Staging: dgrp: Refactor the function dgrp_receive() in drrp_net_ops.c

The function dgrp_receive() in dgrp_net_ops.c is too long and can be
refactored. It uses various switch statements and goto labels. I have
removed a label called data and tried to extract a new function out of
it called as handle_data_in_packet().

This helps to make the code more modularize and simple to read and
understand.
Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dgrp/dgrp_net_ops.c

@@ -2232,114 +2232,20 @@ static ssize_t dgrp_net_read(struct file *file, char __user *buf, size_t count,
 	return rtn;
 }
 
-/**
- * dgrp_receive() -- decode data packets received from the remote PortServer.
- * @nd: pointer to a node structure
+/*
+ * Common Packet Handling code
  */
-static void dgrp_receive(struct nd_struct *nd)
+
+static void handle_data_in_packet(struct nd_struct *nd, struct ch_struct *ch,
+				  long dlen, long plen, int n1, u8 *dbuf)
 {
-	struct ch_struct *ch;
-	u8 *buf;
-	u8 *b;
-	u8 *dbuf;
 	char *error;
-	long port;
-	long dlen;
-	long plen;
-	long remain;
 	long n;
-	long mlast;
-	long elast;
-	long mstat;
-	long estat;
-
-	char ID[3];
-
-	nd->nd_tx_time = jiffies;
-
-	ID_TO_CHAR(nd->nd_ID, ID);
+	long remain;
+	u8 *buf;
+	u8 *b;
 
-	b = buf = nd->nd_iobuf;
 	remain = nd->nd_remain;
-
-	/*
-	 *  Loop to process Realport protocol packets.
-	 */
-
-	while (remain > 0) {
-		int n0 = b[0] >> 4;
-		int n1 = b[0] & 0x0f;
-
-		if (n0 <= 12) {
-			port = (nd->nd_rx_module << 4) + n1;
-
-			if (port >= nd->nd_chan_count) {
-				error = "Improper Port Number";
-				goto prot_error;
-			}
-
-			ch = nd->nd_chan + port;
-		} else {
-			port = -1;
-			ch = NULL;
-		}
-
-		/*
-		 *  Process by major packet type.
-		 */
-
-		switch (n0) {
-
-		/*
-		 *  Process 1-byte header data packet.
-		 */
-
-		case 0:
-		case 1:
-		case 2:
-		case 3:
-		case 4:
-		case 5:
-		case 6:
-		case 7:
-			dlen = n0 + 1;
-			plen = dlen + 1;
-
-			dbuf = b + 1;
-			goto data;
-
-		/*
-		 *  Process 2-byte header data packet.
-		 */
-
-		case 8:
-			if (remain < 3)
-				goto done;
-
-			dlen = b[1];
-			plen = dlen + 2;
-
-			dbuf = b + 2;
-			goto data;
-
-		/*
-		 *  Process 3-byte header data packet.
-		 */
-
-		case 9:
-			if (remain < 4)
-				goto done;
-
-			dlen = get_unaligned_be16(b + 1);
-			plen = dlen + 3;
-
-			dbuf = b + 3;
-
-		/*
-		 *  Common packet handling code.
-		 */
-
-data:
 	nd->nd_tx_work = 1;
 
 	/*
@@ -2349,7 +2255,9 @@ static void dgrp_receive(struct nd_struct *nd)
 
 	if (ch->ch_state < CS_READY) {
 		error = "Data received before RWIN established";
-				goto prot_error;
+		nd->nd_remain = 0;
+		nd->nd_state = NS_SEND_ERROR;
+		nd->nd_error = error;
 	}
 
 	/*
@@ -2361,7 +2269,9 @@ static void dgrp_receive(struct nd_struct *nd)
 
 	if (dlen > n) {
 		error = "Receive data overrun";
-				goto prot_error;
+		nd->nd_remain = 0;
+		nd->nd_state = NS_SEND_ERROR;
+		nd->nd_error = error;
 	}
 
 	/*
@@ -2468,7 +2378,6 @@ static void dgrp_receive(struct nd_struct *nd)
 
 		if ((ch->ch_flag & CH_INPUT) != 0) {
 			ch->ch_flag &= ~CH_INPUT;
-
 			wake_up_interruptible(&ch->ch_flag_wait);
 		}
 	}
@@ -2486,8 +2395,119 @@ static void dgrp_receive(struct nd_struct *nd)
 		put_unaligned_be16(dlen, b + 1);
 
 		remain = 3;
-				goto done;
+		if (remain > 0 && b != buf)
+			memcpy(buf, b, remain);
+
+		nd->nd_remain = remain;
+		return;
+	}
+}
+
+/**
+ * dgrp_receive() -- decode data packets received from the remote PortServer.
+ * @nd: pointer to a node structure
+ */
+static void dgrp_receive(struct nd_struct *nd)
+{
+	struct ch_struct *ch;
+	u8 *buf;
+	u8 *b;
+	u8 *dbuf;
+	char *error;
+	long port;
+	long dlen;
+	long plen;
+	long remain;
+	long n;
+	long mlast;
+	long elast;
+	long mstat;
+	long estat;
+
+	char ID[3];
+
+	nd->nd_tx_time = jiffies;
+
+	ID_TO_CHAR(nd->nd_ID, ID);
+
+	b = buf = nd->nd_iobuf;
+	remain = nd->nd_remain;
+
+	/*
+	 *  Loop to process Realport protocol packets.
+	 */
+
+	while (remain > 0) {
+		int n0 = b[0] >> 4;
+		int n1 = b[0] & 0x0f;
+
+		if (n0 <= 12) {
+			port = (nd->nd_rx_module << 4) + n1;
+
+			if (port >= nd->nd_chan_count) {
+				error = "Improper Port Number";
+				goto prot_error;
 			}
+
+			ch = nd->nd_chan + port;
+		} else {
+			port = -1;
+			ch = NULL;
+		}
+
+		/*
+		 *  Process by major packet type.
+		 */
+
+		switch (n0) {
+
+		/*
+		 *  Process 1-byte header data packet.
+		 */
+
+		case 0:
+		case 1:
+		case 2:
+		case 3:
+		case 4:
+		case 5:
+		case 6:
+		case 7:
+			dlen = n0 + 1;
+			plen = dlen + 1;
+
+			dbuf = b + 1;
+			handle_data_in_packet(nd, ch, dlen, plen, n1, dbuf);
+			break;
+
+		/*
+		 *  Process 2-byte header data packet.
+		 */
+
+		case 8:
+			if (remain < 3)
+				goto done;
+
+			dlen = b[1];
+			plen = dlen + 2;
+
+			dbuf = b + 2;
+			handle_data_in_packet(nd, ch, dlen, plen, n1, dbuf);
+			break;
+
+		/*
+		 *  Process 3-byte header data packet.
+		 */
+
+		case 9:
+			if (remain < 4)
+				goto done;
+
+			dlen = get_unaligned_be16(b + 1);
+			plen = dlen + 3;
+
+			dbuf = b + 3;
+
 			break;
 
 		/*