This is a small helper function to handle the error path more easily
when an error happens during the probe for the device with the
device-managed card.  Since devres releases in the reverser order of
the creations, usually snd_card_free() gets called at the last in the
probe error path unless it already reached snd_card_register() calls.
Due to this nature, when a driver expects the resource releases in
card->private_free, this might be called too lately.

As a workaround, one should call the probe like:

 static int __some_probe(...) { // do real probe.... }

 static int some_probe(...)
 {
	return snd_card_free_on_error(dev, __some_probe(dev, ...));
 }

so that the snd_card_free() is called explicitly at the beginning of
the error path from the probe.

This function will be used in the upcoming fixes to address the
regressions by devres usages.

Fixes: e8ad415b7a55 ("ALSA: core: Add managed card creation")
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20220412093141.8008-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Use wait_event_cmd() macro and simplify snd_power_ref_wait()
implementation.  This may also cover possible races in the current
open code, too.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20220119091050.30125-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

At the transition to the devres-managed card release, we've put the
check of double-free at trigger_card_release().  But this wasn't
enough, as the code path calls snd_card_free() again, and it would
lead to the doubly snd_card_free() calls.

Actually the v1 patch was correct to handle this, but I forgot that
corner case and moved the check to the more obvious place as I thought
it's clearer.  But, as usual, devils live in details.

This patch corrects the check of the double-free to the right place,
with a bit more comments.

Fixes: e8ad415b7a55 ("ALSA: core: Add managed card creation")
Link: https://lore.kernel.org/r/20210731083446.26680-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

As a second step for preliminary to widen the devres usages among
sound drivers, this patch adds a new ALSA core API function,
snd_devm_card_new(), to create a snd_card object via devres.
When a card object is created by this new function, snd_card_free() is
called automatically and the card object resource gets released at the
device unbinding time.

However, the story isn't that simple.  A caveat is that we have to
call snd_card_free() at the very first of the whole resource release
procedure, in order to assure that the all exposed devices on
user-space are deleted and sync with processes accessing those devices
before releasing resources.

For achieving it, snd_card_register() adds a new devres action to
trigger snd_card_free() automatically when the given card object is a
"managed" one.  Since usually snd_card_register() is the last step of
the initialization, this should work in most cases.

With all these tricks, some drivers can get rid of the whole driver
remove callback code.

About a bit of implementation details: the patch adds two new flags to
snd_card object: managed and releasing.  The former indicates that the
object was created via snd_devm_card_new(), and the latter is used for
avoiding the double-free of snd_card_free() calls.  Both flags are
fairly internal and likely uninteresting to normal users.

Link: https://lore.kernel.org/r/20210715075941.23332-3-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

There are a few places doing assignments in if condition in ALSA core
code, which is a bad coding style that may confuse readers and
occasionally lead to bugs.

This patch is merely for coding-style fixes, no functional changes.

Link: https://lore.kernel.org/r/20210608140540.17885-54-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Use DEVICE_ATTR_*() helper instead of plain DEVICE_ATTR,
which makes the code a bit shorter and easier to read.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20210526121828.8460-1-yuehaibing@huawei.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

The power_state argument of snd_power_wait() is superfluous, receiving
only SNDRV_POWER_STATE_D0.  Let's drop it in all callers for
simplicity.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210523090920.15345-6-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Although the power state check is performed in various places (e.g. at
the entrance of quite a few ioctls), there can be still some pending
tasks that already went into the ioctl handler or other ops, and those
may access the hardware even after the power state check.  For
example, kcontrol access ioctl paths that call info/get/put callbacks
may update the hardware registers.  If a system wants to assure the
free from such hw access (like the case of PCI rescan feature we're
going to implement in future), this situation must be avoided, and we
have to sync such in-flight tasks finishing beforehand.

For that purpose, this patch introduces a few new things in core code:
- A refcount, power_ref, and a wait queue, power_ref_sleep, to the
  card object
- A few new helpers, snd_power_ref(), snd_power_unref(),
  snd_power_ref_and_wait(), and snd_power_sync_ref()

In the code paths that call kctl info/read/write/tlv ops, we check the
power state with the newly introduced snd_power_ref_and_wait().  This
function also takes the card.power_ref refcount for tracking this
in-flight task.  Once after the access finishes, snd_power_unref() is
called to released the refcount in return.  So the driver can sync via
snd_power_sync_ref() assuring that all in-flight tasks have been
finished.

As of this patch, snd_power_sync_ref() is called only at
snd_card_disconnect(), but it'll be used in other places in future.

Note that atomic_t is used for power_ref intentionally instead of
refcount_t.  It's because of the design of refcount_t type; refcount_t
cannot be zero-based, and it cannot do dec_and_test() call for
multiple times, hence it's not suitable for our purpose.

Also, this patch changes snd_power_wait() to accept only
SNDRV_CTL_POWER_D0, which is the only value that makes sense.
In later patch, the snd_power_wait() calls will be cleaned up.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20210523090920.15345-3-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

modification in commit 2a3f7221acdd ("ALSA: core: Fix card races between
register and disconnect") resulting in this problem.

Fixes: 2a3f7221acdd ("ALSA: core: Fix card races between register and disconnect")
Signed-off-by: Jia Zhou <zhou.jia2@zte.com.cn>
Signed-off-by: Yi Wang <wang.yi59@zte.com.cn>
Link: https://lore.kernel.org/r/1616989007-34429-1-git-send-email-wang.yi59@zte.com.cn
Signed-off-by: Takashi Iwai <tiwai@suse.de>

The PCM core should perform the sync for the pending stop operations
at disconnection.  Otherwise it may lead to unexpected access.

Currently the old user of sync_stop, USB-audio driver, has its own
sync, so this isn't needed, but it's better to guarantee the sync in
the PCM core level.

This patch adds the missing sync_stop call at PCM disconnection
callback.  It also assures the IRQ sync if it's specified in the
card.  snd_pcm_sync_stop() is slightly modified to be called also for
any PCM substream object now.

Fixes: 1e850beea278 ("ALSA: pcm: Add the support for sync-stop operation")
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210206203656.15959-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>