Add events when PCM availability changes

Add PCM availability application framework events to be notified
when ALSA PCM availability changes.

Use subscribe verb and json
'{ "event" : "pcm", "name" : "hw:3,2,1", "stream" : 0 }'
to subscribe to playback PCM 'hw:3,2,1' availability events.
Use subscribe verb and json
'{ "event" : "pcm", "name" : "hw:1,2,3", "stream" : 1 }''
to subscribe to capture PCM 'hw:1,2,3' availability events.
from removed card events.

To handle PCM events, inode notification (using inotify) is used
on '/dev/snd/pcm*' file (e.g. '/dev/snd/pcmC0D0p')
to monitor PCM availability.

BUG-AGL: SPEC-2835

Change-Id: I5bfaef73b896fa7213e1308035eeaff1464f62f6
Signed-off-by: Jonathan Aillet <jonathan.aillet@iot.bzh>

2 files changed, 347 insertions, 1 deletions

diff --git a/alsa-binding/Alsa-RegEvt.c b/alsa-binding/Alsa-RegEvt.c
index a9cce2b..1a803cb 100644
--- a/alsa-binding/Alsa-RegEvt.c
+++ b/alsa-binding/Alsa-RegEvt.c
@@ -20,6 +20,8 @@
 
 #include <sys/inotify.h>
 
+#include <urcu/list.h>
+
 #include <afb-timer.h>
 
 #include <wrap-json.h>
@@ -32,6 +34,9 @@
 
 #define CARD_DIR_TO_WATCH       "/dev/snd/by-path"
 
+#define PCM_DEV_FILE_STRING     "/dev/snd/pcmC%iD%i%c"
+#define PCM_EVENT_NAME          "pcm-%s-%i,%i,%i-monitoring"
+
 #ifndef MAX_SND_HAL
 #define MAX_SND_HAL 10
 #endif
@@ -39,10 +44,28 @@
 typedef enum {
     UNKNOWN_EVENT = 0,
     CARD_CONTROL_CHANGE_EVENTS = 1,
-    CARD_MONITORING_EVENTS = 2
+    CARD_MONITORING_EVENTS = 2,
+    PCM_AVAILABILITY_EVENTS = 3
 } EventTypeT;
 
 typedef struct {
+    unsigned int card;
+    unsigned int device;
+    unsigned int subdevice;
+    snd_pcm_stream_t stream;
+    int available;
+
+    char *pcmFileToMonitor;
+    int fd;
+    int wd;
+
+    sd_event_source *src;
+    afb_event_t afbevt;
+
+    struct cds_list_head node;
+} pcmEvtHandleT;
+
+typedef struct {
     int fd;
     int wd;
     sd_event_source *src;
@@ -65,6 +88,7 @@ typedef struct {
 typedef struct {
     sndHandleT sndHandles[MAX_SND_CARD];
     sndCardEvtHandleT *cardMonitoring;
+    struct cds_list_head pcmMonitoringHead;
     afb_api_t apiHandle;
 } sndCardsT;
 
@@ -105,6 +129,9 @@ STATIC EventTypeT alsaGetDevIdFromString(char *eventTypeString)
     if(! strcasecmp(eventTypeString, "cards"))
         return CARD_MONITORING_EVENTS;
 
+    if(! strcasecmp(eventTypeString, "pcm"))
+        return PCM_AVAILABILITY_EVENTS;
+
     return UNKNOWN_EVENT;
 }
 
@@ -141,6 +168,31 @@ PUBLIC queryModeE alsaGetModeFromQuery(json_object *queryJ)
    return mode;
 }
 
+STATIC void freePcmHandle(pcmEvtHandleT *pcmEventHandle)
+{
+    if(! pcmEventHandle)
+        return;
+
+    if(pcmEventHandle->node.prev && pcmEventHandle->node.next)
+        cds_list_del(&pcmEventHandle->node);
+
+    if(pcmEventHandle->src)
+        sd_event_source_unref(pcmEventHandle->src);
+
+    if(afb_event_is_valid(pcmEventHandle->afbevt))
+        afb_event_unref(pcmEventHandle->afbevt);
+
+    if(pcmEventHandle->fd != -1 && pcmEventHandle->wd != -1)
+        inotify_rm_watch(pcmEventHandle->fd, pcmEventHandle->wd);
+
+    if(pcmEventHandle->fd != -1)
+        close(pcmEventHandle->fd);
+
+    free(pcmEventHandle->pcmFileToMonitor);
+
+    free(pcmEventHandle);
+}
+
 STATIC void freeSndCardHandle(sndCardEvtHandleT **cardMonitoringHandle)
 {
     sndCardEvtHandleT *cardMonitoringHandleToFree;
@@ -268,6 +320,99 @@ STATIC int sndCardTimerForCreatedFileCB(TimerHandleT *context)
     return 1;
 }
 
