Add possibility to unsubscribe from events

Add possibility to unsubscribe from events using 'unsubscribe' verb
with the same json payload used for subscribe.

BUG-AGL: SPEC-2833

Change-Id: Ie01f36b2bf0a446cc80b09d79417a301ce9ecfff
Signed-off-by: Jonathan Aillet <jonathan.aillet@iot.bzh>

3 files changed, 70 insertions, 27 deletions

diff --git a/alsa-binding/Alsa-ApiHat.c b/alsa-binding/Alsa-ApiHat.c
index 470467b..5575a9a 100644
--- a/alsa-binding/Alsa-ApiHat.c
+++ b/alsa-binding/Alsa-ApiHat.c
@@ -44,7 +44,8 @@ static const afb_verb_t api_verbs[] = {
     { .verb = "infoget", .callback = alsaGetInfo, .info="Return sound cards list"},
     { .verb = "ctlget", .callback = alsaGetCtls, .info="Get one or many control values"},
     { .verb = "ctlset", .callback = alsaSetCtls, .info="Set one control or more"},
-    { .verb = "subscribe", .callback = alsaEvtSubcribe, .info="subscribe to alsa events"},
+    { .verb = "subscribe", .callback = alsaEvtSubscribe, .info="subscribe to alsa events"},
+    { .verb = "unsubscribe", .callback = alsaEvtUnsubscribe, .info="unsubscribe to alsa events"},
     { .verb = "cardidget", .callback = alsaGetCardId, .info="get sound card id"},
     { .verb = "halregister", .callback = alsaRegisterHal, .info="register a new HAL in alsacore"},
     { .verb = "hallist", .callback = alsaActiveHal, .info="Get list of currently active HAL"},
diff --git a/alsa-binding/Alsa-ApiHat.h b/alsa-binding/Alsa-ApiHat.h
index 209c65b..21aaa61 100644
--- a/alsa-binding/Alsa-ApiHat.h
+++ b/alsa-binding/Alsa-ApiHat.h
@@ -44,10 +44,10 @@
 #define NO_SUBDEVICE_SELECTED   -1
 
 typedef enum {
-  QUERY_QUIET   =0,
-  QUERY_COMPACT =1,
-  QUERY_VERBOSE =2,
-  QUERY_FULL    =3,
+    QUERY_QUIET   = 0,
+    QUERY_COMPACT = 1,
+    QUERY_VERBOSE = 2,
+    QUERY_FULL    = 3,
 } queryModeE;
 
 typedef enum {
@@ -60,6 +60,11 @@ typedef enum {
     CONTROL_REMOVE
 } ControlAddRemoveT;
 
+typedef enum {
+    EVENT_SUBSCRIBE,
+    EVENT_UNSUBSCRIBE
+} EventSubscribeUnsubscribeT;
+
 // structure to store card
 typedef struct {
     int cardNb;
@@ -77,8 +82,8 @@ typedef struct {
 
 // generic structure to pass parsed query values
 typedef struct {
-  json_object *numidsJ;
-  int count;
+    json_object *numidsJ;
+    int count;
 } controlQueryValuesT;
 
 // use to store crl numid user request
@@ -114,7 +119,8 @@ PUBLIC void alsaAddCustomCtls(afb_req_t request);
 PUBLIC void alsaRemoveCustomCtls(afb_req_t request);
 
 // AlsaRegEvt
-PUBLIC void alsaEvtSubcribe (afb_req_t request);
+PUBLIC void alsaEvtSubscribe (afb_req_t request);
+PUBLIC void alsaEvtUnsubscribe (afb_req_t request);
 PUBLIC void alsaGetCardId (afb_req_t request);
 PUBLIC void alsaRegisterHal (afb_req_t request);
 PUBLIC void alsaActiveHal (afb_req_t request);
diff --git a/alsa-binding/Alsa-RegEvt.c b/alsa-binding/Alsa-RegEvt.c
index a60ffc8..a9cce2b 100644
--- a/alsa-binding/Alsa-RegEvt.c
+++ b/alsa-binding/Alsa-RegEvt.c
@@ -192,7 +192,7 @@ STATIC void freeCardAlsaControlHandle(ctrlEvtHandleT **cardControlHandle)
 
