From 96f35e15a0980aa3df1d9ac3f7f8345c0464f18a Mon Sep 17 00:00:00 2001
From: Emil Svendsen <emilabildgaardsvendsen@gmail.com>
Date: Sun, 3 Mar 2024 10:01:59 +0100
Subject: [PATCH] alsa-pcm: bind_ctl: add better ctl name matching

For matching kctl without the numid you need to specify interface,
device, subdevice, name and index. So the current implementation can
only match kctls on IFACE_PCM, device 0, subdevice 0 and index 0.

Instead of adding all these matching parameters this commit fetches all
kctls attached to the audio card and match on the first occurred kctl
with matching name.

This should be sufficient for audio cards with unique kctl names. When
non unique names are needed, more kctl matching parameters needs to be
added.
---
 spa/plugins/alsa/alsa-pcm.c | 106 +++++++++++++++++++++++++++---------
 1 file changed, 80 insertions(+), 26 deletions(-)

diff --git a/spa/plugins/alsa/alsa-pcm.c b/spa/plugins/alsa/alsa-pcm.c
index 4fb1a1ad3..2263a39ff 100644
--- a/spa/plugins/alsa/alsa-pcm.c
+++ b/spa/plugins/alsa/alsa-pcm.c
@@ -693,6 +693,85 @@ static void bind_ctl_event(struct spa_source *source)
 	}
 }
 
+static void fetch_bind_ctls(struct state *state)
+{
+	snd_ctl_elem_list_t* element_list;
+	unsigned int elem_count = 0;
+	int err;
+
+	if (!state->num_bind_ctls)
+		return;
+
+	snd_ctl_elem_list_alloca(&element_list);
+
+	/* Get number of elements */
+	err = snd_ctl_elem_list(state->ctl, element_list);
+	if (SPA_UNLIKELY(err < 0)) {
+		spa_log_warn(state->log, "Couldn't get elem list count. Error: %s",
+			     snd_strerror(err));
+		return;
+	}
+
+	elem_count = snd_ctl_elem_list_get_count(element_list);
+	err = snd_ctl_elem_list_alloc_space(element_list, elem_count);
+	if (SPA_UNLIKELY(err < 0)) {
+		spa_log_error(state->log, "Couldn't allocate elem_list space. Error: %s",
+			      snd_strerror(err));
+		return;
+	}
+
+	/* Get identifiers */
+	err = snd_ctl_elem_list(state->ctl, element_list);
+	if (SPA_UNLIKELY(err < 0)) {
+		spa_log_warn(state->log, "Couldn't get elem list. Error: %s",
+			     snd_strerror(err));
+		goto cleanup;
+	}
+
+
+	for (unsigned int i = 0; i < state->num_bind_ctls; i++) {
+		unsigned int numid = 0;
+
+		for (unsigned int j = 0; i < elem_count; j++) {
+			const char* element_name = snd_ctl_elem_list_get_name(element_list, j);
+
+			if (!strcmp(element_name, state->bound_ctls[i].name)) {
+				numid = snd_ctl_elem_list_get_numid(element_list, j);
+				break;
+			}
+		}
+
+		/* zero = invalid numid */
+		if (SPA_UNLIKELY(!numid)) {
+			spa_log_warn(state->log, "Didn't find ctl: '%s', count: %u",
+				     state->bound_ctls[i].name, elem_count);
+			continue;
+		}
+
+		snd_ctl_elem_info_malloc(&state->bound_ctls[i].info);
+		snd_ctl_elem_info_set_numid(state->bound_ctls[i].info, numid);
+
+		err = snd_ctl_elem_info(state->ctl, state->bound_ctls[i].info);
+		if (SPA_UNLIKELY(err < 0)) {
+			spa_log_warn(state->log, "Could not read elem info for '%s': %s",
+				     state->bound_ctls[i].name, snd_strerror(err));
+
+			snd_ctl_elem_info_free(state->bound_ctls[i].info);
+			state->bound_ctls[i].info = NULL;
+			continue;
+		}
+
+		snd_ctl_elem_value_malloc(&state->bound_ctls[i].value);
+		snd_ctl_elem_value_set_numid(state->bound_ctls[i].value, numid);
+
+		spa_log_debug(state->log, "Binding ctl for '%s'",
+			      snd_ctl_elem_info_get_name(state->bound_ctls[i].info));
+	}
+
+cleanup:
+	snd_ctl_elem_list_free_space(element_list);
+}
+
 static void bind_ctls_for_params(struct state *state)
 {
 	struct pollfd pfds[16];
@@ -737,32 +816,7 @@ static void bind_ctls_for_params(struct state *state)
 		spa_loop_add_source(state->main_loop, &state->ctl_sources[i]);
 	}
 
-	for (unsigned int i = 0; i < state->num_bind_ctls; i++) {
-		snd_ctl_elem_id_t *id;
-
-		snd_ctl_elem_id_alloca(&id);
-		snd_ctl_elem_id_set_name(id, state->bound_ctls[i].name);
-		snd_ctl_elem_id_set_interface(id, SND_CTL_ELEM_IFACE_PCM);
-
-		snd_ctl_elem_info_malloc(&state->bound_ctls[i].info);
-		snd_ctl_elem_info_set_id(state->bound_ctls[i].info, id);
-
-		err = snd_ctl_elem_info(state->ctl, state->bound_ctls[i].info);
-		if (err < 0) {
-			spa_log_warn(state->log, "Could not read elem info for '%s': %s",
-					state->bound_ctls[i].name, snd_strerror(err));
-
-			snd_ctl_elem_info_free(state->bound_ctls[i].info);
-			state->bound_ctls[i].info = NULL;
-			continue;
-		}
-
-		snd_ctl_elem_value_malloc(&state->bound_ctls[i].value);
-		snd_ctl_elem_value_set_id(state->bound_ctls[i].value, id);
-
-		spa_log_debug(state->log, "Binding ctl for '%s'",
-				snd_ctl_elem_info_get_name(state->bound_ctls[i].info));
-	}
+	fetch_bind_ctls(state);
 }
 
 int spa_alsa_init(struct state *state, const struct spa_dict *info)