dma-buf: Support negotiation between exporter and importer

Allow the exporter and importer to recognize each other and to set up a
shared region of memory for the purpose of mapping requirement
negotiation.

Tracked-On: OAM-129610
Signed-off-by: Weifeng Liu <weifeng.liu@intel.com>

drivers/dma-buf/dma-buf.c

@@ -978,8 +978,9 @@ EXPORT_SYMBOL_NS_GPL(dma_buf_dynamic_attach, DMA_BUF);
  */
 struct dma_buf_attachment *
 ____dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
-			const struct dma_buf_attach_ops *importer_ops,
-			void *importer_priv, bool p2p)
+			   unsigned importer_type_id, void *shared,
+			   const struct dma_buf_attach_ops *importer_ops,
+			   void *importer_priv, bool p2p)
 {
 	struct dma_buf_attachment *attach;
 	int ret;
@@ -995,6 +996,8 @@ ____dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
 		return ERR_PTR(-ENOMEM);
 
 	attach->dev = dev;
+	attach->importer_type_id = importer_type_id;
+	attach->shared = shared;
 	attach->dmabuf = dmabuf;
 	if (importer_ops)
 		attach->peer2peer = importer_ops->allow_peer2peer;

include/linux/dma-buf.h

@@ -533,8 +533,34 @@ struct dma_buf {
 
 	ANDROID_KABI_RESERVE(1);
 	ANDROID_KABI_RESERVE(2);
+
+	/**
+	 * @exporter_id:
+	 *
+	 * Globally unique id for importer identifying exporter type (driver).
+	 * Based on this info, the importer could leverage shared field in
+	 * dmabuf attachment for negotiation.
+	 */
+	unsigned exporter_type_id;
 };
 
+#define DMA_BUF_DRIVER_TYPE_ID_GENERAL				0
+#define DMA_BUF_DRIVER_TYPE_ID_I915_BACKPORTS			1
+#define DMA_BUF_DRIVER_TYPE_ID_VIRTIO_GPU			2
+
+#define VIRTIO_GPU_DMABUF_ATTACH_SHARED_CURRENT_VERSION		1
+#define VIRTIO_GPU_DMABUF_ATTACH_SHARED_FLAG_LMEM		(1lu << 0)
+
+struct virtio_gpu_dmabuf_attach_shared {
+	uint32_t version;
+	union {
+		struct {
+			uint32_t flags;
+		} v1;
+	} shared;
+};
+
+
 /**
  * struct dma_buf_attach_ops - importer operations for an attachment
  *
@@ -585,6 +611,10 @@ struct dma_buf_attach_ops {
  * @importer_priv: importer specific attachment data.
  * @dma_map_attrs: DMA attributes to be used when the exporter maps the buffer
  * through dma_buf_map_attachment.
+ * @importer_type_id: used by exporter for identifying the importer
+ * @shared: shared by both exporter and importer for negotiation on the
+ * DMA mapping requirements. Should be used only when importer recognizes the
+ * exporter and be allocated/cleaned up by the importer.
  *
  * This structure holds the attachment information between the dma_buf buffer
  * and its user device(s). The list contains one attachment struct per device
@@ -609,6 +639,8 @@ struct dma_buf_attachment {
 
 	ANDROID_KABI_RESERVE(1);
 	ANDROID_KABI_RESERVE(2);
+	unsigned importer_type_id;
+	void *shared;
 };
 
 /**
@@ -700,6 +732,7 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
 		       void *importer_priv);
 struct dma_buf_attachment *
 ____dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
+			   unsigned importer_type_id, void *shared,
 		           const struct dma_buf_attach_ops *importer_ops,
 		           void *importer_priv, bool p2p);
 void dma_buf_detach(struct dma_buf *dmabuf,