+STATIC int pcmEventCB(sd_event_source* src, int fd, uint32_t revents, void* userData)
+{
+    int err, pcmStatus, subscriberCount = -1;
+    ssize_t length, i = 0;
+    char buffer[INOTIFY_EVENT_BUF_LEN], *pcmName;
+
+    struct inotify_event *event;
+
+    pcmEvtHandleT *pcmEventHandle = (pcmEvtHandleT *) userData;
+
+    json_object *eventJ = NULL;
+
+    if(revents & EPOLLERR) {
+        AFB_ERROR("An error has been send by event loop polling, prevent new errors to be fired by deleting event src");
+        freePcmHandle(pcmEventHandle);
+        return -1;
+    }
+
+    if(revents & EPOLLIN) {
+        length = read(fd, buffer, INOTIFY_EVENT_BUF_LEN);
+        if(length < 0) {
+            AFB_ERROR("Nothing read using inotify");
+            freePcmHandle(pcmEventHandle);
+            return -2;
+        }
+
+        while(i < length) {
+            event = (struct inotify_event *) &buffer[i];
+
+            i += INOTIFY_EVENT_SIZE + event->len;
+
+            if((event->mask & IN_DELETE) || (event->mask & IN_DELETE_SELF)) {
+                AFB_WARNING("Monitored file has been deleted, delete monitoring");
+                freePcmHandle(pcmEventHandle);
+                return -3;
+            }
+
+            if((event->mask & IN_OPEN) || (event->mask & IN_CLOSE)) {
+                pcmStatus = alsaIsPcmAvailableUsingId(pcmEventHandle->card,
+                                                      pcmEventHandle->device,
+                                                      pcmEventHandle->subdevice,
+                                                      pcmEventHandle->stream);
+                if(pcmEventHandle->available != pcmStatus) {
+                    pcmEventHandle->available = pcmStatus;
+
+                    err = asprintf(&pcmName,
+                                   "hw:%i,%i,%i",
+                                   pcmEventHandle->card,
+                                   pcmEventHandle->device,
+                                   pcmEventHandle->subdevice);
+                    if(err <= 0) {
+                        AFB_ERROR("Did not succeed to generate pcm name string (card : %i, device : %i, subdevice : %i)",
+                                  pcmEventHandle->card,
+                                  pcmEventHandle->device,
+                                  pcmEventHandle->subdevice);
+                        freePcmHandle(pcmEventHandle);
+                        return -4;
+                    }
+
+                    err = wrap_json_pack(&eventJ,
+                                         "{s:s, s:i, s:i}",
+                                         "name", pcmName,
+                                         "stream", pcmEventHandle->stream,
+                                         "available", pcmEventHandle->available);
+                    if(err) {
+                        AFB_ERROR("Did not succeed to generate pcm event json info (name : %s, stream : %s, available : %i)",
+                                  pcmName,
+                                  (pcmEventHandle->stream == SND_PCM_STREAM_PLAYBACK) ? "playback" : "capture",
+                                  pcmEventHandle->available);
+                        free(pcmName);
+                        freePcmHandle(pcmEventHandle);
+                        return -5;
+                    }
+
+                    subscriberCount = afb_event_push(pcmEventHandle->afbevt, eventJ);
+                }
+            }
+        }
+    }
+
+    if(! subscriberCount) {
+        AFB_WARNING("Nobody listening for pcm %s hw:%i,%i,%i availability events, stop monitoring from now on",
+                    (pcmEventHandle->stream == SND_PCM_STREAM_PLAYBACK) ? "playback" : "capture",
+                    pcmEventHandle->card,
+                    pcmEventHandle->device,
+                    pcmEventHandle->subdevice);
+        freePcmHandle(pcmEventHandle);
+        return -6;
+    }
+
+    return 0;
+}
+
 // This routine is called when sound cards are added/removed (when inotify '/dev/snd/by-path' events are fired)
 STATIC int sndCardEventCB(sd_event_source* src, int fd, uint32_t revents, void* userData)
 {
@@ -415,6 +560,201 @@ STATIC int sndCtlEventCB(sd_event_source* src, int fd, uint32_t revents, void* u
     return 0;
 }
 
