staging: vchiq_core: Simplify vchiq_bulk_transfer()

Factor out core logic for preparing bulk data transfer(mutex locking,
waits on vchiq_bulk_queue wait-queue, initialising the bulk transfer)
out of the vchiq_bulk_transfer(). This simplifies the existing
vchiq_bulk_transfer() and makes it more readable since all the core
logic is handled in vchiq_bulk_xfer_queue_msg_interruptible(). It
will also help us to refactor vchiq_bulk_transfer() easily for different
vchiq bulk transfer modes.

No functional changes intended in this patch.
Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
Tested-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://lore.kernel.org/r/20240910051007.297227-3-umang.jain@ideasonboard.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c

@@ -2655,6 +2655,116 @@ close_service_complete(struct vchiq_service *service, int failstate)
 	return status;
 }
 
+/*
+ * Prepares a bulk transfer to be queued. The function is interruptible and is
+ * intended to be called from user threads. It may return -EAGAIN to indicate
+ * that a signal has been received and the call should be retried after being
+ * returned to user context.
+ */
+static int
+vchiq_bulk_xfer_queue_msg_interruptible(struct vchiq_service *service,
+					void *offset, void __user *uoffset,
+					int size, void *userdata,
+					enum vchiq_bulk_mode mode,
+					enum vchiq_bulk_dir dir)
+{
+	struct vchiq_bulk_queue *queue;
+	struct vchiq_bulk *bulk;
+	struct vchiq_state *state = service->state;
+	const char dir_char = (dir == VCHIQ_BULK_TRANSMIT) ? 't' : 'r';
+	const int dir_msgtype = (dir == VCHIQ_BULK_TRANSMIT) ?
+		VCHIQ_MSG_BULK_TX : VCHIQ_MSG_BULK_RX;
+	int status = -EINVAL;
+	int payload[2];
+
+	queue = (dir == VCHIQ_BULK_TRANSMIT) ?
+		&service->bulk_tx : &service->bulk_rx;
+
+	if (mutex_lock_killable(&service->bulk_mutex))
+		return -EAGAIN;
+
+	if (queue->local_insert == queue->remove + VCHIQ_NUM_SERVICE_BULKS) {
+		VCHIQ_SERVICE_STATS_INC(service, bulk_stalls);
+		do {
+			mutex_unlock(&service->bulk_mutex);
+			if (wait_for_completion_interruptible(&service->bulk_remove_event))
+				return -EAGAIN;
+			if (mutex_lock_killable(&service->bulk_mutex))
+				return -EAGAIN;
+		} while (queue->local_insert == queue->remove +
+				VCHIQ_NUM_SERVICE_BULKS);
+	}
+
+	bulk = &queue->bulks[BULK_INDEX(queue->local_insert)];
+
+	bulk->mode = mode;
+	bulk->dir = dir;
+	bulk->userdata = userdata;
+	bulk->size = size;
+	bulk->actual = VCHIQ_BULK_ACTUAL_ABORTED;
+
+	if (vchiq_prepare_bulk_data(service->instance, bulk, offset, uoffset, size, dir))
+		goto unlock_error_exit;
+
+	/*
+	 * Ensure that the bulk data record is visible to the peer
+	 * before proceeding.
+	 */
+	wmb();
+
+	dev_dbg(state->dev, "core: %d: bt (%d->%d) %cx %x@%pad %pK\n",
+		state->id, service->localport, service->remoteport,
+		dir_char, size, &bulk->data, userdata);
+
+	/*
+	 * The slot mutex must be held when the service is being closed, so
+	 * claim it here to ensure that isn't happening
+	 */
+	if (mutex_lock_killable(&state->slot_mutex)) {
+		status = -EAGAIN;
+		goto cancel_bulk_error_exit;
+	}
+
+	if (service->srvstate != VCHIQ_SRVSTATE_OPEN)
+		goto unlock_both_error_exit;
+
+	payload[0] = lower_32_bits(bulk->data);
+	payload[1] = bulk->size;
+	status = queue_message(state,
+			       NULL,
+			       VCHIQ_MAKE_MSG(dir_msgtype,
+					      service->localport,
+					      service->remoteport),
+			       memcpy_copy_callback,
+			       &payload,
+			       sizeof(payload),
+			       QMFLAGS_IS_BLOCKING |
+			       QMFLAGS_NO_MUTEX_LOCK |
+			       QMFLAGS_NO_MUTEX_UNLOCK);
+	if (status)
+		goto unlock_both_error_exit;
+
+	queue->local_insert++;
+
+	mutex_unlock(&state->slot_mutex);
+	mutex_unlock(&service->bulk_mutex);
+
+	dev_dbg(state->dev, "core: %d: bt:%d %cx li=%x ri=%x p=%x\n",
+		state->id, service->localport, dir_char, queue->local_insert,
+		queue->remote_insert, queue->process);
+
+	return status;
+
+unlock_both_error_exit:
+	mutex_unlock(&state->slot_mutex);
+cancel_bulk_error_exit:
+	vchiq_complete_bulk(service->instance, bulk);
+unlock_error_exit:
+	mutex_unlock(&service->bulk_mutex);
+
+	return status;
+}
+
 /* Called by the slot handler */
 int
 vchiq_close_service_internal(struct vchiq_service *service, int close_recvd)
@@ -2991,15 +3101,9 @@ int vchiq_bulk_transfer(struct vchiq_instance *instance, unsigned int handle,
 			enum vchiq_bulk_mode mode, enum vchiq_bulk_dir dir)
 {
 	struct vchiq_service *service = find_service_by_handle(instance, handle);
-	struct vchiq_bulk_queue *queue;
-	struct vchiq_bulk *bulk;
-	struct vchiq_state *state;
 	struct bulk_waiter *bulk_waiter = NULL;
-	const char dir_char = (dir == VCHIQ_BULK_TRANSMIT) ? 't' : 'r';
-	const int dir_msgtype = (dir == VCHIQ_BULK_TRANSMIT) ?
-		VCHIQ_MSG_BULK_TX : VCHIQ_MSG_BULK_RX;
+	struct vchiq_bulk *bulk;
 	int status = -EINVAL;
-	int payload[2];
 
