ucm: configuration - allow to define the configuration variables

It may be useful for the library files to use the runtime configuration
variables.

Example:

 Define.Var1 "hw:${CardId},2"
 Value.PlaybackPCM "${var:Var1}"

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

src/ucm/main.c

@@ -966,6 +966,7 @@ int snd_use_case_mgr_open(snd_use_case_mgr_t **uc_mgr,
 	INIT_LIST_HEAD(&mgr->active_modifiers);
 	INIT_LIST_HEAD(&mgr->active_devices);
 	INIT_LIST_HEAD(&mgr->ctl_list);
+	INIT_LIST_HEAD(&mgr->variable_list);
 	pthread_mutex_init(&mgr->mutex, NULL);
 
 	mgr->card_name = strdup(card_name);

src/ucm/parser.c

@@ -193,6 +193,49 @@ int parse_get_safe_id(snd_config_t *n, const char **id)
 	return 0;
 }
 
+/*
+ * Evaluate variable definitions (in-place delete)
+ */
+static int evaluate_define(snd_use_case_mgr_t *uc_mgr,
+			   snd_config_t *cfg)
+{
+	snd_config_iterator_t i, next;
+	snd_config_t *d, *n;
+	const char *id;
+	char *var, *s;
+	int err;
+
+	err = snd_config_search(cfg, "Define", &d);
+	if (err == -ENOENT)
+		return 1;
+	if (err < 0)
+		return err;
+
+	if (snd_config_get_type(d) != SND_CONFIG_TYPE_COMPOUND) {
+		uc_error("compound type expected for Define");
+		return -EINVAL;
+	}
+
+	snd_config_for_each(i, next, d) {
+		n = snd_config_iterator_entry(i);
+		err = snd_config_get_id(n, &id);
+		if (err < 0)
+			return err;
+		err = snd_config_get_ascii(n, &var);
+		if (err < 0)
+			return err;
+		err = uc_mgr_get_substituted_value(uc_mgr, &s, var);
+		free(var);
+		if (err < 0)
+			return err;
+		uc_mgr_set_variable(uc_mgr, id, s);
+		free(s);
+	}
+
+	snd_config_delete(d);
+	return 0;
+}
+
 /*
  * Evaluate include (in-place)
  */
@@ -239,16 +282,20 @@ static int evaluate_condition(snd_use_case_mgr_t *uc_mgr,
 int uc_mgr_evaluate_inplace(snd_use_case_mgr_t *uc_mgr,
 			    snd_config_t *cfg)
 {
-	int err1 = 0, err2 = 0;
+	int err1 = 0, err2 = 0, err3 = 0;
 
-	while (err1 == 0 || err2 == 0) {
-		/* include at first */
-		err1 = evaluate_include(uc_mgr, cfg);
+	while (err1 == 0 || err2 == 0 || err3 == 0) {
+		/* variables at first */
+		err1 = evaluate_define(uc_mgr, cfg);
 		if (err1 < 0)
 			return err1;
-		err2 = evaluate_condition(uc_mgr, cfg);
+		/* include at second */
+		err2 = evaluate_include(uc_mgr, cfg);
 		if (err2 < 0)
 			return err2;
+		err3 = evaluate_condition(uc_mgr, cfg);
+		if (err3 < 0)
+			return err3;
 	}
 	return 0;
 }

src/ucm/ucm_local.h

@@ -239,6 +239,9 @@ struct snd_use_case_mgr {
 	/* locking */
 	pthread_mutex_t mutex;
 
+	/* UCM internal variables defined in configuration files */
+	struct list_head variable_list;
+
 	/* list of opened control devices */
 	struct list_head ctl_list;
 
@@ -289,6 +292,13 @@ void uc_mgr_free_ctl_list(snd_use_case_mgr_t *uc_mgr);
 
 int uc_mgr_add_value(struct list_head *base, const char *key, char *val);
 