 STATIC void updateSelectedAlsaCardsAvailabilityAndFireEvents(sndCardsT *sndCards, int first, int last)
 {
-    int idx, available;
+    int idx, available, subscriberCount = -1;
     char *cardId;
 
     json_object *generatedEventJ = NULL;
@@ -213,7 +213,7 @@ STATIC void updateSelectedAlsaCardsAvailabilityAndFireEvents(sndCardsT *sndCards
 
             if(sndCards->cardMonitoring &&
                ! wrap_json_pack(&generatedEventJ, "{s:o}", "cardAdded", getCardInfo(idx)))
-                afb_event_push(sndCards->cardMonitoring->afbevt, generatedEventJ);
+                subscriberCount = afb_event_push(sndCards->cardMonitoring->afbevt, generatedEventJ);
         }
         else if(! available && sndCards->sndHandles[idx].available) {
             sndCards->sndHandles[idx].available = 0;
@@ -221,7 +221,7 @@ STATIC void updateSelectedAlsaCardsAvailabilityAndFireEvents(sndCardsT *sndCards
             if(sndCards->cardMonitoring &&
                (asprintf(&cardId, "hw:%i", idx) > 0) &&
                ! wrap_json_pack(&generatedEventJ, "{s:s}", "cardRemoved", cardId))
-                afb_event_push(sndCards->cardMonitoring->afbevt, generatedEventJ);
+                subscriberCount = afb_event_push(sndCards->cardMonitoring->afbevt, generatedEventJ);
 
             if(sndCards->sndHandles[idx].evtHandle) {
                 sd_event_source_unref(sndCards->sndHandles[idx].evtHandle->src);
@@ -232,6 +232,11 @@ STATIC void updateSelectedAlsaCardsAvailabilityAndFireEvents(sndCardsT *sndCards
             }
         }
     }
+
+    if(! subscriberCount) {
+        AFB_WARNING("Nobody listening for 'card-monitoring' events, stop monitoring from now on");
+        freeSndCardHandle(&sndCards->cardMonitoring);
+    }
 }
 
 STATIC void updateAllAlsaCardsAvailabilityAndFireEvents(sndCardsT *sndCards) {
@@ -326,7 +331,7 @@ STATIC int sndCardEventCB(sd_event_source* src, int fd, uint32_t revents, void*
 // This routine is called when ALSA control events are fired
 STATIC int sndCtlEventCB(sd_event_source* src, int fd, uint32_t revents, void* userData)
 {
-    int err, ctlNumid;
+    int err, ctlNumid, subscriberCount = -1;
     unsigned int mask;
 
     snd_ctl_elem_id_t *elemId;
@@ -398,21 +403,29 @@ STATIC int sndCtlEventCB(sd_event_source* src, int fd, uint32_t revents, void* u
             wrap_json_object_add(ctlEventJ, ctlEventAdditionalInfoJ);
 
         AFB_DEBUG("sndCtlEventCB=%s", json_object_get_string(ctlEventJ));
+        subscriberCount = afb_event_push(sndHandle->evtHandle->afbevt, ctlEventJ);
+    }
 
-        afb_event_push(sndHandle->evtHandle->afbevt, ctlEventJ);
+    if(! subscriberCount) {
+        AFB_WARNING("Nobody listening for card %i control events, stop monitoring from now on", snd_ctl_event_elem_get_interface(eventId));
+        freeCardAlsaControlHandle(&sndHandle->evtHandle);
+        return -4;
     }
 
     return 0;
 }
 
 // Subscribe to each time a sound card is added/removed (using inotify '/dev/snd/by-path' events)
-STATIC afb_event_t alsaEvtSubscribeSoundCardEvent(afb_req_t request,
-                                                  sndCardsT *sndCards)
+STATIC afb_event_t alsaEvtSubscribeUnsubscribeSoundCardEvent(afb_req_t request,
+                                                             sndCardsT *sndCards,
+                                                             EventSubscribeUnsubscribeT subscriptionType)
 {
     int err;
 
     if(sndCards->cardMonitoring)
         return sndCards->cardMonitoring->afbevt;
+    else if(subscriptionType == EVENT_UNSUBSCRIBE)
+        return NULL;
 
     updateAllAlsaCardsAvailabilityAndFireEvents(sndCards);
 
@@ -467,9 +480,10 @@ STATIC afb_event_t alsaEvtSubscribeSoundCardEvent(afb_req_t request,
 }
 
