iPXE
x86_uart.c
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00001 /*
00002  * Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
00003  *
00004  * This program is free software; you can redistribute it and/or
00005  * modify it under the terms of the GNU General Public License as
00006  * published by the Free Software Foundation; either version 2 of the
00007  * License, or any later version.
00008  *
00009  * This program is distributed in the hope that it will be useful, but
00010  * WITHOUT ANY WARRANTY; without even the implied warranty of
00011  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00012  * General Public License for more details.
00013  *
00014  * You should have received a copy of the GNU General Public License
00015  * along with this program; if not, write to the Free Software
00016  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
00017  * 02110-1301, USA.
00018  *
00019  * You can also choose to distribute this program under the terms of
00020  * the Unmodified Binary Distribution Licence (as given in the file
00021  * COPYING.UBDL), provided that you have satisfied its requirements.
00022  */
00023 
00024 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
00025 
00026 /** @file
00027  *
00028  * 16550-compatible UART
00029  *
00030  */
00031 
00032 #include <errno.h>
00033 #include <ipxe/uart.h>
00034 
00035 /** UART port bases */
00036 static uint16_t uart_base[] = {
00037         [COM1] = 0x3f8,
00038         [COM2] = 0x2f8,
00039         [COM3] = 0x3e8,
00040         [COM4] = 0x2e8,
00041 };
00042 
00043 /**
00044  * Select UART port
00045  *
00046  * @v uart              UART
00047  * @v port              Port number, or 0 to disable
00048  * @ret rc              Return status code
00049  */
00050 int uart_select ( struct uart *uart, unsigned int port ) {
00051         int rc;
00052 
00053         /* Set new UART base */
00054         if ( port >= ( sizeof ( uart_base ) / sizeof ( uart_base[0] ) ) ) {
00055                 rc = -ENODEV;
00056                 goto err;
00057         }
00058         uart->base = ( ( void * ) ( intptr_t ) uart_base[port] );
00059 
00060         /* Check that UART exists */
00061         if ( ( rc = uart_exists ( uart ) ) != 0 )
00062                 goto err;
00063 
00064         return 0;
00065 
00066  err:
00067         uart->base = NULL;
00068         return rc;
00069 }