[settings] Display canonical setting name in output of "show" command

Enable the "show" command to display the full, canonicalised name of
the fetched setting.  For example:

  iPXE> show mac
  net0/mac:hex = 52:54:00:12:34:56

  iPXE> dhcp && show ip
  DHCP (net0 52:54:00:12:34:56)... ok
  net0.dhcp/ip:ipv4 = 10.0.0.168

  iPXE> show net0/6
  net0.dhcp/dns:ipv4 = 10.0.0.6

Inspired-by: Glenn Brown <glenn@myri.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/settings.c

 	char *setting_name;
 	char *type_name;
 	struct setting *named_setting;
-	unsigned int tag;
 
 	/* Set defaults */
 	*settings = &settings_root;
 	}
 
 	/* Identify setting */
-	if ( ( named_setting = find_setting ( setting_name ) ) != NULL ) {
+	setting->tag = parse_setting_tag ( *settings, setting_name );
+	setting->name = setting_name;
+	for_each_table_entry ( named_setting, SETTINGS ) {
 		/* Matches a defined named setting; use that setting */
-		memcpy ( setting, named_setting, sizeof ( *setting ) );
-	} else if ( ( tag = parse_setting_tag ( *settings,
-						setting_name ) ) != 0 ) {
-		/* Is a valid numeric tag; use the tag */
-		setting->tag = tag;
-	} else {
-		/* Use the arbitrary name */
-		setting->name = setting_name;
+		if ( setting_cmp ( named_setting, setting ) == 0 ) {
+			memcpy ( setting, named_setting, sizeof ( *setting ) );
+			break;
+		}
 	}
 
 	/* Identify setting type, if specified */
 	char tmp_name[ strlen ( name ) + 1 ];
 	int rc;
 
+	/* Parse setting name */
 	if ( ( rc = parse_setting_name ( name, autovivify_child_settings,
 					 &settings, &setting, tmp_name )) != 0)
 		return rc;
-	return storef_setting ( settings, &setting, value );
+
+	/* Store setting */
+	if ( ( rc = storef_setting ( settings, &setting, value ) ) != 0 )
+		return rc;
+
+	return 0;
 }
 
 /**
  * Fetch and format value of named setting
  *
  * @v name		Name of setting
- * @v buf		Buffer to contain formatted value
- * @v len		Length of buffer
+ * @v name_buf		Buffer to contain canonicalised name
+ * @v name_len		Length of canonicalised name buffer
+ * @v value_buf		Buffer to contain formatted value
+ * @v value_len		Length of formatted value buffer
  * @ret len		Length of formatted value, or negative error
  */
-int fetchf_named_setting ( const char *name, char *buf, size_t len ) {
+int fetchf_named_setting ( const char *name,
+			   char *name_buf, size_t name_len,
+			   char *value_buf, size_t value_len ) {
 	struct settings *settings;
 	struct setting setting;
+	struct settings *origin;
+	const char *origin_name;
 	char tmp_name[ strlen ( name ) + 1 ];
 	int rc;
 
+	/* Parse setting name */
 	if ( ( rc = parse_setting_name ( name, find_child_settings,
 					 &settings, &setting, tmp_name )) != 0)
 		return rc;
-	return fetchf_setting ( settings, &setting, buf, len );
+
+	/* Fetch setting */
+	if ( ( rc = fetchf_setting ( settings, &setting, value_buf,
+				     value_len ) ) < 0 )
+		return rc;
+
+	/* Construct setting name */
+	origin = fetch_setting_origin ( settings, &setting );
+	assert ( origin != NULL );
+	origin_name = settings_name ( origin );
+	snprintf ( name_buf, name_len, "%s%s%s:%s",
+		   origin_name, ( origin_name[0] ? "/" : "" ),
+		   setting.name, setting.type->name );
+
+	return 0;
 }
 
 /******************************************************************************
 		tail = ( end + 1 );
 
 		/* Determine setting length */
-		setting_len = fetchf_named_setting ( name, NULL, 0 );
+		setting_len = fetchf_named_setting ( name, NULL, 0, NULL, 0 );
 		if ( setting_len < 0 )
 			setting_len = 0; /* Treat error as empty setting */
 
 			char setting_buf[ setting_len + 1 ];
 
 			setting_buf[0] = '\0';
-			fetchf_named_setting ( name, setting_buf,
+			fetchf_named_setting ( name, NULL, 0, setting_buf,
 					       sizeof ( setting_buf ) );
 
 			/* Construct expanded string and discard old string */

src/hci/commands/nvo_cmd.c

 static int show_exec ( int argc, char **argv ) {
 	struct show_options opts;
 	const char *name;
-	char buf[256];
+	char name_buf[32];
+	char value_buf[256];
 	int rc;
 
 	/* Parse options */
 	name = argv[optind];
 
 	/* Fetch setting */
-	if ( ( rc = fetchf_named_setting ( name, buf,
-					   sizeof ( buf ) ) ) < 0 ) {
+	if ( ( rc = fetchf_named_setting ( name, name_buf, sizeof ( name_buf ),
+					   value_buf,
+					   sizeof ( value_buf ) ) ) < 0 ) {
 		printf ( "Could not find \"%s\": %s\n",
 			 name, strerror ( rc ) );
 		return rc;
 	}
 
 	/* Print setting value */
-	printf ( "%s = %s\n", name, buf );
+	printf ( "%s = %s\n", name_buf, value_buf );
 
 	return 0;
 }

src/include/ipxe/settings.h

 			    struct setting *setting,
 			    const char *value );
 extern int storef_named_setting ( const char *name, const char *value );
-extern int fetchf_named_setting ( const char *name, char *buf, size_t len );
+extern int fetchf_named_setting ( const char *name, char *name_buf,
+				  size_t name_len, char *value_buf,
+				  size_t value_len );
 extern char * expand_settings ( const char *string );
 
 extern struct setting_type setting_type_string __setting_type;