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alsa: more tapdancing to enumerate physical hardware devices.

Apparently some systems see "hw:", some see "default:" and some see
"sysdefault:" (and maybe others!). My workstation sees both "hw:" and
"sysdefault:" ...

Try to find a prefix we like and prioritize the prefixes we (think) we want
most. If everything else fails, if there's a "default" (not a prefix) device
name, list that by itself so the user gets _something_ here.

If we can't find a prefix we like _and_ there's no "default" device, report
no hardware found at all.
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icculus committed Oct 10, 2016
1 parent 9db5e9a commit ca42373fb5961fef5b6cf333d5128f8627bda4b0
Showing with 37 additions and 13 deletions.
  1. +37 −13 src/audio/alsa/SDL_alsa_audio.c
@@ -773,37 +773,61 @@ ALSA_HotplugThread(void *arg)
ALSA_Device *unseen = devices;
ALSA_Device *seen = NULL;
ALSA_Device *prev;
int i;
const char *match = "default:";
size_t match_len = strlen(match);

/* determine what kind of name to match. Use "hw:" devices if they
exist, otherwise use "default:" */
int i, j;
const char *match = NULL;
int bestmatch = 0xFFFF;
size_t match_len = 0;
int defaultdev = -1;
static const char * const prefixes[] = {
"hw:", "sysdefault:", "default:", NULL
};

/* Apparently there are several different ways that ALSA lists
actual hardware. It could be prefixed with "hw:" or "default:"
or "sysdefault:" and maybe others. Go through the list and see
if we can find a preferred prefix for the system. */
for (i = 0; hints[i]; i++) {
char *name = ALSA_snd_device_name_get_hint(hints[i], "NAME");
if (!name) {
continue;
}

if (SDL_strncmp(name, "hw:", 3) == 0) {
match = "hw:";
match_len = strlen(match);
free(name);
break;
/* full name, not a prefix */
if ((defaultdev == -1) && (SDL_strcmp(name, "default") == 0)) {
defaultdev = i;
}

for (j = 0; prefixes[j]; j++) {
const char *prefix = prefixes[j];
const size_t prefixlen = strlen(prefix);
if (SDL_strncmp(name, prefix, prefixlen) == 0) {
if (j < bestmatch) {
bestmatch = j;
match = prefix;
match_len = prefixlen;
}
}
}

free(name);
}

/* look through the list of device names to find matches */
for (i = 0; hints[i]; i++) {
char *name = ALSA_snd_device_name_get_hint(hints[i], "NAME");
char *name;

/* if we didn't find a device name prefix we like at all... */
if ((!match) && (defaultdev != i)) {
continue; /* ...skip anything that isn't the default device. */
}

name = ALSA_snd_device_name_get_hint(hints[i], "NAME");
if (!name) {
continue;
}

/* only want physical hardware interfaces */
if (SDL_strncmp(name, match, match_len) == 0) {
if (!match || (SDL_strncmp(name, match, match_len) == 0)) {
char *ioid = ALSA_snd_device_name_get_hint(hints[i], "IOID");
const SDL_bool isoutput = (ioid == NULL) || (SDL_strcmp(ioid, "Output") == 0);
const SDL_bool isinput = (ioid == NULL) || (SDL_strcmp(ioid, "Input") == 0);

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