linux.git/include/sound/core.h, branch v6.5

sound: make all 'class' structures const

2023-06-21T05:29:10+00:00

Now that the driver core allows for struct class to be in read-only
memory, making all 'class' structures to be declared at build time
placing them into read-only memory, instead of having to be dynamically
allocated at load time.

Cc: Jaroslav Kysela 
Cc: Takashi Iwai 
Cc: Ivan Orlov 
Cc: Greg Kroah-Hartman 
Cc: Geoff Levand 
Cc: Thierry Reding 
Cc: "Uwe Kleine-König" 
Cc: alsa-devel@alsa-project.org
Suggested-by: Greg Kroah-Hartman 
Signed-off-by: Ivan Orlov 
Signed-off-by: Greg Kroah-Hartman 
Link: https://lore.kernel.org/r/20230620175633.641141-2-gregkh@linuxfoundation.org
Signed-off-by: Takashi Iwai

ALSA: core: update comment on snd_card.controls_rwsem

2023-05-08T07:25:48+00:00

Since commit 5bbb1ab5bd ("control: use counting semaphore as write lock
for ELEM_WRITE operation"), this has been locking the controls including
their values, not just the list of controls.

Signed-off-by: Oswald Buddenhagen 
Link: https://lore.kernel.org/r/20230428095941.1706278-6-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai

ALSA: core: Make snd_card_free() return void

2023-02-08T12:39:27+00:00

The function returns 0 unconditionally. Make it return void instead and
simplify all callers accordingly.

Signed-off-by: Uwe Kleine-König 
Reviewed-by: Jaroslav Kysela 
Reviewed-by: Takashi Sakamoto 
Acked-by: Geoff Levand 
Acked-by: Thierry Reding 
Link: https://lore.kernel.org/r/20230207191907.467756-4-u.kleine-koenig@pengutronix.de
Signed-off-by: Takashi Iwai

ALSA: core: Make snd_card_free_when_closed() return void

2023-02-08T12:39:12+00:00

All callers from other files ignore the return value of this function.
And it can only ever return a non-zero value if the parameter card is NULL.

This cannot happen in snd_card_free() as card was dereferenced just before
snd_card_free_when_closed() is called. So the error handling can be dropped
there.

Signed-off-by: Uwe Kleine-König 
Reviewed-by: Jaroslav Kysela 
Reviewed-by: Takashi Sakamoto 
Acked-by: Geoff Levand 
Acked-by: Thierry Reding 
Link: https://lore.kernel.org/r/20230207191907.467756-3-u.kleine-koenig@pengutronix.de
Signed-off-by: Takashi Iwai

ALSA: core: Make snd_card_disconnect() return void

2023-02-08T12:38:28+00:00

All callers from other files ignore the return value of this function.
And it can only ever return a non-zero value if the parameter card is NULL.

Move the check for card being NULL into snd_card_free_when_closed() to keep
the previous behaviour. Note this isn't necessary for
snd_card_disconnect_sync() because if card was NULL in there the dereference
of card for dev_err() would oops the kernel. Replace this by an oops
triggered by the dereference of card for spin_lock_irq().

Signed-off-by: Uwe Kleine-König 
Reviewed-by: Jaroslav Kysela 
Reviewed-by: Takashi Sakamoto 
Acked-by: Geoff Levand 
Acked-by: Thierry Reding 
Link: https://lore.kernel.org/r/20230207191907.467756-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Takashi Iwai

ALSA: core: Add async signal helpers

2022-07-29T10:57:10+00:00

Currently the call of kill_fasync() from an interrupt handler might
lead to potential spin deadlocks, as spotted by syzkaller.
Unfortunately, it's not so trivial to fix this lock chain as it's
involved with the tasklist_lock that is touched in allover places.

As a temporary workaround, this patch provides the way to defer the
async signal notification in a work.  The new helper functions,
snd_fasync_helper() and snd_kill_faync() are replacements for
fasync_helper() and kill_fasync(), respectively.  In addition,
snd_fasync_free() needs to be called at the destructor of the relevant
file object.

Link: https://lore.kernel.org/r/20220728125945.29533-2-tiwai@suse.de
Signed-off-by: Takashi Iwai

ALSA: control: Use xarray for faster lookups

2022-06-15T05:44:55+00:00

The control elements are managed in a single linked list and we
traverse the whole list for matching each numid or ctl id per every
inquiry of a control element.  This is OK-ish for a small number of
elements but obviously it doesn't scale.  Especially the matching with
the ctl id takes time because it checks each field of the snd_ctl_id
element, e.g. the name string is matched with strcmp().

This patch adds the hash tables with Xarray for improving the lookup
speed of a control element.  There are two xarray tables added to the
card; one for numid and another for ctl id.  For the numid, we use the
numid as the index, while for the ctl id, we calculate a hash key.

The lookup is done via a single xa_load() execution.  As long as the
given control element is found on the Xarray table, that's fine, we
can give back a quick lookup result.  The problem is when no entry
hits on the table, and for this case, we have a slight optimization.
Namely, the driver checks whether we had a collision on Xarray table,
and do a fallback search (linear lookup of the full entries) only if a
hash key collision happened beforehand.
So, in theory, the inquiry for a non-existing element might take still
time even with this patch in a worst case, but this must be pretty
rare.

The feature is enabled via CONFIG_SND_CTL_FAST_LOOKUP, which is turned
on as default.  For simplicity, the option can be turned off only when
CONFIG_EXPERT is set ("You are expert? Then you manage 1000 knobs").

Link: https://lore.kernel.org/r/20211028130027.18764-1-tiwai@suse.de
Link: https://lore.kernel.org/r/20220609180504.775-1-tiwai@suse.de
Link: https://lore.kernel.org/all/cover.1653813866.git.quic_rbankapu@quicinc.com/
Link: https://lore.kernel.org/r/20220610064537.18660-1-tiwai@suse.de
Signed-off-by: Takashi Iwai

ALSA: core: Add snd_card_free_on_error() helper

2022-04-12T09:47:57+00:00

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: 
Link: https://lore.kernel.org/r/20220412093141.8008-2-tiwai@suse.de
Signed-off-by: Takashi Iwai

ALSA: core: Add device-managed request_dma()

2021-07-19T14:16:34+00:00

This patch adds a devres-supported helper for requesting an ISA DMA
channel that will be automatically freed at the device unbinding.
It'll be used by quite a few ISA sound drivers.

Link: https://lore.kernel.org/r/20210715075941.23332-4-tiwai@suse.de
Signed-off-by: Takashi Iwai

ALSA: core: Add managed card creation

2021-07-19T14:16:33+00:00

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