dsp: base: Added encode_pldm_base_negotiate_transfer_params_resp()

This command is based on DSP0240 v1.2.0 section 9.6.2
NegotiateTransferParameters (0x07).

gitlint-ignore: T1
Signed-off-by: Kasun Athukorala <kasunath@google.com>
Change-Id: I619ca0b356df065b662b16d4a469730fd145f9de
diff --git a/CHANGELOG.md b/CHANGELOG.md
index eb7e9a8..a996aa5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -23,6 +23,7 @@
   - Added `encode_pldm_platform_file_descriptor_pdr()`
 - utils: Added `pldm_edac_crc32_extend()`
 - base: Added `decode_pldm_base_negotiate_transfer_params_req()`
+- base: Added `encode_pldm_base_negotiate_transfer_params_resp()`
 
 ### Changed
 
diff --git a/include/libpldm/base.h b/include/libpldm/base.h
index b76b9f3..4be8d20 100644
--- a/include/libpldm/base.h
+++ b/include/libpldm/base.h
@@ -815,6 +815,23 @@
 	const struct pldm_base_negotiate_transfer_params_req *req,
 	struct pldm_msg *msg, size_t *payload_length);
 
+/** @brief Encode a PLDM Negotiate Transfer Parameters response message
+ *
+ *  @param[in] instance_id - Message's instance id
+ *  @param[in] resp - The pointer to the response message to be encoded
+ *  @param[out] msg - Message will be written to this
+ *  @param[in,out] payload_length - length of response message payload
+ *  @return 0 on success
+ *          -EINVAL if the input parameters' memory are not allocated,
+ *          or message type or instance in request header is invalid
+ *          -ENOMSG if the PLDM type in the request header is invalid
+ *          -EOVERFLOW if the input message length is invalid
+ */
+int encode_pldm_base_negotiate_transfer_params_resp(
+	uint8_t instance_id,
+	const struct pldm_base_negotiate_transfer_params_resp *resp,
+	struct pldm_msg *msg, size_t *payload_length);
+
 /** @brief Decode a PLDM Negotiate Transfer Parameters request message
  *
  *  @param[in] msg - Request message
diff --git a/src/dsp/base.c b/src/dsp/base.c
index 88dc883..a094cb2 100644
--- a/src/dsp/base.c
+++ b/src/dsp/base.c
@@ -832,6 +832,56 @@
 	return pldm_msgbuf_complete_used(buf, *payload_length, payload_length);
 }
 
