[settings] Eliminate settings "tag magic"

Create an explicit concept of "settings scope" and eliminate the magic
values used for numerical setting tags.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

3 files changed, 46 insertions, 82 deletions

diff --git a/src/include/ipxe/net80211.h b/src/include/ipxe/net80211.h
index 771872c82..dd8bd2288 100644
--- a/src/include/ipxe/net80211.h
+++ b/src/include/ipxe/net80211.h
@@ -1183,25 +1183,4 @@ static inline u16 net80211_cts_duration ( struct net80211_device *dev,
 		 net80211_duration ( dev, size, dev->rates[dev->rate] ) );
 }
 
-/** 802.11 device setting tag magic */
-#define NET80211_SETTING_TAG_MAGIC 0x8211
-
-/**
- * Construct 802.11 setting tag
- *
- * @v id		Unique identifier
- * @ret tag		Setting tag
- */
-#define NET80211_SETTING_TAG( id ) \
-	NETDEV_SETTING_TAG ( ( NET80211_SETTING_TAG_MAGIC << 8 ) | (id) )
-
-/** SSID setting tag */
-#define NET80211_SETTING_TAG_SSID NET80211_SETTING_TAG ( 0x01 )
-
-/** Active scanning setting tag */
-#define NET80211_SETTING_TAG_ACTIVE_SCAN NET80211_SETTING_TAG ( 0x02 )
-
-/** Wireless key setting tag */
-#define NET80211_SETTING_TAG_KEY NET80211_SETTING_TAG ( 0x03 )
-
 #endif
diff --git a/src/include/ipxe/netdevice.h b/src/include/ipxe/netdevice.h
index 21754fe67..0daa1d626 100644
--- a/src/include/ipxe/netdevice.h
+++ b/src/include/ipxe/netdevice.h
@@ -411,38 +411,6 @@ struct net_driver {
 /** Declare a network driver */
 #define __net_driver __table_entry ( NET_DRIVERS, 01 )
 
-/** Network device setting tag magic
- *
- * All DHCP option settings are deemed to be valid as network device
- * settings.  There are also some extra non-DHCP settings (such as
- * "mac"), which are marked as being valid network device settings by
- * using a magic tag value.
- */
-#define NETDEV_SETTING_TAG_MAGIC 0xeb
-
-/**
- * Construct network device setting tag
- *
- * @v id		Unique identifier
- * @ret tag		Setting tag
- */
-#define NETDEV_SETTING_TAG( id ) ( ( NETDEV_SETTING_TAG_MAGIC << 24 ) | (id) )
-
-/**
- * Check if tag is a network device setting tag
- *
- * @v tag		Setting tag
- * @ret is_ours		Tag is a network device setting tag
- */
-#define IS_NETDEV_SETTING_TAG( tag ) \
-	( ( (tag) >> 24 ) == NETDEV_SETTING_TAG_MAGIC )
-
-/** MAC address setting tag */
-#define NETDEV_SETTING_TAG_MAC NETDEV_SETTING_TAG ( 0x01 )
-
-/** Bus ID setting tag */
-#define NETDEV_SETTING_TAG_BUS_ID NETDEV_SETTING_TAG ( 0x02 )
-
 extern struct list_head net_devices;
 extern struct net_device_operations null_netdev_operations;
 extern struct settings_operations netdev_settings_operations;
diff --git a/src/include/ipxe/settings.h b/src/include/ipxe/settings.h
index 3f8876020..9b7404ac2 100644
--- a/src/include/ipxe/settings.h
+++ b/src/include/ipxe/settings.h
@@ -38,27 +38,14 @@ struct setting {
 	 * The setting tag is a numerical description of the setting
 	 * (such as a DHCP option number, or an SMBIOS structure and
 	 * field number).
-	 *
-	 * Users can construct tags for settings that are not
-	 * explicitly known to iPXE using the generic syntax for
-	 * numerical settings.  For example, the setting name "60"
-	 * will be interpreted as referring to DHCP option 60 (the
-	 * vendor class identifier).
-	 *
-	 * This creates a potential for namespace collisions, since
-	 * the interpretation of the numerical description will vary
-	 * according to the settings block.  When a user attempts to
-	 * fetch a generic numerical setting, we need to ensure that
-	 * only the intended settings block interprets the numerical
-	 * description.  (For example, we do not want to attempt to
-	 * retrieve the subnet mask from SMBIOS, or the system UUID
-	 * from DHCP.)
-	 *
-	 * This potential problem is resolved by allowing the setting
-	 * tag to include a "magic" value indicating the
-	 * interpretation to be placed upon the numerical description.
 	 */
 	unsigned int tag;
+	/** Setting scope (or NULL)
+	 *
+	 * For historic reasons, a NULL scope with a non-zero tag
+	 * indicates a DHCPv4 option setting.
+	 */
+	struct settings_scope *scope;
 };
 
