On Wed, 11 Oct 2017 08:36:13 +0200, Kuninori Morimoto wrote:
From: Takashi Iwai tiwai@suse.de
In case of user unbind ALSA driver during playbacking/capturing, each driver needs to stop and remove it correctly. One note here is that we can't cancel from remove function in such case, becasue unbind operation doesn't check return value from remove function. So, we *must* stop and remove in this case.
For this purpose, we need to sync (= wait) until the all top-level operations are canceled at remove function. For example, snd_card_free() processes the isconnection procedure at
disconnection
first, then waits for the completion. That's how the hot-unplug works safely. It's implemented, at least, in the top-level driver removal.
Now for the lower level driver, we need a similar strategy. Notify to the toplevel for hot-unplug (disconnect in ALSA), and sync with the stop operation, then continue the rest of its own remove procedure.
This patch adds snd_card_disconnect_sync(), and driver can use it from remove function.
Signed-off-by: Takashi Iwai tiwai@suse.de Tested-by: Kuninori Morimoto kuninori.morimoto.gx@renesas.com
Takashi-san
I created this patch and its git-log, but please fixup it if needed.
I would split this again to two patches, one for adding snd_card_disconnect_sync(), and another for adding snd_pcm_stop() call at snd_pcm_dev_disconnect().
Basically the latter is for the drivers that don't handle the PCM stop at disconnection explicitly, and it's not mandatory when the driver's pcm dev_disconnect callback handles it.
Also, since these changes are about ALSA core, and at least the PCM-stop one is intrusive and may have influences on the behavior of other drivers, I'd like to test with usb-audio before landing to ASoC world. Once when confirmed, I'll publish a persistent branch containing these API changes and let Mark pull it.
More comments below:
include/sound/core.h | 2 ++ sound/core/init.c | 18 ++++++++++++++++++ sound/core/pcm.c | 4 ++++ 3 files changed, 24 insertions(+)
diff --git a/include/sound/core.h b/include/sound/core.h index 4104a9d..5f181b8 100644 --- a/include/sound/core.h +++ b/include/sound/core.h @@ -133,6 +133,7 @@ struct snd_card { struct device card_dev; /* cardX object for sysfs */ const struct attribute_group *dev_groups[4]; /* assigned sysfs attr */ bool registered; /* card_dev is registered? */
- wait_queue_head_t remove_sleep;
#ifdef CONFIG_PM unsigned int power_state; /* power state */ @@ -240,6 +241,7 @@ int snd_card_new(struct device *parent, int idx, const char *xid, struct snd_card **card_ret);
int snd_card_disconnect(struct snd_card *card); +void snd_card_disconnect_sync(struct snd_card *card); int snd_card_free(struct snd_card *card); int snd_card_free_when_closed(struct snd_card *card); void snd_card_set_id(struct snd_card *card, const char *id); diff --git a/sound/core/init.c b/sound/core/init.c index 32ebe2f..f7f7050 100644 --- a/sound/core/init.c +++ b/sound/core/init.c @@ -255,6 +255,7 @@ int snd_card_new(struct device *parent, int idx, const char *xid, #ifdef CONFIG_PM init_waitqueue_head(&card->power_sleep); #endif
init_waitqueue_head(&card->remove_sleep);
device_initialize(&card->card_dev); card->card_dev.parent = parent;
@@ -452,6 +453,21 @@ int snd_card_disconnect(struct snd_card *card) } EXPORT_SYMBOL(snd_card_disconnect);
+void snd_card_disconnect_sync(struct snd_card *card)
We need the documentation for the public API function.
+{
- DECLARE_COMPLETION(comp);
This completion isn't used here, no?
- if (snd_card_disconnect(card) < 0)
return;
OK, we should bail out here, but since we can't handle the error, it's better to warn explicitly. Not necessarily WARN_ON() but give a fat error message.
thanks,
Takashi
- spin_lock_irq(&card->files_lock);
- wait_event_lock_irq(card->remove_sleep,
list_empty(&card->files_list),card->files_lock);- spin_unlock_irq(&card->files_lock);
+} +EXPORT_SYMBOL_GPL(snd_card_disconnect_sync);
static int snd_card_do_free(struct snd_card *card) { #if IS_ENABLED(CONFIG_SND_MIXER_OSS) @@ -957,6 +973,8 @@ int snd_card_file_remove(struct snd_card *card, struct file *file) break; } }
- if (list_empty(&card->files_list))
wake_up_all(&card->remove_sleep);diff --git a/sound/core/pcm.c b/sound/core/pcm.c index 7eadb7f..054e47a 100644 --- a/sound/core/pcm.c +++ b/sound/core/pcm.c @@ -1152,6 +1152,10 @@ static int snd_pcm_dev_disconnect(struct snd_device *device) for (substream = pcm->streams[cidx].substream; substream; substream = substream->next) { snd_pcm_stream_lock_irq(substream); if (substream->runtime) {
if (snd_pcm_running(substream))snd_pcm_stop(substream,SNDRV_PCM_STATE_DISCONNECTED);/* to be sure, set the state unconditionally */ substream->runtime->status->state = SNDRV_PCM_STATE_DISCONNECTED; wake_up(&substream->runtime->sleep); wake_up(&substream->runtime->tsleep);-- 1.9.1