A patch to include a small program that reads from/to physical memory.
Useful for e.g. tuning the processor register map after bootup.

I put in util-linux.

-- 
  greetz, marc
Is everybody aboard this ship kinkoid?
        Chiana - A Bug's Life
chiana 2.6.18-4-ixp4xx #1 Tue Mar 27 18:01:56 BST 2007 GNU/Linux
---
 include/applets.h    |    1 
 include/usage.h      |   10 ++++
 util-linux/Config.in |    7 +++
 util-linux/Kbuild    |    1 
 util-linux/devmem2.c |  106 +++++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 125 insertions(+)

Index: busybox-1.6.1/include/applets.h
===================================================================
--- busybox-1.6.1.orig/include/applets.h
+++ busybox-1.6.1/include/applets.h
@@ -111,6 +111,7 @@
 USE_DELGROUP(APPLET_ODDNAME(delgroup, deluser, _BB_DIR_BIN, _BB_SUID_NEVER, delgroup))
 USE_DELUSER(APPLET(deluser, _BB_DIR_BIN, _BB_SUID_NEVER))
 USE_DEVFSD(APPLET(devfsd, _BB_DIR_SBIN, _BB_SUID_NEVER))
+USE_DEVMEM2(APPLET(devmem2, _BB_DIR_SBIN, _BB_SUID_NEVER))
 USE_DF(APPLET(df, _BB_DIR_BIN, _BB_SUID_NEVER))
 USE_APP_DHCPRELAY(APPLET(dhcprelay, _BB_DIR_USR_SBIN, _BB_SUID_NEVER))
 USE_DIFF(APPLET(diff, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
Index: busybox-1.6.1/include/usage.h
===================================================================
--- busybox-1.6.1.orig/include/usage.h
+++ busybox-1.6.1/include/usage.h
@@ -603,6 +603,16 @@
        "\n		and processing synthetic REGISTER events," \
        "\n		do not poll for events")
 
+#define devmem2_trivial_usage \
+	"devmem2 { address } [ type [ data ] ]"
+
+#define devmem2_full_usage \
+	"Read/Write from physical addresses" \
+	"\n\nUsage:  devmem2 { address } [ type [ data ] ]" \
+        "\n	address : memory address to act upon" \
+	"\n	type    : access operation type : [b]yte, [h]alfword, [w]ord" \
+	"\n	data    : data to be written"
+
 #define df_trivial_usage \
        "[-" USE_FEATURE_HUMAN_READABLE("hm") "k] [FILESYSTEM ...]"
 #define df_full_usage \
Index: busybox-1.6.1/util-linux/Config.in
===================================================================
--- busybox-1.6.1.orig/util-linux/Config.in
+++ busybox-1.6.1/util-linux/Config.in
@@ -5,6 +5,13 @@
 
 menu "Linux System Utilities"
 
+config DEVMEM2
+	bool "devmem2"
+	default n
+	help
+	  devmem2 is a small program that reads and writes from physcial
+	  memory using /dev/mem.
+
 config DMESG
 	bool "dmesg"
 	default n
Index: busybox-1.6.1/util-linux/Kbuild
===================================================================
--- busybox-1.6.1.orig/util-linux/Kbuild
+++ busybox-1.6.1/util-linux/Kbuild
@@ -30,3 +30,4 @@
 lib-$(CONFIG_SWAPONOFF)		+=swaponoff.o
 lib-$(CONFIG_SWITCH_ROOT)	+=switch_root.o
 lib-$(CONFIG_UMOUNT)		+=umount.o
+lib-$(CONFIG_DEVMEM2)		+=devmem2.o
Index: busybox-1.6.1/util-linux/devmem2.c
===================================================================
--- /dev/null
+++ busybox-1.6.1/util-linux/devmem2.c
@@ -0,0 +1,106 @@
+/*
+ * devmem2.c: Simple program to read/write from/to any location in memory.
+ *
+ *  Copyright (C) 2000, Jan-Derk Bakker ([EMAIL PROTECTED])
+ *  Include in busybox by Marc Leeman ([EMAIL PROTECTED])
+ *
+ * This software has been developed for the LART computing board
+ * (http://www.lart.tudelft.nl/). The development has been sponsored by
+ * the Mobile MultiMedia Communications (http://www.mmc.tudelft.nl/)
+ * and Ubiquitous Communications (http://www.ubicom.tudelft.nl/)
+ * projects.
+ *
+ *
+ * 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 "libbb.h"
+
+#define FATAL do { bb_perror_msg_and_die("Error at line %d, file %s (%d) [%s]\n", \
+  __LINE__, __FILE__, errno, strerror(errno)); exit(1); } while(0)
+
+#define MAP_SIZE 4096UL
+#define MAP_MASK (MAP_SIZE - 1)
+
+int devmem2_main(int argc, char **argv);
+int devmem2_main(int argc, char **argv) {
+    int fd;
+    void *map_base, *virt_addr;
+	unsigned long read_result, writeval;
+	off_t target;
+	int access_type = 'w';
+
+	if(argc < 2) {
+		 bb_show_usage();
+	}
+	target = strtoul(argv[1], 0, 0);
+
+	if(argc > 2)
+		access_type = tolower(argv[2][0]);
+
+
+    if((fd = xopen("/dev/mem", O_RDWR | O_SYNC)) == -1) FATAL;
+    printf("/dev/mem opened.\n");
+    fflush(stdout);
+
+    /* Map one page */
+    map_base = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, target & ~MAP_MASK);
+    if(map_base == (void *) -1) FATAL;
+    printf("Memory mapped at address %p.\n", map_base);
+    fflush(stdout);
+
+    virt_addr = map_base + (target & MAP_MASK);
+    switch(access_type) {
+		case 'b':
+			read_result = *((unsigned char *) virt_addr);
+			break;
+		case 'h':
+			read_result = *((unsigned short *) virt_addr);
+			break;
+		case 'w':
+			read_result = *((unsigned long *) virt_addr);
+			break;
+		default:
+			bb_perror_msg_and_die("Illegal data type '%c'.\n", access_type);
+	}
+    printf("Value at address 0x%lx (%p): 0x%lx\n", target, virt_addr, read_result);
+    fflush(stdout);
+
+	if(argc > 3) {
+		writeval = strtoul(argv[3], 0, 0);
+		switch(access_type) {
+			case 'b':
+				*((unsigned char *) virt_addr) = writeval;
+				read_result = *((unsigned char *) virt_addr);
+				break;
+			case 'h':
+				*((unsigned short *) virt_addr) = writeval;
+				read_result = *((unsigned short *) virt_addr);
+				break;
+			case 'w':
+				*((unsigned long *) virt_addr) = writeval;
+				read_result = *((unsigned long *) virt_addr);
+				break;
+		}
+		printf("Written 0x%lx; readback 0x%lx\n", writeval, read_result);
+		fflush(stdout);
+	}
+
+	if(munmap(map_base, MAP_SIZE) == -1) FATAL;
+    close(fd);
+    return 0;
+}
+

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