Negotiate individual buffer size dynamically

If slave support VIRTIO_RPMSG_F_BUFSZ(0x04) feature, master
determine the buffer size from config space(first 8 bytes),
otherwise the default size(512 bytes) will be used.

Signed-off-by: Chao An <anchao@pinecone.net>

Author: anchao

lib/include/openamp/remoteproc.h

@@ -303,6 +303,23 @@ struct fw_rsc_vdev {
 	struct fw_rsc_vdev_vring vring[0];
 } METAL_PACKED_END;
 
+/**
+ * struct fw_rsc_config - configuration space declaration
+ * @h2r_buf_size: the size of the buffer used to send data from host to remote
+ * @r2h_buf_size: the size of the buffer used to send data from remote to host
+ * @reserved: reserved (must be zero)
+ *
+ * This structure immediately follow fw_rsc_vdev to provide the config info.
+ */
+METAL_PACKED_BEGIN
+struct fw_rsc_config {
+	/* The individual buffer size(if VIRTIO_RPMSG_F_BUFSZ) */
+	uint32_t h2r_buf_size;
+	uint32_t r2h_buf_size;
+	uint32_t reserved[14]; /* Reserve for the future use */
+	/* Put the customize config here */
+} METAL_PACKED_END;
+
 /**
  * struct fw_rsc_vendor - remote processor vendor specific resource
  * @len: length of the resource

lib/include/openamp/rpmsg_virtio.h

@@ -16,6 +16,7 @@
 #include <metal/mutex.h>
 #include <openamp/rpmsg.h>
 #include <openamp/virtio.h>
+#include <openamp/remoteproc.h>
 
 #if defined __cplusplus
 extern "C" {
@@ -28,6 +29,7 @@ extern "C" {
 
 /* The feature bitmap for virtio rpmsg */
 #define VIRTIO_RPMSG_F_NS	0 /* RP supports name service notifications */
+#define VIRTIO_RPMSG_F_BUFSZ	2 /* RP supports buffer size negotiation */
 
 /**
  * struct rpmsg_virtio_shm_pool - shared memory pool used for rpmsg buffers
@@ -74,7 +76,7 @@ struct rpmsg_virtio_config {
  */
 struct rpmsg_virtio_device {
 	struct rpmsg_device rdev;
-	struct rpmsg_virtio_config config;
+	struct fw_rsc_config config;
 	struct virtio_device *vdev;
 	struct virtqueue *rvq;
 	struct virtqueue *svq;

lib/rpmsg/rpmsg_virtio.c

@@ -651,7 +651,8 @@ int rpmsg_init_vdev_with_config(struct rpmsg_virtio_device *rvdev,
 		if (config == NULL) {
 			return RPMSG_ERR_PARAM;
 		}
-		rvdev->config = *config;
+		rvdev->config.h2r_buf_size = config->h2r_buf_size;
+		rvdev->config.r2h_buf_size = config->r2h_buf_size;
 	}
 #else /*!VIRTIO_SLAVE_ONLY*/
 	/* Ignore passed config in the virtio-device-only configuration. */
@@ -668,6 +669,13 @@ int rpmsg_init_vdev_with_config(struct rpmsg_virtio_device *rvdev,
 	vdev->features = rpmsg_virtio_get_features(rvdev);
 	rdev->support_ns = !!(vdev->features & (1 << VIRTIO_RPMSG_F_NS));
 
+	if (vdev->features & (1 << VIRTIO_RPMSG_F_BUFSZ)) {
+		rpmsg_virtio_read_config(rvdev,
+			0,
+			&rvdev->config,
+			sizeof(rvdev->config));
+	}
+
 #ifndef VIRTIO_SLAVE_ONLY
 	if (role == RPMSG_MASTER) {
 		/*