wireless: fixup genregdb.awk for remove of antenna gain from wireless-regd

Since "wireless-regdb: remove antenna gain" was merged in the
wireless-regdb tree, the awk script parser has been incompatible
with the 'official' regulatory database.  This fixes that up.
Without this change the max EIRP is set to 0 making 802.11 devices
useless.

The fragile nature of the awk parser must be replaced, but ideas
over how to do that in the most scalable way are being reviewed.
In the meantime update the documentation for CFG80211_INTERNAL_REGDB
so folks are aware of expectations for now.
Reported-by: John Walker <john@x109.net>
Reported-by: Krishna Chaitanya <chaitanya.mgit@gmail.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/Kconfig

@@ -162,6 +162,12 @@ config CFG80211_INTERNAL_REGDB
 	  and includes code to query that database.  This is an alternative
 	  to using CRDA for defining regulatory rules for the kernel.
 
+	  Using this option requires some parsing of the db.txt at build time,
+	  the parser will be upkept with the latest wireless-regdb updates but
+	  older wireless-regdb formats will be ignored. The parser may later
+	  be replaced to avoid issues with conflicts on versions of
+	  wireless-regdb.
+
 	  For details see:
 
 	  http://wireless.kernel.org/en/developers/Regulatory

net/wireless/genregdb.awk

@@ -51,32 +51,41 @@ function parse_country_head() {
 
 function parse_reg_rule()
 {
+	flag_starts_at = 7
+
 	start = $1
 	sub(/\(/, "", start)
 	end = $3
 	bw = $5
 	sub(/\),/, "", bw)
-	gain = $6
-	sub(/\(/, "", gain)
-	sub(/,/, "", gain)
-	power = $7
-	sub(/\)/, "", power)
-	sub(/,/, "", power)
+	gain = 0
+	power = $6
 	# power might be in mW...
-	units = $8
+	units = $7
+	dfs_cac = 0
+
+	sub(/\(/, "", power)
+	sub(/\),/, "", power)
+	sub(/\),/, "", units)
 	sub(/\)/, "", units)
-	sub(/,/, "", units)
-	dfs_cac = $9
+
 	if (units == "mW") {
+		flag_starts_at = 8
 		power = 10 * log(power)/log(10)
+		if ($8 ~ /[[:digit:]]/) {
+			flag_starts_at = 9
+			dfs_cac = $8
+		}
 	} else {
-		dfs_cac = $8
+		if ($7 ~ /[[:digit:]]/) {
+			flag_starts_at = 8
+			dfs_cac = $7
+		}
 	}
-	sub(/,/, "", dfs_cac)
 	sub(/\(/, "", dfs_cac)
-	sub(/\)/, "", dfs_cac)
+	sub(/\),/, "", dfs_cac)
 	flagstr = ""
-	for (i=8; i<=NF; i++)
+	for (i=flag_starts_at; i<=NF; i++)
 		flagstr = flagstr $i
 	split(flagstr, flagarray, ",")
 	flags = ""