[PATCH 01/10] drm/amdgpu: introduce amdgpu_lookup_queue_by_doorbell

[Zhu Lingshan <lingshan.zhu@amd.com>]

This commit introduces a new helper
amdgpu_lookup_queue_by_doorbell which helps
look up a user queue with the given doorbell id
in a xarray.

This function takes a kref of the user space queue.

Signed-off-by: Zhu Lingshan <lingshan.zhu@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c | 30 +++++++++++++++++++++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h |  2 ++
 2 files changed, 32 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
index 0a816b3c5ff9..e0639f844a8e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
@@ -609,6 +609,36 @@ struct amdgpu_usermode_queue *amdgpu_userq_get(struct amdgpu_userq_mgr *uq_mgr,
 	return queue;
 }
 
+/**
+ * amdgpu_lookup_queue_by_doorbell - look up a user queue by doorbell
+ * @xa: user queue XArray indexed by doorbell
+ * @doorbell: doorbell index
+ *
+ * Return: A queue with the doorbell indexed, or NULL if no such a queue found.
+ *
+ * This function increases kref of the queue, the caller
+ * must release the reference with amdgpu_userq_put().
+ */
+struct amdgpu_usermode_queue *
+amdgpu_lookup_queue_by_doorbell(struct xarray *xa, u32 doorbell)
+{
+	struct amdgpu_usermode_queue *queue;
+	unsigned long flags;
+
+	xa_lock_irqsave(xa, flags);
+	queue = xa_load(xa, doorbell);
+	if (!queue)
+		goto out_unlock;
+
+	if (!kref_get_unless_zero(&queue->refcount))
+		queue = NULL;
+
+out_unlock:
+	xa_unlock_irqrestore(xa, flags);
+
+	return queue;
+}
+
 void amdgpu_userq_put(struct amdgpu_usermode_queue *queue)
 {
 	if (queue)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h
index 6412a7f7b6ef..8fc73862f64e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h
@@ -151,6 +151,8 @@ struct amdgpu_db_info {
 };
 
 struct amdgpu_usermode_queue *amdgpu_userq_get(struct amdgpu_userq_mgr *uq_mgr, u32 qid);
+struct amdgpu_usermode_queue *
+amdgpu_lookup_queue_by_doorbell(struct xarray *xa, u32 doorbell);
 void amdgpu_userq_put(struct amdgpu_usermode_queue *queue);
 
 int amdgpu_userq_ioctl(struct drm_device *dev, void *data, struct drm_file *filp);
-- 
2.53.0