Move {show,set,clear}_setting() to {show,set,clear}_named_setting().

Introduce new {show,set,clear}_setting() that take a struct setting *
rather than a const char *.

set_setting() handles calling clear_setting() when appropriate, so that
individual setting types don't have to check for empty strings.

src/core/settings.c

 }
 
 /**
- * Show value of setting
+ * Show value of named setting
  *
  * @v context		Configuration context
  * @v name		Configuration setting name
  * @v len		Length of buffer
  * @ret rc		Return status code
  */
-int show_setting ( struct config_context *context, const char *name,
-		   char *buf, size_t len ) {
+int show_named_setting ( struct config_context *context, const char *name,
+			 char *buf, size_t len ) {
 	struct config_setting *setting;
 	struct config_setting tmp_setting;
 
 	setting = find_or_build_config_setting ( name, &tmp_setting );
 	if ( ! setting )
 		return -ENOENT;
-	return setting->type->show ( context, setting, buf, len );
+	return show_setting ( context, setting, buf, len );
 }
 
 /**
- * Set value of setting
+ * Set value of named setting
  *
  * @v context		Configuration context
  * @v name		Configuration setting name
  * @v value		Setting value (as a string)
  * @ret rc		Return status code
  */
-int set_setting ( struct config_context *context, const char *name,
-		  const char *value ) {
+int set_named_setting ( struct config_context *context, const char *name,
+			const char *value ) {
 	struct config_setting *setting;
 	struct config_setting tmp_setting;
 
 }
 
 /**
- * Clear setting
+ * Set value of setting
  *
  * @v context		Configuration context
- * @v name		Configuration setting name
+ * @v setting		Configuration setting
+ * @v value		Setting value (as a string), or NULL
  * @ret rc		Return status code
  */
-int clear_setting ( struct config_context *context, const char *name ) {
-	struct config_setting *setting;
-	struct config_setting tmp_setting;
-
-	setting = find_or_build_config_setting ( name, &tmp_setting );
-	if ( ! setting )
-		return -ENOENT;
-
-	/* All types of settings get cleared the same way */
-	delete_dhcp_option ( context->options, setting->tag );
-
-	return 0;
+int set_setting ( struct config_context *context,
+		  struct config_setting *setting,
+		  const char *value ) {
+	if ( ( ! value ) || ( ! *value ) ) {
+		/* Save putting deletion logic in each individual handler */
+		return clear_setting ( context, setting );
+	}
+	return setting->type->set ( context, setting, value );
 }
 
 /**
 		      const char *value ) {
 	struct dhcp_option *option;
 	struct in_addr ipv4;
-	int rc;
 	
 	if ( inet_aton ( value, &ipv4 ) == 0 )
 		return -EINVAL;

src/hci/commands/nvo_cmd.c

 	}
 
 	dummy_context.options = ugly_nvo_hack->options;
-	if ( ( rc = show_setting ( &dummy_context, argv[1], buf,
-				   sizeof ( buf ) ) ) != 0 ) {
+	if ( ( rc = show_named_setting ( &dummy_context, argv[1], buf,
+					 sizeof ( buf ) ) ) != 0 ) {
 		printf ( "Could not find \"%s\": %s\n",
 			 argv[1], strerror ( -rc ) );
 		return 1;
 	}
 
 	dummy_context.options = ugly_nvo_hack->options;
-	if ( ( rc = set_setting ( &dummy_context, argv[1], argv[2] ) ) != 0 ) {
+	if ( ( rc = set_named_setting ( &dummy_context, argv[1],
+					argv[2] ) ) != 0 ) {
 		printf ( "Could not set \"%s\"=\"%s\": %s\n",
 			 argv[1], argv[2], strerror ( -rc ) );
 		return 1;
 	}
 
 	dummy_context.options = ugly_nvo_hack->options;
-	if ( ( rc = clear_setting ( &dummy_context, argv[1] ) ) != 0 ) {
+	if ( ( rc = clear_named_setting ( &dummy_context, argv[1] ) ) != 0 ) {
 		printf ( "Could not clear \"%s\": %s\n",
 			 argv[1], strerror ( -rc ) );
 		return 1;

src/hci/tui/settings_ui.c

 	widget->editing = 0;
 
 	/* Read current setting value */
-	if ( widget->setting->type->show ( widget->context, widget->setting,
-					   widget->value,
-					   sizeof ( widget->value ) ) != 0 ) {
+	if ( show_setting ( widget->context, widget->setting,
+			    widget->value, sizeof ( widget->value ) ) != 0 ) {
 		widget->value[0] = '\0';
 	}	
 
  * @v widget		Setting widget
  */
 static int save_setting ( struct setting_widget *widget ) {
-	return widget->setting->type->set ( widget->context, widget->setting,
-					    widget->value );
+	return set_setting ( widget->context, widget->setting, widget->value );
 }
 
 /**
 				if ( ( rc = save_setting ( &widget ) ) != 0 ) {
 					alert ( " Could not set %s: %s ",
 						widget.setting->name,
-						strerror ( -rc ) );
+						strerror ( rc ) );
 				}
 				/* Fall through */
 			case 0x03: /* Ctrl-C */

src/include/gpxe/settings.h

 /** Declare a configuration setting */
 #define	__config_setting __table ( config_settings, 01 )
 
-/* Function prototypes */
+/**
+ * Show value of setting
+ *
+ * @v context		Configuration context
+ * @v setting		Configuration setting
+ * @v buf		Buffer to contain value
+ * @v len		Length of buffer
+ * @ret rc		Return status code
+ */
+static inline int show_setting ( struct config_context *context,
+				 struct config_setting *setting,
+				 char *buf, size_t len ) {
+	return setting->type->show ( context, setting, buf, len );
+}
 
-extern int show_setting ( struct config_context *context, const char *name,
-			  char *buf, size_t len );
-extern int set_setting ( struct config_context *context, const char *name,
+extern int set_setting ( struct config_context *context,
+			 struct config_setting *setting,
 			 const char *value );
-extern int clear_setting ( struct config_context *context, const char *name );
+
+/**
+ * Clear setting
+ *
+ * @v context		Configuration context
+ * @v setting		Configuration setting
+ * @ret rc		Return status code
+ */
+static inline int clear_setting ( struct config_context *context,
+				  struct config_setting *setting ) {
+	delete_dhcp_option ( context->options, setting->tag );
+	return 0;
+}
+
+/* Function prototypes */
+extern int show_named_setting ( struct config_context *context,
+				const char *name, char *buf, size_t len );
+extern int set_named_setting ( struct config_context *context,
+			       const char *name, const char *value );
+
+/**
+ * Clear named setting
+ *
+ * @v context		Configuration context
+ * @v name		Configuration setting name
+ * @ret rc		Return status code
+ */
+static inline int clear_named_setting ( struct config_context *context,
+					const char *name ) {
+	return set_named_setting ( context, name, NULL );
+}
 
 #endif /* _GPXE_SETTINGS_H */