virtio: Add memory operation interface for virtio device

Buffer management is different for different transport layer:

For MMIO transport layer, the buffer can directly allocated from
the geust OS heap beacase the hypervisor can access all the memory own
by guest OS.

For remoteproc transport layer, the buffer should be allocated from
the share memory region to make sure the remote core can access this
buffer too.

So add memory ops in virtio device to make different transport/device can
implement their own share memory management.

Signed-off-by: Bowen Wang <wangbowen6@xiaomi.com>

lib/include/openamp/virtio.h

@@ -152,6 +152,7 @@ struct virtio_device_id {
 typedef void (*virtio_dev_reset_cb)(struct virtio_device *vdev);
 
 struct virtio_dispatch;
+struct virtio_memory_ops;
 
 /** @brief Device features. */
 struct virtio_feature_desc {
@@ -197,6 +198,9 @@ struct virtio_device {
 	/** Virtio dispatch table */
 	const struct virtio_dispatch *func;
 
+	/**< Virtio device memory operations */
+	const struct virtio_memory_ops *mmops;
+
 	/** Private data */
 	void *priv;
 
@@ -282,6 +286,14 @@ struct virtio_dispatch {
 	void (*notify)(struct virtqueue *vq);
 };
 
+struct virtio_memory_ops {
+	/** Allocate memory from the virtio device. */
+	void *(*alloc)(struct virtio_device *dev, size_t size, size_t align);
+
+	/** Free memory allocated from the virtio device. */
+	void (*free)(struct virtio_device *dev, void *buf);
+};
+
 /**
  * @brief Create the virtio device virtqueue.
  *
@@ -499,6 +511,54 @@ static inline int virtio_reset_device(struct virtio_device *vdev)
 	return 0;
 }
 
+/**
+ * @brief Allocate buffer from the virtio device
+ *
+ * @param vdev	Pointer to virtio device structure.
+ * @param buf	Pointer to the allocated buffer (virtual address).
+ * @param size	Allocated buffer size.
+ * @param align	Allocated buffer alignment.
+ *
+ * @return 0 on success, otherwise error code.
+ */
+static inline int virtio_alloc_buf(struct virtio_device *vdev, void **buf,
+				   size_t size, size_t align)
+{
+	if (!vdev || !buf)
+		return -EINVAL;
+
+	if (!vdev->mmops || !vdev->mmops->alloc)
+		return -ENXIO;
+
+	*buf = vdev->mmops->alloc(vdev, size, align);
+	if (!*buf)
+		return -ENOMEM;
+
+	return 0;
+}
+
+/**
+ * @brief Free the buffer allocated by \ref virtio_alloc_buf from the virtio
+ * device.
+ *
+ * @param vdev	Pointer to virtio device structure.
+ * @param buf	Buffer need to be freed.
+ *
+ * @return 0 on success, otherwise error code.
+ */
+static inline int virtio_free_buf(struct virtio_device *vdev, void *buf)
+{
+	if (!vdev)
+		return -EINVAL;
+
+	if (!vdev->mmops || !vdev->mmops->free)
+		return -ENXIO;
+
+	vdev->mmops->free(vdev, buf);
+
+	return 0;
+}
+
 #if defined __cplusplus
 }
 #endif