+const char *uc_mgr_get_variable(snd_use_case_mgr_t *uc_mgr,
+				const char *name);
+
+int uc_mgr_set_variable(snd_use_case_mgr_t *uc_mgr,
+			const char *name,
+			const char *val);
+
 int uc_mgr_get_substituted_value(snd_use_case_mgr_t *uc_mgr,
 				 char **_rvalue,
 				 const char *value);

src/ucm/ucm_subs.c

@@ -167,6 +167,21 @@ static char *rval_sysfs(snd_use_case_mgr_t *uc_mgr ATTRIBUTE_UNUSED, const char
 	return strdup(path);
 }
 
+static char *rval_var(snd_use_case_mgr_t *uc_mgr, const char *id)
+{
+	const char *v;
+
+	if (uc_mgr->conf_format < 3) {
+		uc_error("variable substitution is supported in v3+ syntax");
+		return NULL;
+	}
+
+	v = uc_mgr_get_variable(uc_mgr, id);
+	if (v)
+		return strdup(v);
+	return NULL;
+}
+
 #define MATCH_VARIABLE(name, id, fcn, empty_ok)				\
 	if (strncmp((name), (id), sizeof(id) - 1) == 0) { 		\
 		rval = fcn(uc_mgr);					\
@@ -224,6 +239,7 @@ int uc_mgr_get_substituted_value(snd_use_case_mgr_t *uc_mgr,
 			MATCH_VARIABLE(value, "${CardComponents}", rval_card_components, true);
 			MATCH_VARIABLE2(value, "${env:", rval_env);
 			MATCH_VARIABLE2(value, "${sys:", rval_sysfs);
+			MATCH_VARIABLE2(value, "${var:", rval_var);
 			err = -EINVAL;
 			tmp = strchr(value, '}');
 			if (tmp) {

src/ucm/utils.c

@@ -552,6 +552,56 @@ int uc_mgr_remove_device(struct use_case_verb *verb, const char *name)
 	return found == 0 ? -ENODEV : 0;
 }
 
+const char *uc_mgr_get_variable(snd_use_case_mgr_t *uc_mgr, const char *name)
+{
+	struct list_head *pos;
+	struct ucm_value *value;
+
+	list_for_each(pos, &uc_mgr->variable_list) {
+		value = list_entry(pos, struct ucm_value, list);
+		if (strcmp(value->name, name) == 0)
+			return value->data;
+	}
+	return NULL;
+}
+
+int uc_mgr_set_variable(snd_use_case_mgr_t *uc_mgr, const char *name,
+			const char *val)
+{
+	struct list_head *pos;
+	struct ucm_value *curr;
+	char *val2;
+
+	list_for_each(pos, &uc_mgr->variable_list) {
+		curr = list_entry(pos, struct ucm_value, list);
+		if (strcmp(curr->name, name) == 0) {
+			val2 = strdup(val);
+			if (val2 == NULL)
+				return -ENOMEM;
+			free(curr->data);
+			curr->data = val2;
+			return 0;
+		}
+	}
+
+	curr = calloc(1, sizeof(struct ucm_value));
+	if (curr == NULL)
+		return -ENOMEM;
+	curr->name = strdup(name);
+	if (curr->name == NULL) {
+		free(curr);
+		return -ENOMEM;
+	}
+	curr->data = strdup(val);
+	if (curr->data == NULL) {
+		free(curr->name);
+		free(curr);
+		return -ENOMEM;
+	}
+	list_add_tail(&curr->list, &uc_mgr->variable_list);
+	return 0;
+}
+
 void uc_mgr_free_verb(snd_use_case_mgr_t *uc_mgr)
 {
 	struct list_head *pos, *npos;
@@ -576,6 +626,7 @@ void uc_mgr_free_verb(snd_use_case_mgr_t *uc_mgr)
 	uc_mgr_free_sequence(&uc_mgr->once_list);
 	uc_mgr_free_sequence(&uc_mgr->default_list);
 	uc_mgr_free_value(&uc_mgr->value_list);
+	uc_mgr_free_value(&uc_mgr->variable_list);
 	free(uc_mgr->comment);
 	free(uc_mgr->conf_dir_name);
 	free(uc_mgr->conf_file_name);