 /** Configuration setting table */
@@ -134,12 +121,6 @@ struct settings {
 	struct refcnt *refcnt;
 	/** Name */
 	const char *name;
-	/** Tag magic
-	 *
-	 * This value will be ORed in to any numerical tags
-	 * constructed by parse_setting_name().
-	 */
-	unsigned int tag_magic;
 	/** Parent settings block */
 	struct settings *parent;
 	/** Sibling settings blocks */
@@ -148,9 +129,45 @@ struct settings {
 	struct list_head children;
 	/** Settings block operations */
 	struct settings_operations *op;
+	/** Default scope for numerical settings constructed for this block */
+	struct settings_scope *default_scope;
 };
 
 /**
+ * A setting scope
+ *
+ * Users can construct tags for settings that are not explicitly known
+ * to iPXE using the generic syntax for numerical settings.  For
+ * example, the setting name "60" will be interpreted as referring to
+ * DHCP option 60 (the vendor class identifier).
+ *
+ * This creates a potential for namespace collisions, since the
+ * interpretation of the numerical description will vary according to
+ * the settings block.  When a user attempts to fetch a generic
+ * numerical setting, we need to ensure that only the intended
+ * settings blocks interpret this numerical description.  (For
+ * example, we do not want to attempt to retrieve the subnet mask from
+ * SMBIOS, or the system UUID from DHCP.)
+ *
+ * This potential problem is resolved by including a user-invisible
+ * "scope" within the definition of each setting.  Settings blocks may
+ * use this to determine whether or not the setting is applicable.
+ * Any settings constructed from a numerical description
+ * (e.g. "smbios/1.4.0") will be assigned the default scope of the
+ * settings block specified in the description (e.g. "smbios"); this
+ * provides behaviour matching the user's expectations in most
+ * circumstances.
+ */
+struct settings_scope {
+	/** Dummy field
+	 *
+	 * This is included only to ensure that pointers to different
+	 * scopes always compare differently.
+	 */
+	uint8_t dummy;
+} __attribute__ (( packed ));
+
+/**
  * A setting type
  *
  * This represents a type of setting (e.g. string, IPv4 address,
@@ -329,17 +346,17 @@ extern struct setting busid_setting __setting ( SETTING_NETDEV );
  * @v settings		Settings block
  * @v op		Settings block operations
  * @v refcnt		Containing object reference counter, or NULL
- * @v tag_magic		Tag magic
+ * @v default_scope	Default scope
  */
 static inline void settings_init ( struct settings *settings,
 				   struct settings_operations *op,
 				   struct refcnt *refcnt,
-				   unsigned int tag_magic ) {
+				   struct settings_scope *default_scope ) {
 	INIT_LIST_HEAD ( &settings->siblings );
 	INIT_LIST_HEAD ( &settings->children );
 	settings->op = op;
 	settings->refcnt = refcnt;
-	settings->tag_magic = tag_magic;
+	settings->default_scope = default_scope;
 }
 
 /**
@@ -351,7 +368,7 @@ static inline void settings_init ( struct settings *settings,
 static inline void generic_settings_init ( struct generic_settings *generics,
 					   struct refcnt *refcnt ) {
 	settings_init ( &generics->settings, &generic_settings_operations,
-			refcnt, 0 );
+			refcnt, NULL );
 	INIT_LIST_HEAD ( &generics->list );
 }