scsi: imm: mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Notice that, in this particular case, I placed all the "Phase N - ..."
comments on the same line as its corresponding switch case. The same
way in which similar comments appear in drivers/scsi/ppa.c. This makes
it possible to place the "fall through" annotations at the bottom of
each switch case, which is what GCC is expecting to find.
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

drivers/scsi/imm.c

@@ -796,21 +796,21 @@ static int imm_engine(imm_struct *dev, struct scsi_cmnd *cmd)
 			return 0;
 		}
 		return 1;	/* wait until imm_wakeup claims parport */
-		/* Phase 1 - Connected */
-	case 1:
+
+	case 1:		/* Phase 1 - Connected */
 		imm_connect(dev, CONNECT_EPP_MAYBE);
 		cmd->SCp.phase++;
+		/* fall through */
 
-		/* Phase 2 - We are now talking to the scsi bus */
-	case 2:
+	case 2:		/* Phase 2 - We are now talking to the scsi bus */
 		if (!imm_select(dev, scmd_id(cmd))) {
 			imm_fail(dev, DID_NO_CONNECT);
 			return 0;
 		}
 		cmd->SCp.phase++;
+		/* fall through */
 
-		/* Phase 3 - Ready to accept a command */
-	case 3:
+	case 3:		/* Phase 3 - Ready to accept a command */
 		w_ctr(ppb, 0x0c);
 		if (!(r_str(ppb) & 0x80))
 			return 1;
@@ -818,9 +818,9 @@ static int imm_engine(imm_struct *dev, struct scsi_cmnd *cmd)
 		if (!imm_send_command(cmd))
 			return 0;
 		cmd->SCp.phase++;
+		/* fall through */
 
-		/* Phase 4 - Setup scatter/gather buffers */
-	case 4:
+	case 4:		/* Phase 4 - Setup scatter/gather buffers */
 		if (scsi_bufflen(cmd)) {
 			cmd->SCp.buffer = scsi_sglist(cmd);
 			cmd->SCp.this_residual = cmd->SCp.buffer->length;
@@ -834,8 +834,9 @@ static int imm_engine(imm_struct *dev, struct scsi_cmnd *cmd)
 		cmd->SCp.phase++;
 		if (cmd->SCp.this_residual & 0x01)
 			cmd->SCp.this_residual++;
-		/* Phase 5 - Pre-Data transfer stage */
-	case 5:
+		/* fall through */
+
+	case 5:		/* Phase 5 - Pre-Data transfer stage */
 		/* Spin lock for BUSY */
 		w_ctr(ppb, 0x0c);
 		if (!(r_str(ppb) & 0x80))
@@ -850,9 +851,9 @@ static int imm_engine(imm_struct *dev, struct scsi_cmnd *cmd)
 			if (imm_negotiate(dev))
 				return 0;
 		cmd->SCp.phase++;
+		/* fall through */
 
-		/* Phase 6 - Data transfer stage */
-	case 6:
+	case 6:		/* Phase 6 - Data transfer stage */
 		/* Spin lock for BUSY */
 		w_ctr(ppb, 0x0c);
 		if (!(r_str(ppb) & 0x80))
@@ -866,9 +867,9 @@ static int imm_engine(imm_struct *dev, struct scsi_cmnd *cmd)
 				return 1;
 		}
 		cmd->SCp.phase++;
+		/* fall through */
 
-		/* Phase 7 - Post data transfer stage */
-	case 7:
+	case 7:		/* Phase 7 - Post data transfer stage */
 		if ((dev->dp) && (dev->rd)) {
 			if ((dev->mode == IMM_NIBBLE) || (dev->mode == IMM_PS2)) {
 				w_ctr(ppb, 0x4);
@@ -878,9 +879,9 @@ static int imm_engine(imm_struct *dev, struct scsi_cmnd *cmd)
 			}
 		}
 		cmd->SCp.phase++;
+		/* fall through */
 
-		/* Phase 8 - Read status/message */
-	case 8:
+	case 8:		/* Phase 8 - Read status/message */
 		/* Check for data overrun */
 		if (imm_wait(dev) != (unsigned char) 0xb8) {
 			imm_fail(dev, DID_ERROR);