kernel/linux.git/sound/core/init.c, branch v6.0

ALSA: core: Fix double-free at snd_card_new()

2022-09-19T12:36:06+00:00

During the code change to add the support for devres-managed card instance, we put an explicit kfree(card) call at the error path in snd_card_new(). This is needed for the early error path before the card is initialized with the device, but is rather superfluous and causes a double-free at the error path after the card instance is initialized, as the destructor of the card object already contains a kfree() call. This patch fixes the double-free situation by removing the superfluous kfree(). Meanwhile we need to call kfree() explicitly for the early error path, so it's added there instead. Fixes: e8ad415b7a55 ("ALSA: core: Add managed card creation") Reported-by: Rondreis Cc: Link: https://lore.kernel.org/r/CAB7eexL1zBnB636hwS27d-LdPYZ_R1-5fJS_h=ZbCWYU=UPWJg@mail.gmail.com Link: https://lore.kernel.org/r/20220919123516.28222-1-tiwai@suse.de Signed-off-by: Takashi Iwai

ALSA: core: Replace scnprintf() with sysfs_emit()

2022-08-02T14:03:45+00:00

sysfs_emit() is a new helper to simplify the sysfs string output. Replace the open-code with this new helper. Link: https://lore.kernel.org/r/20220801165639.26030-5-tiwai@suse.de Signed-off-by: Takashi Iwai

ALSA: core: Fix missing return value comments for kernel docs

2022-07-13T11:42:38+00:00

Each kernel doc comment expects the definition of the return value in a proper format. This patch adds or fixes the missing entries for the remaining ALSA core API functions. Link: https://lore.kernel.org/r/20220713104759.4365-8-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: Simplify snd_power_ref_and_wait() with the standard macro

2022-01-19T16:26:04+00:00

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 Link: https://lore.kernel.org/r/20220119091050.30125-1-tiwai@suse.de Signed-off-by: Takashi Iwai

ALSA: core: Fix double calls of snd_card_free() via devres

2021-07-31T08:36:06+00:00

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

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

ALSA: core: Fix assignment in if condition

2021-06-09T15:30:22+00:00

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

ALSA: core: use DEVICE_ATTR_*() macro

2021-05-28T14:32:11+00:00

Use DEVICE_ATTR_*() helper instead of plain DEVICE_ATTR, which makes the code a bit shorter and easier to read. Signed-off-by: YueHaibing Link: https://lore.kernel.org/r/20210526121828.8460-1-yuehaibing@huawei.com Signed-off-by: Takashi Iwai