[console] Add support for the bochs/qemu debug port console

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/x86/core/debugcon.c

+/*
+ * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/** @file
+ *
+ * Debug port console
+ *
+ * The debug port is supported by bochs (via the "port_e9_hack"
+ * configuration file directive) and by qemu (via the "-debugcon"
+ * command-line option).
+ */
+
+#include <stdint.h>
+#include <ipxe/io.h>
+#include <ipxe/console.h>
+#include <ipxe/init.h>
+#include <config/console.h>
+
+/** Debug port */
+#define DEBUG_PORT 0xe9
+
+/** Debug port installation check magic value */
+#define DEBUG_PORT_CHECK 0xe9
+
+/* Set default console usage if applicable */
+#if ! ( defined ( CONSOLE_DEBUGCON ) && CONSOLE_EXPLICIT ( CONSOLE_DEBUGCON ) )
+#undef CONSOLE_DEBUGCON
+#define CONSOLE_DEBUGCON ( CONSOLE_USAGE_ALL & ~CONSOLE_USAGE_TUI )
+#endif
+
+/**
+ * Print a character to debug port console
+ *
+ * @v character		Character to be printed
+ */
+static void debugcon_putchar ( int character ) {
+
+	/* Write character to debug port */
+	outb ( character, DEBUG_PORT );
+}
+
+/** Debug port console driver */
+struct console_driver debugcon_console __console_driver = {
+	.putchar = debugcon_putchar,
+	.usage = CONSOLE_DEBUGCON,
+};
+
+/**
+ * Initialise debug port console
+ *
+ */
+static void debugcon_init ( void ) {
+	uint8_t check;
+
+	/* Check if console is present */
+	check = inb ( DEBUG_PORT );
+	if ( check != DEBUG_PORT_CHECK ) {
+		DBG ( "Debug port not present; disabling console\n" );
+		debugcon_console.disabled = 1;
+	}
+}
+
+/**
+ * Debug port console initialisation function
+ */
+struct init_fn debugcon_init_fn __init_fn ( INIT_EARLY ) = {
+	.initialise = debugcon_init,
+};

src/config/config.c

 #ifdef CONSOLE_VMWARE
 REQUIRE_OBJECT ( vmconsole );
 #endif
+#ifdef CONSOLE_DEBUGCON
+REQUIRE_OBJECT ( debugcon );
+#endif
 
 /*
  * Drag in all requested network protocols

src/config/console.h

 //#define	CONSOLE_SYSLOG		/* Syslog console */
 //#define	CONSOLE_SYSLOGS		/* Encrypted syslog console */
 //#define	CONSOLE_VMWARE		/* VMware logfile console */
+//#define	CONSOLE_DEBUGCON	/* Debug port console */
 
 #define	KEYBOARD_MAP	us