IOMUX: Add console multiplexing support.

Modifications to support console multiplexing.  This is controlled using
CONFIG_SYS_CONSOLE_MUX in the board configuration file.

This allows a user to specify multiple console devices in the environment
with a command like this: setenv stdin serial,nc.  As a result, the user can
enter text on both the serial and netconsole interfaces.

All devices - stdin, stdout and stderr - can be set in this manner.

1) common/iomux.c and include/iomux.h contain the environment setting
implementation.
2) doc/README.iomux contains a somewhat more detailed description.
3) The implementation in (1) is called from common/cmd_nvedit.c to
handle setenv and from common/console.c to handle initialization of
input/output devices at boot time.
4) common/console.c also contains the code needed to poll multiple console
devices for input and send output to all devices registered for output.
5) include/common.h includes iomux.h and common/Makefile generates iomux.o
when CONFIG_SYS_CONSOLE_MUX is set.

Signed-off-by: Gary Jennejohn <garyj@denx.de>

common/iomux.c

@@ -0,0 +1,175 @@
+/*
+ * (C) Copyright 2008
+ * Gary Jennejohn, DENX Software Engineering GmbH, garyj@denx.de.
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * 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., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <common.h>
+#include <serial.h>
+#include <malloc.h>
+
+#ifdef CONFIG_CONSOLE_MUX
+void iomux_printdevs(const int console)
+{
+	int i;
+	device_t *dev;
+
+	for (i = 0; i < cd_count[console]; i++) {
+		dev = console_devices[console][i];
+		printf("%s ", dev->name);
+	}
+	printf("\n");
+}
+
+/* This tries to preserve the old list if an error occurs. */
+int iomux_doenv(const int console, const char *arg)
+{
+	char *console_args, *temp, **start;
+	int i, j, k, io_flag, cs_idx, repeat;
+	device_t *dev;
+	device_t **cons_set;
+
+	console_args = strdup(arg);
+	if (console_args == NULL)
+		return 1;
+	/*
+	 * Check whether a comma separated list of devices was
+	 * entered and count how many devices were entered.
+	 * The array start[] has pointers to the beginning of
+	 * each device name (up to MAX_CONSARGS devices).
+	 *
+	 * Have to do this twice - once to count the number of
+	 * commas and then again to populate start.
+	 */
+	i = 0;
+	temp = console_args;
+	for (;;) {
+		temp = strchr(temp, ',');
+		if (temp != NULL) {
+			i++;
+			temp++;
+			continue;
+		}
+		/* There's always one entry more than the number of commas. */
+		i++;
+		break;
+	}
+	start = (char **)malloc(i * sizeof(char *));
+	if (start == NULL) {
+		free(console_args);
+		return 1;
+	}
+	i = 0;
+	start[0] = console_args;
+	for (;;) {
+		temp = strchr(start[i++], ',');
+		if (temp == NULL)
+			break;
+		*temp = '\0';
+		start[i] = temp + 1;
+	}
+	cons_set = (device_t **)calloc(i, sizeof(device_t *));
+	if (cons_set == NULL) {
+		free(start);
+		free(console_args);
+		return 1;
+	}
+
+	switch (console) {
+	case stdin:
+		io_flag = DEV_FLAGS_INPUT;
+		break;
+	case stdout:
+	case stderr:
+		io_flag = DEV_FLAGS_OUTPUT;
+		break;
+	default:
+		free(start);
+		free(console_args);
+		free(cons_set);
+		return 1;
+	}
+
+	cs_idx = 0;
+	for (j = 0; j < i; j++) {
+		/*
+		 * Check whether the device exists and is valid.
+		 * console_assign() also calls search_device(),
+		 * but I need the pointer to the device.
+		 */
+		dev = search_device(io_flag, start[j]);
+		if (dev == NULL)
+			continue;
+		/*
+		 * Prevent multiple entries for a device.
+		 */
+		 repeat = 0;
+		 for (k = 0; k < cs_idx; k++) {
+			if (dev == cons_set[k]) {
+				repeat++;
+				break;
+			}
+		 }
+		 if (repeat)
+			continue;
+		/*
+		 * Try assigning the specified device.
+		 * This could screw up the console settings for apps.
+		 */
+		if (console_assign(console, start[j]) < 0)
+			continue;
+#ifdef CONFIG_SERIAL_MULTI
+		/*
+		 * This was taken from common/cmd_nvedit.c.
+		 * This will never work because serial_assign() returns
+		 * 1 upon error, not -1.
+		 * This would almost always return an error anyway because
+		 * serial_assign() expects the name of a serial device, like
+		 * serial_smc, but the user generally only wants to set serial.
+		 */
+		if (serial_assign(start[j]) < 0)
+			continue;
+#endif
+		cons_set[cs_idx++] = dev;
+	}
+	free(console_args);
+	free(start);
+	/* failed to set any console */
+	if (cs_idx == 0) {
+		free(cons_set);
+		return 1;
+	} else {
+		/* Works even if console_devices[console] is NULL. */
+		console_devices[console] =
+			(device_t **)realloc(console_devices[console],
+			cs_idx * sizeof(device_t *));
+		if (console_devices[console] == NULL) {
+			free(cons_set);
+			return 1;
+		}
+		memcpy(console_devices[console], cons_set, cs_idx *
+			sizeof(device_t *));
+
+		cd_count[console] = cs_idx;
+	}
+	free(cons_set);
+	return 0;
+}
+#endif /* CONFIG_CONSOLE_MUX */