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ucm: allow passing variables through ucm open string

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It is useful to pass information like application capabilities
to the UCM configuration parser. Those variables are prefixed
with '@' for the configuration files.

An example:

   "<<<v1='a b c',x=12>>>hw:1"

Variables can substituted in the configuration:

   "${var:@v1}" -> "a b c"
   "${var:@x}" -> 12

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
This commit is contained in:
Jaroslav Kysela 2022-05-16 13:16:01 +02:00
parent 46e991c9ce
commit 11ec9e497e
2 changed files with 63 additions and 0 deletions
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54
src/ucm/main.c
View file

@ -1356,6 +1356,57 @@ static int set_device(snd_use_case_mgr_t *uc_mgr,
return err;
}
/**
* \brief Parse open arguments
* \param uc_mgr Use case manager
* \param name name of card to open
* \return the rest of the card name to open
*/
const char *parse_open_variables(snd_use_case_mgr_t *uc_mgr, const char *name)
{
const char *end, *id;
char *args, *var;
snd_config_t *cfg, *n;
snd_config_iterator_t i, next;
char vname[128];
size_t l;
int err;
end = strstr(name, ">>>");
if (end == NULL)
return name;
l = end - name - 3;
args = alloca(l + 1);
strncpy(args, name + 3, l);
args[l] = '\0';
err = snd_config_load_string(&cfg, args, 0);
if (err < 0) {
uc_error("error: open arguments are not valid (%s)", args);
goto skip;
}
/* set arguments */
snd_config_for_each(i, next, cfg) {
n = snd_config_iterator_entry(i);
err = snd_config_get_id(n, &id);
if (err < 0)
goto skip;
err = snd_config_get_ascii(n, &var);
if (err < 0)
goto skip;
snprintf(vname, sizeof(vname), "@%s", id);
err = uc_mgr_set_variable(uc_mgr, vname, var);
free(var);
if (err < 0)
goto skip;
}
snd_config_delete(cfg);
skip:
return end + 3;
}
/**
* \brief Init sound card use case manager.
* \param uc_mgr Returned use case manager pointer
@ -1388,6 +1439,9 @@ int snd_use_case_mgr_open(snd_use_case_mgr_t **uc_mgr,
mgr->suppress_nodev_errors = 1;
}
if (card_name[0] == '<' && card_name[1] == '<' && card_name[2] == '<')
card_name = parse_open_variables(mgr, card_name);
err = uc_mgr_card_open(mgr);
if (err < 0) {
uc_mgr_free(mgr);

9
src/ucm/parser.c
View file

@ -278,6 +278,10 @@ static int evaluate_regex(snd_use_case_mgr_t *uc_mgr,
err = snd_config_get_id(n, &id);
if (err < 0)
return err;
if (id[0] == '@') {
uc_error("error: value names starting with '@' are reserved for application variables");
return -EINVAL;
}
err = uc_mgr_define_regex(uc_mgr, id, n);
if (err < 0)
return err;
@ -327,6 +331,11 @@ static int evaluate_define(snd_use_case_mgr_t *uc_mgr,
free(var);
if (err < 0)
return err;
if (id[0] == '@') {
free(s);
uc_error("error: value names starting with '@' are reserved for application variables");
return -EINVAL;
}
err = uc_mgr_set_variable(uc_mgr, id, s);
free(s);
if (err < 0)