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ALSA: core: Add managed card creation
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>
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@ -117,6 +117,8 @@ struct snd_card {
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struct device card_dev; /* cardX object for sysfs */
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const struct attribute_group *dev_groups[4]; /* assigned sysfs attr */
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bool registered; /* card_dev is registered? */
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bool managed; /* managed via devres */
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bool releasing; /* during card free process */
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int sync_irq; /* assigned irq, used for PCM sync */
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wait_queue_head_t remove_sleep;
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@ -274,6 +276,9 @@ extern int (*snd_mixer_oss_notify_callback)(struct snd_card *card, int cmd);
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int snd_card_new(struct device *parent, int idx, const char *xid,
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struct module *module, int extra_size,
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struct snd_card **card_ret);
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int snd_devm_card_new(struct device *parent, int idx, const char *xid,
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struct module *module, size_t extra_size,
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struct snd_card **card_ret);
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int snd_card_disconnect(struct snd_card *card);
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void snd_card_disconnect_sync(struct snd_card *card);
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@ -134,6 +134,9 @@ void snd_device_initialize(struct device *dev, struct snd_card *card)
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}
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EXPORT_SYMBOL_GPL(snd_device_initialize);
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static int snd_card_init(struct snd_card *card, struct device *parent,
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int idx, const char *xid, struct module *module,
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size_t extra_size);
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static int snd_card_do_free(struct snd_card *card);
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static const struct attribute_group card_dev_attr_group;
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@ -163,9 +166,6 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
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{
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struct snd_card *card;
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int err;
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#ifdef CONFIG_SND_DEBUG
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char name[8];
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#endif
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if (snd_BUG_ON(!card_ret))
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return -EINVAL;
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@ -176,6 +176,74 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
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card = kzalloc(sizeof(*card) + extra_size, GFP_KERNEL);
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if (!card)
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return -ENOMEM;
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err = snd_card_init(card, parent, idx, xid, module, extra_size);
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if (err < 0) {
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kfree(card);
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return err;
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}
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*card_ret = card;
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return 0;
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}
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EXPORT_SYMBOL(snd_card_new);
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static void __snd_card_release(struct device *dev, void *data)
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{
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snd_card_free(data);
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}
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/**
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* snd_devm_card_new - managed snd_card object creation
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* @parent: the parent device object
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* @idx: card index (address) [0 ... (SNDRV_CARDS-1)]
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* @xid: card identification (ASCII string)
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* @module: top level module for locking
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* @extra_size: allocate this extra size after the main soundcard structure
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* @card_ret: the pointer to store the created card instance
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*
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* This function works like snd_card_new() but manages the allocated resource
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* via devres, i.e. you don't need to free explicitly.
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*
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* When a snd_card object is created with this function and registered via
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* snd_card_register(), the very first devres action to call snd_card_free()
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* is added automatically. In that way, the resource disconnection is assured
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* at first, then released in the expected order.
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*/
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int snd_devm_card_new(struct device *parent, int idx, const char *xid,
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struct module *module, size_t extra_size,
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struct snd_card **card_ret)
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{
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struct snd_card *card;
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int err;
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*card_ret = NULL;
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card = devres_alloc(__snd_card_release, sizeof(*card) + extra_size,
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GFP_KERNEL);
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if (!card)
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return -ENOMEM;
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card->managed = true;
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err = snd_card_init(card, parent, idx, xid, module, extra_size);
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if (err < 0) {
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devres_free(card);
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return err;
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}
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devres_add(parent, card);
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*card_ret = card;
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return 0;
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}
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EXPORT_SYMBOL_GPL(snd_devm_card_new);
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static int snd_card_init(struct snd_card *card, struct device *parent,
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int idx, const char *xid, struct module *module,
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size_t extra_size)
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{
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int err;
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#ifdef CONFIG_SND_DEBUG
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char name[8];
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#endif
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if (extra_size > 0)
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card->private_data = (char *)card + sizeof(struct snd_card);
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if (xid)
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@ -197,7 +265,6 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
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mutex_unlock(&snd_card_mutex);
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dev_err(parent, "cannot find the slot for index %d (range 0-%i), error: %d\n",
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idx, snd_ecards_limit - 1, err);
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kfree(card);
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return err;
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}
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set_bit(idx, snd_cards_lock); /* lock it */
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@ -256,8 +323,6 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
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sprintf(name, "card%d", idx);
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card->debugfs_root = debugfs_create_dir(name, sound_debugfs_root);
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#endif
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*card_ret = card;
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return 0;
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__error_ctl:
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@ -266,7 +331,6 @@ int snd_card_new(struct device *parent, int idx, const char *xid,
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put_device(&card->card_dev);
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return err;
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}
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EXPORT_SYMBOL(snd_card_new);
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/**
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* snd_card_ref - Get the card object from the index
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@ -481,6 +545,7 @@ EXPORT_SYMBOL_GPL(snd_card_disconnect_sync);
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static int snd_card_do_free(struct snd_card *card)
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{
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card->releasing = true;
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#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
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if (snd_mixer_oss_notify_callback)
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snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_FREE);
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@ -498,7 +563,8 @@ static int snd_card_do_free(struct snd_card *card)
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#endif
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if (card->release_completion)
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complete(card->release_completion);
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kfree(card);
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if (!card->managed)
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kfree(card);
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return 0;
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}
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@ -745,6 +811,14 @@ int snd_card_add_dev_attr(struct snd_card *card,
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}
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EXPORT_SYMBOL_GPL(snd_card_add_dev_attr);
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static void trigger_card_free(void *data)
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{
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struct snd_card *card = data;
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if (!card->releasing)
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snd_card_free(data);
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}
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/**
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* snd_card_register - register the soundcard
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* @card: soundcard structure
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@ -768,6 +842,15 @@ int snd_card_register(struct snd_card *card)
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if (err < 0)
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return err;
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card->registered = true;
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} else {
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if (card->managed)
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devm_remove_action(card->dev, trigger_card_free, card);
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}
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if (card->managed) {
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err = devm_add_action(card->dev, trigger_card_free, card);
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if (err < 0)
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return err;
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}
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err = snd_device_register_all(card);
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