence-array.c
@@ -104,7 +104,6 @@ const struct dma_fence_ops dma_fence_array_ops = {
    .get_timeline_name = dma_fence_array_get_timeline_name,
    .enable_signaling = dma_fence_array_enable_signaling,
    .signaled = dma_fence_array_signaled,
-	.wait = dma_fence_default_wait,
    .release = dma_fence_array_release,
 };
 EXPORT_SYMBOL(dma_fence_array_ops);
diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 59049375bd19..41ec19c9efc7 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -158,7 +158,10 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
    	return -EINVAL;
trace_dma_fence_wait_start(fence);
-	ret = fence->ops->wait(fence, intr, timeout);
+	if (fence->ops->wait)
+		ret = fence->ops->wait(fence, intr, timeout);
+	else
+		ret = dma_fence_default_wait(fence, intr, timeout);
    trace_dma_fence_wait_end(fence);
    return ret;
 }
@@ -562,8 +565,7 @@ 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->get_driver_name || !ops->get_timeline_name);
+	BUG_ON(!ops || !ops->get_driver_name || !ops->get_timeline_name);
kref_init(&fence->refcount);
    fence->ops = ops;
diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c
index 3d78ca89a605..53c1d6d36a64 100644
--- a/drivers/dma-buf/sw_sync.c
+++ b/drivers/dma-buf/sw_sync.c
@@ -188,7 +188,6 @@ static const struct dma_fence_ops timeline_fence_ops = {
    .get_timeline_name = timeline_fence_get_timeline_name,
    .enable_signaling = timeline_fence_enable_signaling,
    .signaled = timeline_fence_signaled,
-	.wait = dma_fence_default_wait,
    .release = timeline_fence_release,
    .fence_value_str = timeline_fence_value_str,
    .timeline_value_str = timeline_fence_timeline_value_str,
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index c053d19e1e24..02dba8cd033d 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -191,11 +191,14 @@ struct dma_fence_ops {
    /**
     * @wait:
     *
-	 * Custom wait implementation, or dma_fence_default_wait.
+	 * Custom wait implementation, defaults to dma_fence_default_wait() if
+	 * not set.
     *
-	 * Must not be NULL, set to dma_fence_default_wait for default implementation.
-	 * the dma_fence_default_wait implementation should work for any fence, as long
-	 * as enable_signaling works correctly.
+	 * 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.
     *
     * 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
@@ -203,7 +206,7 @@ struct dma_fence_ops {
     * which should be treated as if the fence is signaled. For example a hardware
     * lockup could be reported like that.
     *
-	 * This callback is mandatory.
+	 * This callback is optional.
     */
    signed long (*wait)(struct dma_fence *fence,
    		    bool intr, signed long timeout);
-- 
2.17.0


    