PTP: drop the "Preferred TimeTransmitter" role

It behaved exactly like auto (clock class 248); the only difference was a
priority1 suggestion in the page. Roles are now slave|auto; to prefer this
device, use auto with a low priority1. A stored "master" is converted to
auto at boot (new cfg_set_string, like cfg_set_number).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

components/aes67_ptp/aes67_ptp.c

@@ -1,7 +1,10 @@
 #include "aes67_ptp.h"
 
+#include <string.h>
+
 #include "aes67_cfg.h"
 #include "aes67_web.h"
+#include "esp_log.h"
 #include "ptp_clock.h"
 #include "ptp_hw.h"
 
@@ -14,7 +17,7 @@ static const char PTP_DEFAULTS[] =
 static bool ptp_validate(const cJSON *g, char *err, size_t n)
 {
     static const char *const modes[] = { "multicast", "hybrid", NULL };
-    static const char *const roles[] = { "slave", "auto", "master", NULL };
+    static const char *const roles[] = { "slave", "auto", NULL };
     return cfg_check_enum(g, "mode", modes, err, n) &&
            cfg_check_enum(g, "role", roles, err, n) &&
            cfg_check_int(g, "domain", 0, 127, err, n) &&
@@ -34,7 +37,20 @@ static void ptp_apply(const cJSON *g)
 
 esp_err_t aes67_ptp_init(void)
 {
-    return cfg_register("ptp", PTP_DEFAULTS, ptp_validate, ptp_apply);
+    esp_err_t err = cfg_register("ptp", PTP_DEFAULTS, ptp_validate, ptp_apply);
+    if (err != ESP_OK) {
+        return err;
+    }
+    // Role "master" was dropped (it behaved like auto; a low priority1 does the same). Stored values
+    // aren't re-validated, so convert it here.
+    cJSON *c = cfg_get("ptp");
+    bool master = !strcmp(cJSON_GetObjectItemCaseSensitive(c, "role")->valuestring, "master");
+    cJSON_Delete(c);
+    if (master) {
+        ESP_LOGW("ptp", "stored role \"master\" is no longer offered: now \"auto\" (same behaviour)");
+        cfg_set_string("ptp", "role", "auto", false);
+    }
+    return ESP_OK;
 }
 
 esp_err_t aes67_ptp_start(esp_eth_handle_t eth)

components/aes67_ptp/ptp_clock.c

@@ -622,8 +622,8 @@ static void load_config(void)
     s.cfg_log_sync = cJSON_GetObjectItem(c, "log_sync")->valueint;
     s.cfg_log_announce = cJSON_GetObjectItem(c, "log_announce")->valueint;
     s.cfg_log_dreq = cJSON_GetObjectItem(c, "log_delay_req")->valueint;
-    // Roles (docs): slave = clockClass 255, never transmits; auto/master = 248 with the configured
-    // priorities (auto 250/250 by default, master e.g. p1 100).
+    // Roles (docs): slave = clockClass 255, never transmits; auto = 248 with the configured priorities
+    // (250/250 by default: loses to any real GM; a lower priority1 prefers this device).
     s.slave_only = strcmp(cJSON_GetObjectItem(c, "role")->valuestring, "slave") == 0;
     s.hybrid = strcmp(cJSON_GetObjectItem(c, "mode")->valuestring, "hybrid") == 0;
     s.own_class = s.slave_only ? 255 : 248;
@@ -711,7 +711,7 @@ static void ptp_task(void *arg)
             int tos2 = s.dscp << 2;
             setsockopt(s.gen, IPPROTO_IP, IP_TOS, &tos2, sizeof(tos2));
             ESP_LOGI(TAG, "config applied: role %s, mode %s, p1 %u p2 %u, domain %u",
-                     s.slave_only ? "slave" : "auto/master", s.hybrid ? "hybrid" : "multicast",
+                     s.slave_only ? "slave" : "auto", s.hybrid ? "hybrid" : "multicast",
                      s.own.p1, s.own.p2, s.domain);
             // Re-run the decision: a foreign GM worse than our new dataset is dropped; as
             // TimeTransmitter with role slave we stop.

components/aes67_web/cfg.c

@@ -295,6 +295,37 @@ esp_err_t cfg_set_number(const char *group, const char *key, double value, bool
     return err;
 }
 
+esp_err_t cfg_set_string(const char *group, const char *key, const char *value, bool apply)
+{
+    if (!s_lock) {
+        return ESP_ERR_INVALID_STATE;
+    }
+    xSemaphoreTake(s_lock, portMAX_DELAY);
+    cfg_group_t *g = find(group);
+    cJSON *cur = g ? cJSON_GetObjectItemCaseSensitive(g->values, key) : NULL;
+    esp_err_t err = ESP_OK;
+    if (!cur || !cJSON_IsString(cur)) {
+        err = ESP_ERR_NOT_FOUND;
+    } else {
+        cJSON_ReplaceItemInObjectCaseSensitive(g->values, key, cJSON_CreateString(value));
+        nvs_handle_t h;
+        if (s_nvs_ok && (err = nvs_open(NVS_NAMESPACE, NVS_READWRITE, &h)) == ESP_OK) {
+            err = store(h, g);
+            if (err == ESP_OK) {
+                err = nvs_commit(h);
+            }
+            nvs_close(h);
+        }
+    }
+    cJSON *copy = err == ESP_OK && apply && g->apply ? cJSON_Duplicate(g->values, true) : NULL;
+    xSemaphoreGive(s_lock);
+    if (copy) {
+        g->apply(copy);
+        cJSON_Delete(copy);
+    }
+    return err;
+}
+
 /* ----- HTTP ----- */
 
 static esp_err_t config_get(httpd_req_t *req)

components/aes67_web/include/aes67_cfg.h

@@ -26,6 +26,8 @@ cJSON *cfg_get(const char *group);
 // Firmware-side change of one number (e.g. aes67.session_ver): stored like a POST, no validation.
 // apply = false skips the group's apply callback (e.g. to avoid restarting the stream).
 esp_err_t cfg_set_number(const char *group, const char *key, double value, bool apply);
+// Same for a string value.
+esp_err_t cfg_set_string(const char *group, const char *key, const char *value, bool apply);
 
 // Validation helpers for validate callbacks. Each returns false and fills err on failure.
 bool cfg_check_num(const cJSON *g, const char *key, double min, double max, char *err, size_t n);