x86_uart.c

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/*
 * Copyright (C) 2014 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 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.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

/** @file
 *
 * 16550-compatible UART
 *
 */

#include <errno.h>
#include <ipxe/uart.h>

/** UART port bases */
static uint16_t uart_base[] = {
        [COM1] = 0x3f8,
        [COM2] = 0x2f8,
        [COM3] = 0x3e8,
        [COM4] = 0x2e8,
};

/**
 * Select UART port
 *
 * @v uart              UART
 * @v port              Port number, or 0 to disable
 * @ret rc              Return status code
 */
int uart_select ( struct uart *uart, unsigned int port ) {
        int rc;

        /* Set new UART base */
        if ( port >= ( sizeof ( uart_base ) / sizeof ( uart_base[0] ) ) ) {
                rc = -ENODEV;
                goto err;
        }
        uart->base = ( ( void * ) ( intptr_t ) uart_base[port] );

        /* Check that UART exists */
        if ( ( rc = uart_exists ( uart ) ) != 0 )
                goto err;

        return 0;

 err:
        uart->base = NULL;
        return rc;
}