 // Subscribe to every Alsa CtlEvent send by a given board
-STATIC afb_event_t alsaEvtSubscribeAlsaControlEvent(afb_req_t request,
-                                                    sndCardsT *sndCards,
-                                                    char* devId)
+STATIC afb_event_t alsaEvtSubscribeUnsubscribeAlsaControlEvent(afb_req_t request,
+                                                               sndCardsT *sndCards,
+                                                               char* devId,
+                                                               EventSubscribeUnsubscribeT subscriptionType)
 {
     sndHandleT *currentSndHandle = NULL;
     snd_ctl_t *ctlDev = NULL;
@@ -505,6 +519,10 @@ STATIC afb_event_t alsaEvtSubscribeAlsaControlEvent(afb_req_t request,
         snd_ctl_close(ctlDev);
         return currentSndHandle->evtHandle->afbevt;
     }
+    else if(subscriptionType == EVENT_UNSUBSCRIBE) {
+        snd_ctl_close(ctlDev);
+        return NULL;
+    }
 
     currentSndHandle->evtHandle = malloc(sizeof (ctrlEvtHandleT));
     currentSndHandle->evtHandle->ctlDev = ctlDev;
@@ -545,8 +563,9 @@ STATIC afb_event_t alsaEvtSubscribeAlsaControlEvent(afb_req_t request,
 }
 
 // Subscribe to alsacore event
-PUBLIC void alsaEvtSubcribe(afb_req_t request) {
-    int err;
+PUBLIC void alsaEvtSubscribeUnsubscribe(afb_req_t request, EventSubscribeUnsubscribeT subscriptionType)
+{
+    int err = -1;
 
     EventTypeT eventType;
 
@@ -554,7 +573,7 @@ PUBLIC void alsaEvtSubcribe(afb_req_t request) {
 
     static sndCardsT *sndCards = NULL;
 
-    afb_event_t eventToSubscribe;
+    afb_event_t eventToSubscribeUnsubscribe;
 
     json_object *queryJ;
 
@@ -574,11 +593,11 @@ PUBLIC void alsaEvtSubcribe(afb_req_t request) {
                     return;
                 }
 
-                eventToSubscribe = alsaEvtSubscribeAlsaControlEvent(request, sndCards, devId);
+                eventToSubscribeUnsubscribe = alsaEvtSubscribeUnsubscribeAlsaControlEvent(request, sndCards, devId, subscriptionType);
                 break;
 
             case CARD_MONITORING_EVENTS:
-                eventToSubscribe = alsaEvtSubscribeSoundCardEvent(request, sndCards);
+                eventToSubscribeUnsubscribe = alsaEvtSubscribeUnsubscribeSoundCardEvent(request, sndCards, subscriptionType);
                 break;
 
             case UNKNOWN_EVENT:
@@ -587,19 +606,36 @@ PUBLIC void alsaEvtSubcribe(afb_req_t request) {
                 return;
     }
 
-    if(! eventToSubscribe)
+    if(! eventToSubscribeUnsubscribe)
         return;
 
-    // subscribe to binder event
-    err = afb_req_subscribe(request, eventToSubscribe);
+    // subscribe/unsubscribe to binder event
+    if(subscriptionType == EVENT_SUBSCRIBE)
+        err = afb_req_subscribe(request, eventToSubscribeUnsubscribe);
+    else if(subscriptionType == EVENT_UNSUBSCRIBE)
+        err = afb_req_unsubscribe(request, eventToSubscribeUnsubscribe);
+
     if(err) {
-        afb_req_fail_f(request, "register-eventname", "Cannot subscribe binder event");
+        afb_req_fail_f(request,
+                       "register-eventname",
+                       "Cannot %s binder event",
+                       (subscriptionType == EVENT_SUBSCRIBE) ? "subscribe" : "unsubscribe");
         return;
     }
 
     afb_req_success(request, NULL, NULL);
 }
 
+PUBLIC void alsaEvtSubscribe(afb_req_t request)
+{
+    alsaEvtSubscribeUnsubscribe(request, EVENT_SUBSCRIBE);
+}
+
+PUBLIC void alsaEvtUnsubscribe(afb_req_t request)
+{
+    alsaEvtSubscribeUnsubscribe(request, EVENT_UNSUBSCRIBE);
+}
+
 // Subscribe to every Alsa CtlEvent send by a given board
 
 STATIC json_object *alsaProbeCardId(afb_req_t request) {