ALSA: pcm: oss: Use guard() for setup

The setup_mutex in PCM oss code can be simplified with guard().
(params_lock is tough and not trivial to covert, though.)

Only the code refactoring, and no functional changes.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20240227085306.9764-24-tiwai@suse.de

sound/core/oss/pcm_oss.c

@@ -2333,7 +2333,7 @@ static void snd_pcm_oss_look_for_setup(struct snd_pcm *pcm, int stream,
 {
 	struct snd_pcm_oss_setup *setup;
 
-	mutex_lock(&pcm->streams[stream].oss.setup_mutex);
+	guard(mutex)(&pcm->streams[stream].oss.setup_mutex);
 	do {
 		for (setup = pcm->streams[stream].oss.setup_list; setup;
 		     setup = setup->next) {
@@ -2344,7 +2344,6 @@ static void snd_pcm_oss_look_for_setup(struct snd_pcm *pcm, int stream,
  out:
 	if (setup)
 		*rsetup = *setup;
-	mutex_unlock(&pcm->streams[stream].oss.setup_mutex);
 }
 
 static void snd_pcm_oss_release_substream(struct snd_pcm_substream *substream)
@@ -2950,7 +2949,7 @@ static void snd_pcm_oss_proc_read(struct snd_info_entry *entry,
 {
 	struct snd_pcm_str *pstr = entry->private_data;
 	struct snd_pcm_oss_setup *setup = pstr->oss.setup_list;
-	mutex_lock(&pstr->oss.setup_mutex);
+	guard(mutex)(&pstr->oss.setup_mutex);
 	while (setup) {
 		snd_iprintf(buffer, "%s %u %u%s%s%s%s%s%s\n",
 			    setup->task_name,
@@ -2964,7 +2963,6 @@ static void snd_pcm_oss_proc_read(struct snd_info_entry *entry,
 			    setup->nosilence ? " no-silence" : "");
 		setup = setup->next;
 	}
-	mutex_unlock(&pstr->oss.setup_mutex);
 }
 
 static void snd_pcm_oss_proc_free_setup_list(struct snd_pcm_str * pstr)
@@ -2990,12 +2988,11 @@ static void snd_pcm_oss_proc_write(struct snd_info_entry *entry,
 	struct snd_pcm_oss_setup *setup, *setup1, template;
 
 	while (!snd_info_get_line(buffer, line, sizeof(line))) {
-		mutex_lock(&pstr->oss.setup_mutex);
+		guard(mutex)(&pstr->oss.setup_mutex);
 		memset(&template, 0, sizeof(template));
 		ptr = snd_info_get_str(task_name, line, sizeof(task_name));
 		if (!strcmp(task_name, "clear") || !strcmp(task_name, "erase")) {
 			snd_pcm_oss_proc_free_setup_list(pstr);
-			mutex_unlock(&pstr->oss.setup_mutex);
 			continue;
 		}
 		for (setup = pstr->oss.setup_list; setup; setup = setup->next) {
@@ -3035,7 +3032,6 @@ static void snd_pcm_oss_proc_write(struct snd_info_entry *entry,
 			setup = kmalloc(sizeof(*setup), GFP_KERNEL);
 			if (! setup) {
 				buffer->error = -ENOMEM;
-				mutex_unlock(&pstr->oss.setup_mutex);
 				return;
 			}
 			if (pstr->oss.setup_list == NULL)
@@ -3049,12 +3045,10 @@ static void snd_pcm_oss_proc_write(struct snd_info_entry *entry,
 			if (! template.task_name) {
 				kfree(setup);
 				buffer->error = -ENOMEM;
-				mutex_unlock(&pstr->oss.setup_mutex);
 				return;
 			}
 		}
 		*setup = template;
-		mutex_unlock(&pstr->oss.setup_mutex);
 	}
 }