dmidecode: Add --no-sysfs option to disable use of sysfs

This option forces any SMBIOS information in sysfs to be ignored, resulting
in dmidecode using /dev/mem for SMBIOS access.  This is likely most useful
for debugging.

Contributed by Roy Franz.

Author: jdelvare

CHANGELOG

@@ -4,6 +4,9 @@
 	  entire binary file into a buffer.
 	* dmidecode.c: Add passing of flags parameter to dmi_table.
 	* dmidecode.c: Add reading of SMBIOS tables from sysfs.
+	* dmidecode.c, dmiopt.c, dmiopt.h: Add --no-sysfs option to disable
+	  use of sysfs.
+	* dmidecode.8: Document the changes above.
 
 2015-04-20  Jean Delvare  <[email protected]>
 

dmidecode.c

@@ -4677,7 +4677,8 @@ int main(int argc, char * const argv[])
 	 * contain one of several types of entry points, so read enough for
 	 * the largest one, then determine what type it contains.
 	 */
-	if ((buf = read_file(0x20, SYS_ENTRY_FILE)) != NULL)
+	if (!(opt.flags & FLAG_NO_SYSFS)
+	 && (buf = read_file(0x20, SYS_ENTRY_FILE)) != NULL)
 	{
 		if (!(opt.flags & FLAG_QUIET))
 			printf("Getting SMBIOS data from sysfs.\n");

dmiopt.c

@@ -225,6 +225,7 @@ int parse_command_line(int argc, char * const argv[])
 		{ "dump", no_argument, NULL, 'u' },
 		{ "dump-bin", required_argument, NULL, 'B' },
 		{ "from-dump", required_argument, NULL, 'F' },
+		{ "no-sysfs", no_argument, NULL, 'S' },
 		{ "version", no_argument, NULL, 'V' },
 		{ 0, 0, 0, 0 }
 	};
@@ -262,6 +263,9 @@ int parse_command_line(int argc, char * const argv[])
 			case 'u':
 				opt.flags |= FLAG_DUMP;
 				break;
+			case 'S':
+				opt.flags |= FLAG_NO_SYSFS;
+				break;
 			case 'V':
 				opt.flags |= FLAG_VERSION;
 				break;

dmiopt.h

@@ -42,6 +42,7 @@ extern struct opt opt;
 #define FLAG_QUIET              (1 << 3)
 #define FLAG_DUMP_BIN           (1 << 4)
 #define FLAG_FROM_DUMP          (1 << 5)
+#define FLAG_NO_SYSFS           (1 << 6)
 
 int parse_command_line(int argc, char * const argv[]);
 void print_help(void);

man/dmidecode.8

@@ -130,6 +130,10 @@ later.
 Read the DMI data from a binary file previously generated using 
 \fB--dump-bin\fR.
 .TP
+.BR "  " "  " "--no-sysfs"
+Do not attempt to read DMI data from sysfs files. This is mainly useful for
+debugging.
+.TP
 .BR "-h" ", " "--help"
 Display usage information and exit
 .TP