[PATCH] Staging: speakup: Fix getting port information

[Samuel Thibault]

5e6dc54 broke the port information in the speakup driver:
SERIAL_PORT_DFNS only gets defined if asm/serial.h is included.

Along the way, make sure that we do have information for the requested
serial port number (index)

Signed-off-by: Samuel Thibault <samuel.thibault at ens-lyon.org>

--- a/drivers/staging/speakup/serialio.c
+++ b/drivers/staging/speakup/serialio.c
@@ -6,6 +6,9 @@
 #include "spk_priv.h"
 #include "serialio.h"
 
+#include <linux/serial_core.h>
+#include <asm/serial.h>
+
 #ifndef SERIAL_PORT_DFNS
 #define SERIAL_PORT_DFNS
 #endif
@@ -26,6 +29,11 @@ const struct old_serial_port *spk_serial
 	const struct old_serial_port *ser = rs_table + index;
 	int err;
 
+	if (index > sizeof(rs_table) / sizeof(*rs_table)) {
+		pr_info("no port info for ttyS%d\n", index);
+		return NULL;
+	}
+
 	/*	Divisor, bytesize and parity */
 	quot = ser->baud_base / baud;
 	cval = cflag & (CSIZE | CSTOPB);