+STATIC afb_event_t alsaEvtSubscribeUnsubscribePcmAvailabilityEvent(afb_req_t request,
+                                                                   json_object *queryJ,
+                                                                   sndCardsT *sndCards,
+                                                                   EventSubscribeUnsubscribeT subscriptionType)
+{
+    int err,
+        card = NO_CARD_SELECTED,
+        device = NO_DEVICE_SELECTED,
+        subdevice = NO_SUBDEVICE_SELECTED;
+
+    char *pcmName = NULL, *pcmEventName = NULL;
+
+    snd_pcm_stream_t stream;
+
+    pcmEvtHandleT *requestedPcmEventHandle = NULL, *currentPcmEventHandle;
+
+    if(! request || ! queryJ || ! sndCards) {
+        afb_req_fail(request, "invalid-args", "Arguments of call are invalid");
+        return NULL;
+    }
+
+    err = wrap_json_unpack(queryJ,
+                           "{s:s, s?:i, s?:i, s?:i, s?:s, s:i !}",
+                           "event", NULL,
+                           "card", &card,
+                           "device", &device,
+                           "subdevice", &subdevice,
+                           "name", &pcmName,
+                           "stream", &stream);
+    if(err || (! pcmName && (card == NO_CARD_SELECTED || device == NO_DEVICE_SELECTED || subdevice == NO_SUBDEVICE_SELECTED))) {
+        afb_req_fail_f(request, "invalid_request", "Request json is invalid (%s)", json_object_get_string(queryJ));
+        return NULL;
+    }
+
+    if(pcmName && (sscanf(pcmName, "hw:%i,%i,%i", &card, &device, &subdevice) != 3)) {
+        afb_req_fail_f(request, "invalid_request", "Request pcm name is invalid (%s)", pcmName);
+        return NULL;
+    }
+
+    if(card < 0 || card > MAX_SND_CARD ||
+       device < 0 || device > MAX_CARD_DEVICES ||
+       subdevice < 0 || subdevice > MAX_DEVICE_SUBDEVICES) {
+        afb_req_fail_f(request,
+                       "invalid_request",
+                       "Requested pcm is not valid (card : %i, device : %i, subdevice : %i)",
+                       card,
+                       device,
+                       subdevice);
+        return NULL;
+    }
+
+    cds_list_for_each_entry(currentPcmEventHandle, &sndCards->pcmMonitoringHead, node) {
+        if(currentPcmEventHandle->card == card &&
+           currentPcmEventHandle->device == device &&
+           currentPcmEventHandle->subdevice == subdevice &&
+           currentPcmEventHandle->stream == stream) {
+            requestedPcmEventHandle = currentPcmEventHandle;
+            break;
+        }
+    }
+
+    if(requestedPcmEventHandle) {
+        return requestedPcmEventHandle->afbevt;
+    }
+    else if(subscriptionType == EVENT_UNSUBSCRIBE) {
+        afb_req_fail_f(request,
+                       "unknown_event",
+                       "Can not unsubscribe unknown event (card : %i, device : %i, subdevice : %i, stream : %i)",
+                       card,
+                       device,
+                       subdevice,
+                       stream);
+        return NULL;
+    }
+
+    requestedPcmEventHandle = calloc(1, sizeof(pcmEvtHandleT));
+    if(! requestedPcmEventHandle) {
+        afb_req_fail_f(request,
+                       "eventhandle_alloc",
+                       "Error when tried to allocate pcm event data structure (card : %i, device : %i, stream : %i, stream : %i)",
+                       card,
+                       device,
+                       subdevice,
+                       stream);
+       return NULL;;
+    }
+
+    requestedPcmEventHandle->card = card;
+    requestedPcmEventHandle->device = device;
+    requestedPcmEventHandle->subdevice = subdevice;
+    requestedPcmEventHandle->stream = stream;
+    requestedPcmEventHandle->fd = -1;
+    requestedPcmEventHandle->wd = -1;
+
+    err = asprintf(&requestedPcmEventHandle->pcmFileToMonitor,
+                   PCM_DEV_FILE_STRING,
+                   card,
+                   device,
+                   (stream == SND_PCM_STREAM_PLAYBACK) ? 'p' : 'c');
+    if(err <= 0) {
+        afb_req_fail_f(request,
+                       "monitored_file",
+                       "Did not succeed to generate pcm file to monitor string (card : %i, device : %i, stream : %i)",
+                       card,
+                       device,
+                       stream);
+        freePcmHandle(requestedPcmEventHandle);
+        return NULL;
+    }
+
+    err = asprintf(&pcmEventName,
+                   PCM_EVENT_NAME,
+                   (stream == SND_PCM_STREAM_PLAYBACK) ? "playback" : "capture",
+                   card,
+                   device,
+                   subdevice);
+    if(err <= 0) {
