From f5316b4aea024da9266d740322a5481657f6ce59 Mon Sep 17 00:00:00 2001
From: Jason Wessel <jason.wessel@windriver.com>
Date: Thu, 20 May 2010 21:04:22 -0500
Subject: kgdb,8250,pl011: Return immediately from console poll

The design of the kdb shell requires that every device that can
provide input to kdb have a polling routine that exits immediately if
there is no character available.  This is required in order to get the
page scrolling mechanism working.

Changing the kernel debugger I/O API to require all polling character
routines to exit immediately if there is no data allows the kernel
debugger to process multiple input channels.

NO_POLL_CHAR will be the return code to the polling routine when ever
there is no character available.

CC: linux-serial@vger.kernel.org
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
---
 kernel/debug/gdbstub.c | 37 +++++++++++++++++++++++++++++++------
 1 file changed, 31 insertions(+), 6 deletions(-)

(limited to 'kernel/debug/gdbstub.c')

diff --git a/kernel/debug/gdbstub.c b/kernel/debug/gdbstub.c
index 188203a1965..3c000490a7d 100644
--- a/kernel/debug/gdbstub.c
+++ b/kernel/debug/gdbstub.c
@@ -30,6 +30,7 @@
 
 #include <linux/kernel.h>
 #include <linux/kgdb.h>
+#include <linux/kdb.h>
 #include <linux/reboot.h>
 #include <linux/uaccess.h>
 #include <asm/cacheflush.h>
@@ -62,6 +63,30 @@ static int hex(char ch)
 	return -1;
 }
 
+#ifdef CONFIG_KGDB_KDB
+static int gdbstub_read_wait(void)
+{
+	int ret = -1;
+	int i;
+
+	/* poll any additional I/O interfaces that are defined */
+	while (ret < 0)
+		for (i = 0; kdb_poll_funcs[i] != NULL; i++) {
+			ret = kdb_poll_funcs[i]();
+			if (ret > 0)
+				break;
+		}
+	return ret;
+}
+#else
+static int gdbstub_read_wait(void)
+{
+	int ret = dbg_io_ops->read_char();
+	while (ret == NO_POLL_CHAR)
+		ret = dbg_io_ops->read_char();
+	return ret;
+}
+#endif
 /* scan for the sequence $<data>#<checksum> */
 static void get_packet(char *buffer)
 {
@@ -75,7 +100,7 @@ static void get_packet(char *buffer)
 		 * Spin and wait around for the start character, ignore all
 		 * other characters:
 		 */
-		while ((ch = (dbg_io_ops->read_char())) != '$')
+		while ((ch = (gdbstub_read_wait())) != '$')
 			/* nothing */;
 
 		kgdb_connected = 1;
@@ -88,7 +113,7 @@ static void get_packet(char *buffer)
 		 * now, read until a # or end of buffer is found:
 		 */
 		while (count < (BUFMAX - 1)) {
-			ch = dbg_io_ops->read_char();
+			ch = gdbstub_read_wait();
 			if (ch == '#')
 				break;
 			checksum = checksum + ch;
@@ -98,8 +123,8 @@ static void get_packet(char *buffer)
 		buffer[count] = 0;
 
 		if (ch == '#') {
-			xmitcsum = hex(dbg_io_ops->read_char()) << 4;
-			xmitcsum += hex(dbg_io_ops->read_char());
+			xmitcsum = hex(gdbstub_read_wait()) << 4;
+			xmitcsum += hex(gdbstub_read_wait());
 
 			if (checksum != xmitcsum)
 				/* failed checksum */
@@ -144,10 +169,10 @@ static void put_packet(char *buffer)
 			dbg_io_ops->flush();
 
 		/* Now see what we get in reply. */
-		ch = dbg_io_ops->read_char();
+		ch = gdbstub_read_wait();
 
 		if (ch == 3)
-			ch = dbg_io_ops->read_char();
+			ch = gdbstub_read_wait();
 
 		/* If we get an ACK, we are done. */
 		if (ch == '+')
-- 
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