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