+        afb_req_fail_f(request,
+                       "pcm_event_name",
+                       "Did not succeed to generate pcm event name string (card : %i, device : %i, stream : %i, stream : %i)",
+                       card,
+                       device,
+                       subdevice,
+                       stream);
+        freePcmHandle(requestedPcmEventHandle);
+        return NULL;
+    }
+
+    requestedPcmEventHandle->afbevt = afb_daemon_make_event(pcmEventName);
+    if(! afb_event_is_valid(requestedPcmEventHandle->afbevt)) {
+        afb_req_fail_f(request, "pcm-monitoring-event", "Cannot register new %s event", pcmEventName);
+        free(pcmEventName);
+        freePcmHandle(requestedPcmEventHandle);
+        return NULL;
+    }
+
+    free(pcmEventName);
+
+    requestedPcmEventHandle->fd = inotify_init();
+    if(requestedPcmEventHandle->fd < 0) {
+        afb_req_fail_f(request, "inotify-init", "Error %s happened while getting file descriptor for inotify", strerror(errno));
+        freePcmHandle(requestedPcmEventHandle);
+        return NULL;
+    }
+
+    requestedPcmEventHandle->wd = inotify_add_watch(requestedPcmEventHandle->fd,
+                                                    requestedPcmEventHandle->pcmFileToMonitor,
+                                                    IN_ALL_EVENTS);
+    if(requestedPcmEventHandle->wd < 0) {
+        afb_req_fail_f(request,
+                       "inotify-watch",
+                       "Error %s happened while setting watcher on '%s' file using inotify",
+                       strerror(errno),
+                       requestedPcmEventHandle->pcmFileToMonitor);
+        freePcmHandle(requestedPcmEventHandle);
+        return NULL;
+    }
+
+    requestedPcmEventHandle->available = alsaIsPcmAvailableUsingId(card, device, subdevice, stream);
+    if(requestedPcmEventHandle->available < 0) {
+        afb_req_fail_f(request,
+                       "pcm-availability",
+                       "Did not succeed to get pcm current availability (card : %i, device : %i, stream : %i, stream : %i)",
+                       card,
+                       device,
+                       subdevice,
+                       stream);
+        freePcmHandle(requestedPcmEventHandle);
+        return NULL;
+    }
+
+    err = sd_event_add_io(afb_daemon_get_event_loop(),
+                          &requestedPcmEventHandle->src,
+                          requestedPcmEventHandle->fd,
+                          EPOLLIN,
+                          pcmEventCB,
+                          requestedPcmEventHandle);
+    if(err < 0) {
+        afb_req_fail_f(request,
+                       "register-mainloop",
+                       "Cannot hook pcm %s hw:%i,%i,%i event to mainloop err=%d",
+                       (stream == SND_PCM_STREAM_PLAYBACK) ? "playback" : "capture",
+                       card,
+                       device,
+                       subdevice,
+                       err);
+        freePcmHandle(requestedPcmEventHandle);
+        return NULL;
+    }
+
+    cds_list_add_tail(&requestedPcmEventHandle->node, &sndCards->pcmMonitoringHead);
+
+    return requestedPcmEventHandle->afbevt;
+}
+
 // Subscribe to each time a sound card is added/removed (using inotify '/dev/snd/by-path' events)
 STATIC afb_event_t alsaEvtSubscribeUnsubscribeSoundCardEvent(afb_req_t request,
                                                              sndCardsT *sndCards,
@@ -580,6 +920,7 @@ PUBLIC void alsaEvtSubscribeUnsubscribe(afb_req_t request, EventSubscribeUnsubsc
     if(! sndCards) {
         sndCards = calloc(1, sizeof(sndCardsT));
         sndCards->apiHandle = afb_req_get_api(request);
+        CDS_INIT_LIST_HEAD(&sndCards->pcmMonitoringHead);
     }
 
     queryJ = afb_req_json(request);
@@ -600,6 +941,10 @@ PUBLIC void alsaEvtSubscribeUnsubscribe(afb_req_t request, EventSubscribeUnsubsc
                 eventToSubscribeUnsubscribe = alsaEvtSubscribeUnsubscribeSoundCardEvent(request, sndCards, subscriptionType);
                 break;
 
+            case PCM_AVAILABILITY_EVENTS:
+                eventToSubscribeUnsubscribe = alsaEvtSubscribeUnsubscribePcmAvailabilityEvent(request, queryJ, sndCards, subscriptionType);
+                break;
+
             case UNKNOWN_EVENT:
             default:
                 afb_req_fail_f(request, "unknown-event", "Invalid query='%s'", json_object_get_string(queryJ));
diff --git a/conf.d/cmake/config.cmake b/conf.d/cmake/config.cmake
index 27b0dfd..55dd171 100644
--- a/conf.d/cmake/config.cmake
+++ b/conf.d/cmake/config.cmake
@@ -75,6 +75,7 @@ set (PKG_REQUIRED_LIST
 	libmicrohttpd>=0.9.55
 	libafbwsc
 	alsa>=1.1.2
+	liburcu
 	afb-helpers
 )