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

@@ -334,6 +334,23 @@ 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;
+
 /**
  * @brief Resource table remote processor vendor specific entry
  *

lib/include/openamp/rpmsg_virtio.h

@@ -29,6 +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 */
 
 #ifdef VIRTIO_CACHED_BUFFERS
 #warning "VIRTIO_CACHED_BUFFERS is deprecated, please use VIRTIO_USE_DCACHE"

lib/rpmsg/rpmsg_virtio.c

@@ -12,6 +12,7 @@
 #include <metal/sleep.h>
 #include <metal/utilities.h>
 #include <openamp/rpmsg_virtio.h>
+#include <openamp/remoteproc.h>
 #include <openamp/virtqueue.h>
 
 #include "rpmsg_internal.h"
@@ -808,6 +809,7 @@ int rpmsg_init_vdev_with_config(struct rpmsg_virtio_device *rvdev,
 	struct rpmsg_device *rdev;
 	const char *vq_names[RPMSG_NUM_VRINGS];
 	vq_callback callback[RPMSG_NUM_VRINGS];
+	struct fw_rsc_config fw_config;
 	int status;
 	unsigned int i, role;
 
@@ -854,6 +856,13 @@ 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, &fw_config, sizeof(fw_config));
+		rvdev->config.h2r_buf_size = fw_config.h2r_buf_size;
+		rvdev->config.r2h_buf_size = fw_config.r2h_buf_size;
+	}
+
 #ifndef VIRTIO_DEVICE_ONLY
 	if (role == RPMSG_HOST) {
 		/*