nixpkgs/pkgs/os-specific/linux/alsa-lib/alsa-plugin-dirs.patch

diff --git a/src/pcm/pcm.c b/src/pcm/pcm.c
index 74d1d1a..17ffb12 100644
--- a/src/pcm/pcm.c
+++ b/src/pcm/pcm.c
@@ -2042,6 +2042,19 @@ static const char *const build_in_pcms[] = {
 	NULL
 };
 
+
+// helper funcion used below
+int file_exists(const char * filename)
+{
+	FILE * file;
+	if (file = fopen(filename, "r"))
+	{
+		fclose(file);
+		return 1;
+	}
+	return 0;
+}
+
 static int snd_pcm_open_conf(snd_pcm_t **pcmp, const char *name,
 			     snd_config_t *pcm_root, snd_config_t *pcm_conf,
 			     snd_pcm_stream_t stream, int mode)
@@ -2141,8 +2154,38 @@ static int snd_pcm_open_conf(snd_pcm_t **pcmp, const char *name,
 				err = -ENOMEM;
 				goto _err;
 			}
-			lib = buf1;
 			sprintf(buf1, "%s/libasound_module_pcm_%s.so", ALSA_PLUGIN_DIR, str);
+			if (!file_exists(buf1)){
+				// try to locate plugin in one of ALSA_PLUGIN_DIRS which is colon separated list of paths
+				char * pdirs = getenv("ALSA_PLUGIN_DIRS");
+
+				if (pdirs){ // env var set?
+					char * saveptr;
+					while (1) {
+						char * dir_tok = strtok_r(pdirs, "::::", &saveptr); // "::::" to work around bug in glibc and -O2 ? ":" seems to cause a segfault
+						if (dir_tok == NULL)
+                            break;
+						char * so_file = malloc(strlen(str) + strlen(dir_tok) + 32);
+						if (so_file == NULL) {
+							err = -ENOMEM;
+							goto _err;
+						}
+
+						sprintf(so_file, "%s/libasound_module_pcm_%s.so", dir_tok, str);
+
+						if (file_exists(so_file)){
+
+							free(buf1);
+							buf1 = so_file;
+							break;
+						} else {
+							free (so_file);
+						}
+						pdirs = NULL;
+					}
+				}
+			}
+			lib = buf1;
 		}
 	}
 #ifndef PIC


diff --git a/src/control/control.c b/src/control/control.c
index c090797..137fe57 100644
--- a/src/control/control.c
+++ b/src/control/control.c
@@ -854,8 +854,38 @@ static int snd_ctl_open_conf(snd_ctl_t **ctlp, const char *name,
 				err = -ENOMEM;
 				goto _err;
 			}
+			sprintf(buf1, "%s/libasound_module_pcm_%s.so", ALSA_PLUGIN_DIR, str);
+			if (!file_exists(buf1)){
+				// try to locate plugin in one of ALSA_PLUGIN_DIRS which is colon separated list of paths
+				char * pdirs = getenv("ALSA_PLUGIN_DIRS");
+
+				if (pdirs){ // env var set?
+					char * saveptr;
+					while (1) {
+						char * dir_tok = strtok_r(pdirs, "::::", &saveptr); // "::::" to work around bug in glibc and -O2 ? ":" seems to cause a segfault
+						if (dir_tok == NULL)
+                            break;
+						char * so_file = malloc(strlen(str) + strlen(dir_tok) + 32);
+						if (so_file == NULL) {
+							err = -ENOMEM;
+							goto _err;
+						}
+
+						sprintf(so_file, "%s/libasound_module_ctl_%s.so", dir_tok, str);
+
+						if (file_exists(so_file)){
+
+							free(buf1);
+							buf1 = so_file;
+							break;
+						} else {
+							free (so_file);
+						}
+						pdirs = NULL;
+					}
+				}
+			}
 			lib = buf1;
-			sprintf(buf1, "%s/libasound_module_ctl_%s.so", ALSA_PLUGIN_DIR, str);
 		}
 	}
 #ifndef PIC