Some driver use fence->ops to test if a fence was initialized or not.
The problem is that this utilizes internal behavior of the dma_fence
implementation.

So better abstract that into a function.

Signed-off-by: Christian König <[email protected]>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_job.c | 13 +++++++------
 drivers/gpu/drm/qxl/qxl_release.c       |  2 +-
 include/linux/dma-fence.h               | 12 ++++++++++++
 3 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
index 0a0dcbf0798d..b97f90bbe8b9 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
@@ -278,9 +278,10 @@ void amdgpu_job_free_resources(struct amdgpu_job *job)
        unsigned i;
 
        /* Check if any fences were initialized */
-       if (job->base.s_fence && job->base.s_fence->finished.ops)
+       if (job->base.s_fence &&
+           dma_fence_is_initialized(&job->base.s_fence->finished))
                f = &job->base.s_fence->finished;
-       else if (job->hw_fence && job->hw_fence->base.ops)
+       else if (dma_fence_is_initialized(&job->hw_fence->base))
                f = &job->hw_fence->base;
        else
                f = NULL;
@@ -297,11 +298,11 @@ static void amdgpu_job_free_cb(struct drm_sched_job 
*s_job)
 
        amdgpu_sync_free(&job->explicit_sync);
 
-       if (job->hw_fence->base.ops)
+       if (dma_fence_is_initialized(&job->hw_fence->base))
                dma_fence_put(&job->hw_fence->base);
        else
                kfree(job->hw_fence);
-       if (job->hw_vm_fence->base.ops)
+       if (dma_fence_is_initialized(&job->hw_vm_fence->base))
                dma_fence_put(&job->hw_vm_fence->base);
        else
                kfree(job->hw_vm_fence);
@@ -335,11 +336,11 @@ void amdgpu_job_free(struct amdgpu_job *job)
        if (job->gang_submit != &job->base.s_fence->scheduled)
                dma_fence_put(job->gang_submit);
 
-       if (job->hw_fence->base.ops)
+       if (dma_fence_is_initialized(&job->hw_fence->base))
                dma_fence_put(&job->hw_fence->base);
        else
                kfree(job->hw_fence);
-       if (job->hw_vm_fence->base.ops)
+       if (dma_fence_is_initialized(&job->hw_vm_fence->base))
                dma_fence_put(&job->hw_vm_fence->base);
        else
                kfree(job->hw_vm_fence);
diff --git a/drivers/gpu/drm/qxl/qxl_release.c 
b/drivers/gpu/drm/qxl/qxl_release.c
index 7b3c9a6016db..b38ae0b25f3c 100644
--- a/drivers/gpu/drm/qxl/qxl_release.c
+++ b/drivers/gpu/drm/qxl/qxl_release.c
@@ -146,7 +146,7 @@ qxl_release_free(struct qxl_device *qdev,
        idr_remove(&qdev->release_idr, release->id);
        spin_unlock(&qdev->release_idr_lock);
 
-       if (release->base.ops) {
+       if (dma_fence_is_initialized(&release->base)) {
                WARN_ON(list_empty(&release->bos));
                qxl_release_free_list(release);
 
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index eea674acdfa6..371aa8ecf18e 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -274,6 +274,18 @@ void dma_fence_release(struct kref *kref);
 void dma_fence_free(struct dma_fence *fence);
 void dma_fence_describe(struct dma_fence *fence, struct seq_file *seq);
 
+/**
+ * dma_fence_is_initialized - test if fence was initialized
+ * @fence: fence to test
+ *
+ * Return: True if fence was initialized, false otherwise. Works correctly only
+ * when memory backing the fence structure is zero initialized on allocation.
+ */
+static inline bool dma_fence_is_initialized(struct dma_fence *fence)
+{
+       return fence && !!fence->ops;
+}
+
 /**
  * dma_fence_put - decreases refcount of the fence
  * @fence: fence to reduce refcount of
-- 
2.43.0

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