To make it clear what's required and what's not. Also, some of the
values don't seem like a good defaults; for example eth1.

Move the invocation comment to the top, add missing -s to the client
and cleanup the client invocation a bit to make more readable.

Reviewed-by: Mina Almasry <almasrymina@google.com>
Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
---
 tools/testing/selftests/net/ncdevmem.c | 61 ++++++++++++++++----------
 1 file changed, 39 insertions(+), 22 deletions(-)

diff --git a/tools/testing/selftests/net/ncdevmem.c b/tools/testing/selftests/net/ncdevmem.c
index b94f7c4a53ed..037fb6e97d29 100644
--- a/tools/testing/selftests/net/ncdevmem.c
+++ b/tools/testing/selftests/net/ncdevmem.c
@@ -1,4 +1,31 @@
 // SPDX-License-Identifier: GPL-2.0
+/*
+ * tcpdevmem netcat. Works similarly to netcat but does device memory TCP
+ * instead of regular TCP. Uses udmabuf to mock a dmabuf provider.
+ *
+ * Usage:
+ *
+ *     On server:
+ *     ncdevmem -s <server IP> [-c <client IP>] -f eth1 -l -p 5201
+ *
+ *     On client:
+ *     echo -n "hello\nworld" | nc -s <server IP> 5201 -p 5201
+ *
+ * Test data validation:
+ *
+ *     On server:
+ *     ncdevmem -s <server IP> [-c <client IP>] -f eth1 -l -p 5201 -v 7
+ *
+ *     On client:
+ *     yes $(echo -e \\x01\\x02\\x03\\x04\\x05\\x06) | \
+ *             tr \\n \\0 | \
+ *             head -c 5G | \
+ *             nc <server IP> 5201 -p 5201
+ *
+ *
+ * Note this is compatible with regular netcat. i.e. the sender or receiver can
+ * be replaced with regular netcat to test the RX or TX path in isolation.
+ */
 #define _GNU_SOURCE
 #define __EXPORTED_HEADERS__
 
@@ -42,32 +69,13 @@
 #define MSG_SOCK_DEVMEM 0x2000000
 #endif
 
-/*
- * tcpdevmem netcat. Works similarly to netcat but does device memory TCP
- * instead of regular TCP. Uses udmabuf to mock a dmabuf provider.
- *
- * Usage:
- *
- *	On server:
- *	ncdevmem -s <server IP> -c <client IP> -f eth1 -l -p 5201 -v 7
- *
- *	On client:
- *	yes $(echo -e \\x01\\x02\\x03\\x04\\x05\\x06) | \
- *		tr \\n \\0 | \
- *		head -c 5G | \
- *		nc <server IP> 5201 -p 5201
- *
- * Note this is compatible with regular netcat. i.e. the sender or receiver can
- * be replaced with regular netcat to test the RX or TX path in isolation.
- */
-
-static char *server_ip = "192.168.1.4";
+static char *server_ip;
 static char *client_ip;
-static char *port = "5201";
+static char *port;
 static size_t do_validation;
 static int start_queue = 8;
 static int num_queues = 8;
-static char *ifname = "eth1";
+static char *ifname;
 static unsigned int ifindex;
 static unsigned int dmabuf_id;
 
@@ -596,6 +604,15 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	if (!server_ip)
+		error(1, 0, "Missing -s argument\n");
+
+	if (!port)
+		error(1, 0, "Missing -p argument\n");
+
+	if (!ifname)
+		error(1, 0, "Missing -f argument\n");
+
 	ifindex = if_nametoindex(ifname);
 
 	for (; optind < argc; optind++)
-- 
2.47.0