 	if (!service)
 		goto error_exit;
@@ -3027,89 +3131,10 @@ int vchiq_bulk_transfer(struct vchiq_instance *instance, unsigned int handle,
 		goto error_exit;
 	}
 
-	state = service->state;
-
-	queue = (dir == VCHIQ_BULK_TRANSMIT) ?
-		&service->bulk_tx : &service->bulk_rx;
-
-	if (mutex_lock_killable(&service->bulk_mutex)) {
-		status = -EAGAIN;
-		goto error_exit;
-	}
-
-	if (queue->local_insert == queue->remove + VCHIQ_NUM_SERVICE_BULKS) {
-		VCHIQ_SERVICE_STATS_INC(service, bulk_stalls);
-		do {
-			mutex_unlock(&service->bulk_mutex);
-			if (wait_for_completion_interruptible(&service->bulk_remove_event)) {
-				status = -EAGAIN;
-				goto error_exit;
-			}
-			if (mutex_lock_killable(&service->bulk_mutex)) {
-				status = -EAGAIN;
-				goto error_exit;
-			}
-		} while (queue->local_insert == queue->remove +
-				VCHIQ_NUM_SERVICE_BULKS);
-	}
-
-	bulk = &queue->bulks[BULK_INDEX(queue->local_insert)];
-
-	bulk->mode = mode;
-	bulk->dir = dir;
-	bulk->userdata = userdata;
-	bulk->size = size;
-	bulk->actual = VCHIQ_BULK_ACTUAL_ABORTED;
-
-	if (vchiq_prepare_bulk_data(instance, bulk, offset, uoffset, size, dir))
-		goto unlock_error_exit;
-
-	/*
-	 * Ensure that the bulk data record is visible to the peer
-	 * before proceeding.
-	 */
-	wmb();
-
-	dev_dbg(state->dev, "core: %d: bt (%d->%d) %cx %x@%pad %pK\n",
-		state->id, service->localport, service->remoteport,
-		dir_char, size, &bulk->data, userdata);
-
-	/*
-	 * The slot mutex must be held when the service is being closed, so
-	 * claim it here to ensure that isn't happening
-	 */
-	if (mutex_lock_killable(&state->slot_mutex)) {
-		status = -EAGAIN;
-		goto cancel_bulk_error_exit;
-	}
-
-	if (service->srvstate != VCHIQ_SRVSTATE_OPEN)
-		goto unlock_both_error_exit;
-
-	payload[0] = lower_32_bits(bulk->data);
-	payload[1] = bulk->size;
-	status = queue_message(state,
-			       NULL,
-			       VCHIQ_MAKE_MSG(dir_msgtype,
-					      service->localport,
-					      service->remoteport),
-			       memcpy_copy_callback,
-			       &payload,
-			       sizeof(payload),
-			       QMFLAGS_IS_BLOCKING |
-			       QMFLAGS_NO_MUTEX_LOCK |
-			       QMFLAGS_NO_MUTEX_UNLOCK);
+	status = vchiq_bulk_xfer_queue_msg_interruptible(service, offset, uoffset,
+							 size, userdata, mode, dir);
 	if (status)
-		goto unlock_both_error_exit;
-
-	queue->local_insert++;
-
-	mutex_unlock(&state->slot_mutex);
-	mutex_unlock(&service->bulk_mutex);
-
-	dev_dbg(state->dev, "core: %d: bt:%d %cx li=%x ri=%x p=%x\n",
-		state->id, service->localport, dir_char, queue->local_insert,
-		queue->remote_insert, queue->process);
+		goto error_exit;
 
 	vchiq_service_put(service);
 
@@ -3123,13 +3148,6 @@ int vchiq_bulk_transfer(struct vchiq_instance *instance, unsigned int handle,
 
 	return 0;
 
-unlock_both_error_exit:
-	mutex_unlock(&state->slot_mutex);
-cancel_bulk_error_exit:
-	vchiq_complete_bulk(service->instance, bulk);
-unlock_error_exit:
-	mutex_unlock(&service->bulk_mutex);
-
 error_exit:
 	if (service)
 		vchiq_service_put(service);