+/* Helper for regdom_intersect(), this does the real
+ * mathematical intersection fun */
+static int reg_rules_intersect(
+ const struct ieee80211_reg_rule *rule1,
+ const struct ieee80211_reg_rule *rule2,
+ struct ieee80211_reg_rule *intersected_rule)
+{
+ const struct ieee80211_freq_range *freq_range1, *freq_range2;
+ struct ieee80211_freq_range *freq_range;
+ const struct ieee80211_power_rule *power_rule1, *power_rule2;
+ struct ieee80211_power_rule *power_rule;
+ u32 freq_diff;
+
+ freq_range1 = &rule1->freq_range;
+ freq_range2 = &rule2->freq_range;
+ freq_range = &intersected_rule->freq_range;
+
+ power_rule1 = &rule1->power_rule;
+ power_rule2 = &rule2->power_rule;
+ power_rule = &intersected_rule->power_rule;
+
+ freq_range->start_freq_khz = max(freq_range1->start_freq_khz,
+ freq_range2->start_freq_khz);
+ freq_range->end_freq_khz = min(freq_range1->end_freq_khz,
+ freq_range2->end_freq_khz);
+ freq_range->max_bandwidth_khz = min(freq_range1->max_bandwidth_khz,
+ freq_range2->max_bandwidth_khz);
+
+ freq_diff = freq_range->end_freq_khz - freq_range->start_freq_khz;
+ if (freq_range->max_bandwidth_khz > freq_diff)
+ freq_range->max_bandwidth_khz = freq_diff;
+
+ power_rule->max_eirp = min(power_rule1->max_eirp,
+ power_rule2->max_eirp);
+ power_rule->max_antenna_gain = min(power_rule1->max_antenna_gain,
+ power_rule2->max_antenna_gain);
+
+ intersected_rule->flags = (rule1->flags | rule2->flags);
+
+ if (!is_valid_reg_rule(intersected_rule))
+ return -EINVAL;
+
+ return 0;
+}
+
+/**
+ * regdom_intersect - do the intersection between two regulatory domains
+ * @rd1: first regulatory domain
+ * @rd2: second regulatory domain
+ *
+ * Use this function to get the intersection between two regulatory domains.
+ * Once completed we will mark the alpha2 for the rd as intersected, "98",
+ * as no one single alpha2 can represent this regulatory domain.
+ *
+ * Returns a pointer to the regulatory domain structure which will hold the
+ * resulting intersection of rules between rd1 and rd2. We will
+ * kzalloc() this structure for you.
+ */
+static struct ieee80211_regdomain *regdom_intersect(
+ const struct ieee80211_regdomain *rd1,
+ const struct ieee80211_regdomain *rd2)
+{
+ int r, size_of_regd;
+ unsigned int x, y;
+ unsigned int num_rules = 0, rule_idx = 0;
+ const struct ieee80211_reg_rule *rule1, *rule2;
+ struct ieee80211_reg_rule *intersected_rule;
+ struct ieee80211_regdomain *rd;
+ /* This is just a dummy holder to help us count */
+ struct ieee80211_reg_rule irule;
+
+ /* Uses the stack temporarily for counter arithmetic */
+ intersected_rule = &irule;
+
+ memset(intersected_rule, 0, sizeof(struct ieee80211_reg_rule));
+
+ if (!rd1 || !rd2)
+ return NULL;
+
+ /* First we get a count of the rules we'll need, then we actually
+ * build them. This is to so we can malloc() and free() a
+ * regdomain once. The reason we use reg_rules_intersect() here
+ * is it will return -EINVAL if the rule computed makes no sense.
+ * All rules that do check out OK are valid. */
+
+ for (x = 0; x < rd1->n_reg_rules; x++) {
+ rule1 = &rd1->reg_rules[x];
+ for (y = 0; y < rd2->n_reg_rules; y++) {
+ rule2 = &rd2->reg_rules[y];
+ if (!reg_rules_intersect(rule1, rule2,
+ intersected_rule))
+ num_rules++;
+ memset(intersected_rule, 0,
+ sizeof(struct ieee80211_reg_rule));
+ }
+ }
+
+ if (!num_rules)
+ return NULL;
+
+ size_of_regd = sizeof(struct ieee80211_regdomain) +
+ ((num_rules + 1) * sizeof(struct ieee80211_reg_rule));
+
+ rd = kzalloc(size_of_regd, GFP_KERNEL);
+ if (!rd)
+ return NULL;
+
+ for (x = 0; x < rd1->n_reg_rules; x++) {
+ rule1 = &rd1->reg_rules[x];
+ for (y = 0; y < rd2->n_reg_rules; y++) {
+ rule2 = &rd2->reg_rules[y];
+ /* This time around instead of using the stack lets
+ * write to the target rule directly saving ourselves
+ * a memcpy() */
+ intersected_rule = &rd->reg_rules[rule_idx];
+ r = reg_rules_intersect(rule1, rule2,
+ intersected_rule);
+ /* No need to memset here the intersected rule here as
+ * we're not using the stack anymore */
+ if (r)
+ continue;
+ rule_idx++;
+ }
+ }
+
+ if (rule_idx != num_rules) {
+ kfree(rd);
+ return NULL;
+ }
+
+ rd->n_reg_rules = num_rules;
+ rd->alpha2[0] = '9';
+ rd->alpha2[1] = '8';
+
+ return rd;
+}
+