Added basic infrastructure for manipulating settings.

src/include/gpxe/settings.h

@@ -0,0 +1,103 @@
+#ifndef _GPXE_SETTINGS_H
+#define _GPXE_SETTINGS_H
+
+/** @file
+ *
+ * Configuration settings
+ *
+ */
+
+#include <stdint.h>
+#include <gpxe/dhcp.h>
+#include <gpxe/tables.h>
+
+struct config_setting;
+
+/**
+ * A configuration context
+ *
+ * This identifies the context within which settings are inspected and
+ * changed.  For example, the context might be global, or might be
+ * restricted to the settings stored in NVS on a particular device.
+ */
+struct config_context {
+	/** DHCP options block, or NULL
+	 *
+	 * If NULL, all registered DHCP options blocks will be used.
+	 */
+	struct dhcp_option_block *options;
+};
+
+/**
+ * A configuration setting type
+ *
+ * This represents a type of configuration setting (e.g. string, IPv4
+ * address, etc.).
+ */
+struct config_setting_type {
+	/** Name
+	 *
+	 * This is the name exposed to the user (e.g. "string").
+	 */
+	const char *name;
+	/** Show value of setting
+	 *
+	 * @v context		Configuration context
+	 * @v setting		Configuration setting
+	 * @ret value		Setting value (as a string), or NULL
+	 */
+	const char * ( * show ) ( struct config_context *context,
+				  struct config_setting *setting );
+	/** Set value of setting
+	 *
+	 * @v context		Configuration context
+	 * @v setting		Configuration setting
+	 * @v value		Setting value (as a string)
+	 * @ret rc		Return status code
+	 */ 
+	int ( * set ) ( struct config_context *context,
+			struct config_setting *setting,
+			const char *value );
+};
+
+/** Declare a configuration setting type */
+#define	__config_setting_type __table ( config_setting_types, 01 )
+
+/**
+ * A configuration setting
+ *
+ * This represents a single configuration setting (e.g. "hostname").
+ */
+struct config_setting {
+	/** Name
+	 *
+	 * This is the human-readable name for the setting.  Where
+	 * possible, it should match the name used in dhcpd.conf (see
+	 * dhcp-options(5)).
+	 */
+	const char *name;
+	/** DHCP option tag
+	 *
+	 * This is the DHCP tag used to identify the option in DHCP
+	 * packets and stored option blocks.
+	 */
+	unsigned int tag;
+	/** Configuration setting type
+	 *
+	 * This identifies the type of setting (e.g. string, IPv4
+	 * address, etc.).
+	 */
+	struct config_setting_type *type;
+};
+
+/** Declare a configuration setting */
+#define	__config_setting __table ( config_settings, 01 )
+
+/* Function prototypes */
+
+extern const char * ( show_setting ) ( struct config_context *context,
+				       const char *name );
+extern int ( set_setting ) ( struct config_context *context, const char *name,
+			     const char *value );
+
+#endif /* _GPXE_SETTINGS_H */