void pa_alsa_profile_set_probe(
pa_alsa_profile_set *ps, // ALSA 音频配置集合
const char *dev_id, // 设备标识符
const pa_sample_spec *ss, // 采样规格
unsigned default_n_fragments, // 默认分片数
unsigned default_fragment_size_msec) { // 默认分片大小（毫秒）
bool found_output = false, found_input = false; // 是否找到输出和输入配置
pa_alsa_profile *p, *last = NULL; // 当前配置和上一个配置
pa_alsa_profile **pp, **probe_order; // 配置探测顺序数组
pa_alsa_mapping *m; // ALSA 映射
pa_hashmap *broken_inputs, *broken_outputs, *used_paths; // 存储损坏输入、损坏输出和已使用路径的哈希映射
pa_alsa_mapping *selected_fallback_input = NULL, *selected_fallback_output = NULL; // 选定的回退输入和输出映射
pa_assert(ps); // 断言配置集合存在
pa_assert(dev_id); // 断言设备标识符存在
pa_assert(ss); // 断言采样规格存在
// 创建哈希映射来存储损坏的输入、输出和已使用的路径
broken_inputs = pa_hashmap_new(pa_idxset_trivial_hash_func, pa_idxset_trivial_compare_func);
broken_outputs = pa_hashmap_new(pa_idxset_trivial_hash_func, pa_idxset_trivial_compare_func);
used_paths = pa_hashmap_new(pa_idxset_trivial_hash_func, pa_idxset_trivial_compare_func);
// 创建用于指示探测顺序的 probe_order 数组
pp = probe_order = pa_xnew0(pa_alsa_profile *, pa_hashmap_size(ps->profiles) + 1);
// 将配置按一定的优先级顺序添加到探测顺序中
pp += add_profiles_to_probe(pp, ps->profiles, false, false);
pp += add_profiles_to_probe(pp, ps->profiles, false, true);
pp += add_profiles_to_probe(pp, ps->profiles, true, false);
pp += add_profiles_to_probe(pp, ps->profiles, true, true);
// 遍历探测顺序中的配置
for (pp = probe_order; *pp; pp++) {
uint32_t idx;
p = *pp;
// 跳过已经找到的回退配置，但仍然探测已选的回退配置
if (found_input && p->fallback_input)
if (selected_fallback_input == NULL || pa_idxset_get_by_index(p->input_mappings, 0) != selected_fallback_input)
continue;
if (found_output && p->fallback_output)
if (selected_fallback_output == NULL || pa_idxset_get_by_index(p->output_mappings, 0) != selected_fallback_output)
continue;
// 跳过已经标记为支持的配置
if (!p->supported) {
// 最终化配置探测
profile_finalize_probing(last, p);
p->supported = true;
// 检查输出映射是否能够打开
if (p->output_mappings) {
PA_IDXSET_FOREACH(m, p->output_mappings, idx) {
if (pa_hashmap_get(broken_outputs, m) == m) {
// 标记为不支持的配置
pa_log_debug("Skipping profile %s - will not be able to open output:%s", p->name, m->name);
p->supported = false;
break;
}
}
}
// 检查输入映射是否能够打开
if (p->input_mappings && p->supported) {
PA_IDXSET_FOREACH(m, p->input_mappings, idx) {
if (pa_hashmap_get(broken_inputs, m) == m) {
// 标记为不支持的配置
pa_log_debug("Skipping profile %s - will not be able to open input:%s", p->name, m->name);
p->supported = false;
break;
}
}
}
if (p->supported)
pa_log_debug("Looking at profile %s", p->name);
// 检查是否可以打开所有新的映射
if (p->output_mappings && p->supported)
PA_IDXSET_FOREACH(m, p->output_mappings, idx) {
// 检查是否已经打开
if (m->output_pcm)
continue;
// 尝试打开 PCM 设备
pa_log_debug("Checking for playback on %s (%s)", m->description, m->name);
if (!(m->output_pcm = mapping_open_pcm(m, ss, dev_id, m->exact_channels,
SND_PCM_STREAM_PLAYBACK,
default_n_fragments,
default_fragment_size_msec))) {
// 标记为不支持的配置
p->supported = false;
if (pa_idxset_size(p->output_mappings) == 1 &&
((!p->input_mappings) || pa_idxset_size(p->input_mappings) == 0)) {
pa_log_debug("Caching failure to open output:%s", m->name);
pa_hashmap_put(broken_outputs, m, m);
}
break;
}
if (m->hw_device_index < 0)
mapping_query_hw_device(m, m->output_pcm);
}
// 检查输入映射是否能够打开
if (p->input_mappings && p->supported)
PA_IDXSET_FOREACH(m, p->input_mappings, idx) {
// 检查是否已经打开
if (m->input_pcm)
continue;
// 尝试打开 PCM 设备
pa_log_debug("Checking for recording on %s (%s)", m->description, m->name);
if (!(m->input_pcm = mapping_open_pcm(m, ss, dev_id, m->exact_channels,
SND_PCM_STREAM_CAPTURE,
default_n_fragments,
default_fragment_size_msec))) {
// 标记为不支持的配置
p->supported = false;
if (pa_idxset_size(p->input_mappings) == 1 &&
((!p->output_mappings) || pa_idxset_size(p->output_mappings) == 0)) {
pa_log_debug("Caching failure to open input:%s", m->name);
pa_hashmap_put(broken_inputs, m, m);
}
break;
}
if (m->hw_device_index < 0)
mapping_query_hw_device(m, m->input_pcm);
}
last = p;
if (!p->supported)
continue;
}
pa_log_debug("Profile %s supported.", p->name);
// 标记已找到输出和输入配置
if (p->output_mappings)
PA_IDXSET_FOREACH(m, p->output_mappings, idx)
if (m->output_pcm) {
found_output = true;
if (p->fallback_output && selected_fallback_output == NULL) {
selected_fallback_output = m;
}
mapping_paths_probe(m, p, PA_ALSA_DIRECTION_OUTPUT, used_paths);
}
if (p->input_mappings)
PA_IDXSET_FOREACH(m, p->input_mappings, idx)
if (m->input_pcm) {
found_input = true;
if (p->fallback_input && selected_fallback_input == NULL) {
selected_fallback_input = m;
}
mapping_paths_probe(m, p, PA_ALSA_DIRECTION_INPUT, used_paths);
}
}
// 最终化配置探测，清理资源
profile_finalize_probing(last, NULL);
// 丢弃不支持的配置
pa_alsa_profile_set_drop_unsupported(ps);
// 丢弃未使用的路径
paths_drop_unused(ps->input_paths, used_paths);
paths_drop_unused(ps->output_paths, used_paths);
// 释放资源
pa_hashmap_free(broken_inputs);
pa_hashmap_free(broken_outputs);
pa_hashmap_free(used_paths);
pa_xfree(probe_order);
ps->probed = true; // 标记为已完成探测
}