New patch to review for coreboot: 366ff1e console: add qemu debugcon detection

[Gerd Hoffmann]

Gerd Hoffmann ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/3338

-gerrit

commit 366ff1e90049c7ae98d39f1d99ca67342cd1fa87
Author: Gerd Hoffmann 
Date:   Thu May 30 10:33:38 2013 +0200

console: add qemu debugcon detection

The qemu debugcon port returns 0xe9 on reads in case the device is
    present.  Use that for detection and write console output to the
    port only in case the device is actually present.

Change-Id: I41aabcf11845d24004e4f795dfd799822fd14646
    Signed-off-by: Gerd Hoffmann 
---
 src/console/qemu_debugcon_console.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/console/qemu_debugcon_console.c b/src/console/qemu_debugcon_console.c
index 3037e36..e2591ba 100644
--- a/src/console/qemu_debugcon_console.c
+++ b/src/console/qemu_debugcon_console.c
@@ -21,13 +21,18 @@
 #include <console/console.h>
 #include <arch/io.h>

+static unsigned char readback;
+
 static void debugcon_init(void)
 {
+	readback = inb(CONFIG_CONSOLE_QEMU_DEBUGCON_PORT);
 }

static void debugcon_tx_byte(unsigned char data)
 {
-	outb(data, CONFIG_CONSOLE_QEMU_DEBUGCON_PORT);
+	if (readback == 0xe9) {
+		outb(data, CONFIG_CONSOLE_QEMU_DEBUGCON_PORT);
+	}
 }

static void debugcon_tx_flush(void)