+#define PLDM_BASE_MIN_PART_SIZE 256
+
+LIBPLDM_ABI_TESTING
+int encode_pldm_base_negotiate_transfer_params_resp(
+	uint8_t instance_id,
+	const struct pldm_base_negotiate_transfer_params_resp *resp,
+	struct pldm_msg *msg, size_t *payload_length)
+{
+	PLDM_MSGBUF_RW_DEFINE_P(buf);
+	int rc;
+
+	if (resp == NULL || msg == NULL) {
+		return -EINVAL;
+	}
+
+	if (resp->responder_part_size < PLDM_BASE_MIN_PART_SIZE) {
+		return -EINVAL;
+	}
+
+	struct pldm_header_info header = { 0 };
+	header.instance = instance_id;
+	header.msg_type = PLDM_RESPONSE;
+	header.pldm_type = PLDM_BASE;
+	header.command = PLDM_NEGOTIATE_TRANSFER_PARAMETERS;
+
+	rc = pack_pldm_header_errno(&header, &msg->hdr);
+	if (rc) {
+		return rc;
+	}
+
+	rc = pldm_msgbuf_init_errno(
+		buf, PLDM_BASE_NEGOTIATE_TRANSFER_PARAMETERS_RESP_BYTES,
+		msg->payload, *payload_length);
+	if (rc) {
+		return rc;
+	}
+
+	pldm_msgbuf_insert(buf, resp->completion_code);
+	pldm_msgbuf_insert(buf, resp->responder_part_size);
+	rc = pldm_msgbuf_insert_array(
+		buf, sizeof(resp->responder_protocol_support),
+		(uint8_t *)resp->responder_protocol_support,
+		sizeof(resp->responder_protocol_support));
+	if (rc) {
+		return pldm_msgbuf_discard(buf, rc);
+	}
+
+	return pldm_msgbuf_complete_used(buf, *payload_length, payload_length);
+}
+
 LIBPLDM_ABI_TESTING
 int decode_pldm_base_negotiate_transfer_params_req(
 	const struct pldm_msg *msg, size_t payload_length,
diff --git a/tests/dsp/base.cpp b/tests/dsp/base.cpp
index 80edb62..f146e7c 100644
--- a/tests/dsp/base.cpp
+++ b/tests/dsp/base.cpp
@@ -1833,3 +1833,91 @@
     EXPECT_EQ(rc, -EBADMSG);
 }
 #endif
+
+#ifdef LIBPLDM_API_TESTING
+TEST(NegotiateTransferParams, TestEncodeNegotiateTransferParamsRespPass)
+{
+    // Prepare encode parameters for a successful response
+    uint8_t instance_id = 0x0B;
+    uint8_t completion_code_success = PLDM_SUCCESS;
+    uint16_t responder_part_size = 2048; // 0x0800
+    bitfield8_t responder_protocol_support[8];
+    for (int i = 0; i < 8; ++i)
+    {
+        responder_protocol_support[i].byte = static_cast<uint8_t>(0xA0 + i);
+    }
+
+    struct pldm_base_negotiate_transfer_params_resp resp_params_success;
+    resp_params_success.completion_code = completion_code_success;
+    resp_params_success.responder_part_size = responder_part_size;
+    memcpy(resp_params_success.responder_protocol_support,
+           responder_protocol_support, sizeof(responder_protocol_support));
+
+    PLDM_MSG_DEFINE_P(response,
+                      PLDM_BASE_NEGOTIATE_TRANSFER_PARAMETERS_RESP_BYTES);
+    size_t payload_len = PLDM_BASE_NEGOTIATE_TRANSFER_PARAMETERS_RESP_BYTES;
+
+    // Encode success case
+    int rc = encode_pldm_base_negotiate_transfer_params_resp(
+        instance_id, &resp_params_success, response, &payload_len);
+    ASSERT_EQ(rc, 0);
+    EXPECT_EQ(response->hdr.request, PLDM_RESPONSE);
+    EXPECT_EQ(response->hdr.instance_id, instance_id);
+    EXPECT_EQ(response->hdr.type, PLDM_BASE);
+    EXPECT_EQ(response->hdr.command, PLDM_NEGOTIATE_TRANSFER_PARAMETERS);
+
+    // Verify the encoded response using the decode function
+    struct pldm_base_negotiate_transfer_params_resp decoded_resp;
+    payload_len = PLDM_BASE_NEGOTIATE_TRANSFER_PARAMETERS_RESP_BYTES;
+    rc = decode_pldm_base_negotiate_transfer_params_resp(response, payload_len,
+                                                         &decoded_resp);
+    ASSERT_EQ(rc, 0);
+    EXPECT_EQ(decoded_resp.completion_code, completion_code_success);
+    EXPECT_EQ(decoded_resp.responder_part_size, responder_part_size);
+    for (int i = 0; i < 8; ++i)
+    {
+        EXPECT_EQ(decoded_resp.responder_protocol_support[i].byte,
+                  responder_protocol_support[i].byte);
+    }
+}
+
+TEST(NegotiateTransferParams, TestEncodeNegotiateTransferParamsRespFail)
+{
+    // Prepare encode parameters
+    uint8_t instance_id = 0x0B;
+    uint8_t completion_code_success = PLDM_SUCCESS;
+    uint16_t responder_part_size = 2048; // 0x0800
+    bitfield8_t responder_protocol_support[8];
+    for (int i = 0; i < 8; ++i)
+    {
+        responder_protocol_support[i].byte = static_cast<uint8_t>(0xA0 + i);
+    }
+
+    struct pldm_base_negotiate_transfer_params_resp resp_params_success;
+    resp_params_success.completion_code = completion_code_success;
+    resp_params_success.responder_part_size = responder_part_size;
+    memcpy(resp_params_success.responder_protocol_support,
+           responder_protocol_support, sizeof(responder_protocol_support));
+
+    PLDM_MSG_DEFINE_P(response,
+                      PLDM_BASE_NEGOTIATE_TRANSFER_PARAMETERS_RESP_BYTES);
+    size_t payload_len = PLDM_BASE_NEGOTIATE_TRANSFER_PARAMETERS_RESP_BYTES;
+    int rc = 0;
+
+    // Null arguments
+    rc = encode_pldm_base_negotiate_transfer_params_resp(
+        instance_id, nullptr, response, &payload_len);
+    EXPECT_EQ(rc, -EINVAL);
+
+    payload_len = PLDM_BASE_NEGOTIATE_TRANSFER_PARAMETERS_RESP_BYTES;
+    rc = encode_pldm_base_negotiate_transfer_params_resp(
+        instance_id, &resp_params_success, nullptr, &payload_len);
+    EXPECT_EQ(rc, -EINVAL);
+
+    // Incorrect payload length
+    payload_len = PLDM_BASE_NEGOTIATE_TRANSFER_PARAMETERS_RESP_BYTES - 1;
+    rc = encode_pldm_base_negotiate_transfer_params_resp(
+        instance_id, &resp_params_success, response, &payload_len);
+    EXPECT_EQ(rc, -EOVERFLOW);
+}
+#endif