Commit e8ad415b authored by Takashi Iwai's avatar Takashi Iwai
Browse files

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: default avatarTakashi Iwai <tiwai@suse.de>
parent 427ae268

include/sound/core.h

+5 −0
Original line number Diff line number Diff line
@@ -117,6 +117,8 @@ 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? */

	bool managed;			/* managed via devres */

	bool releasing;			/* during card free process */

	int sync_irq;			/* assigned irq, used for PCM sync */

	wait_queue_head_t remove_sleep;
@@ -274,6 +276,9 @@ extern int (*snd_mixer_oss_notify_callback)(struct snd_card *card, int cmd); 
int snd_card_new(struct device *parent, int idx, const char *xid,

		 struct module *module, int extra_size,

		 struct snd_card **card_ret);

int snd_devm_card_new(struct device *parent, int idx, const char *xid,

		      struct module *module, size_t extra_size,

		      struct snd_card **card_ret);



int snd_card_disconnect(struct snd_card *card);

void snd_card_disconnect_sync(struct snd_card *card);

sound/core/init.c

+91 −8
Original line number Diff line number Diff line
@@ -134,6 +134,9 @@ void snd_device_initialize(struct device *dev, struct snd_card *card) 
}

EXPORT_SYMBOL_GPL(snd_device_initialize);



static int snd_card_init(struct snd_card *card, struct device *parent,

			 int idx, const char *xid, struct module *module,

			 size_t extra_size);

static int snd_card_do_free(struct snd_card *card);

static const struct attribute_group card_dev_attr_group;
@@ -163,9 +166,6 @@ int snd_card_new(struct device *parent, int idx, const char *xid, 
{

	struct snd_card *card;

	int err;

#ifdef CONFIG_SND_DEBUG

	char name[8];

#endif



	if (snd_BUG_ON(!card_ret))

		return -EINVAL;
@@ -176,6 +176,74 @@ int snd_card_new(struct device *parent, int idx, const char *xid, 
	card = kzalloc(sizeof(*card) + extra_size, GFP_KERNEL);

	if (!card)

		return -ENOMEM;



	err = snd_card_init(card, parent, idx, xid, module, extra_size);

	if (err < 0) {

		kfree(card);

		return err;

	}



	*card_ret = card;

	return 0;

}

EXPORT_SYMBOL(snd_card_new);



static void __snd_card_release(struct device *dev, void *data)

{

	snd_card_free(data);

}



/**

 * snd_devm_card_new - managed snd_card object creation

 * @parent: the parent device object

 * @idx: card index (address) [0 ... (SNDRV_CARDS-1)]

 * @xid: card identification (ASCII string)

 * @module: top level module for locking

 * @extra_size: allocate this extra size after the main soundcard structure

 * @card_ret: the pointer to store the created card instance

 *

 * This function works like snd_card_new() but manages the allocated resource

 * via devres, i.e. you don't need to free explicitly.

 *

 * When a snd_card object is created with this function and registered via

 * snd_card_register(), the very first devres action to call snd_card_free()

 * is added automatically.  In that way, the resource disconnection is assured

 * at first, then released in the expected order.

 */

int snd_devm_card_new(struct device *parent, int idx, const char *xid,

		      struct module *module, size_t extra_size,

		      struct snd_card **card_ret)

{

	struct snd_card *card;

	int err;



	*card_ret = NULL;

	card = devres_alloc(__snd_card_release, sizeof(*card) + extra_size,

			    GFP_KERNEL);

	if (!card)

		return -ENOMEM;

	card->managed = true;

	err = snd_card_init(card, parent, idx, xid, module, extra_size);

	if (err < 0) {

		devres_free(card);

		return err;

	}



	devres_add(parent, card);

	*card_ret = card;

	return 0;

}

EXPORT_SYMBOL_GPL(snd_devm_card_new);



static int snd_card_init(struct snd_card *card, struct device *parent,

			 int idx, const char *xid, struct module *module,

			 size_t extra_size)

{

	int err;

#ifdef CONFIG_SND_DEBUG

	char name[8];

#endif



	if (extra_size > 0)

		card->private_data = (char *)card + sizeof(struct snd_card);

	if (xid)
@@ -197,7 +265,6 @@ int snd_card_new(struct device *parent, int idx, const char *xid, 
		mutex_unlock(&snd_card_mutex);

		dev_err(parent, "cannot find the slot for index %d (range 0-%i), error: %d\n",

			 idx, snd_ecards_limit - 1, err);

		kfree(card);

		return err;

	}

	set_bit(idx, snd_cards_lock);		/* lock it */
@@ -256,8 +323,6 @@ int snd_card_new(struct device *parent, int idx, const char *xid, 
	sprintf(name, "card%d", idx);

	card->debugfs_root = debugfs_create_dir(name, sound_debugfs_root);

#endif



	*card_ret = card;

	return 0;



      __error_ctl:
@@ -266,7 +331,6 @@ int snd_card_new(struct device *parent, int idx, const char *xid, 
	put_device(&card->card_dev);

  	return err;

}

EXPORT_SYMBOL(snd_card_new);



/**

 * snd_card_ref - Get the card object from the index
@@ -481,6 +545,7 @@ EXPORT_SYMBOL_GPL(snd_card_disconnect_sync); 


static int snd_card_do_free(struct snd_card *card)

{

	card->releasing = true;

#if IS_ENABLED(CONFIG_SND_MIXER_OSS)

	if (snd_mixer_oss_notify_callback)

		snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_FREE);
@@ -498,6 +563,7 @@ static int snd_card_do_free(struct snd_card *card) 
#endif

	if (card->release_completion)

		complete(card->release_completion);

	if (!card->managed)

		kfree(card);

	return 0;

}
@@ -745,6 +811,14 @@ int snd_card_add_dev_attr(struct snd_card *card, 
}

EXPORT_SYMBOL_GPL(snd_card_add_dev_attr);



static void trigger_card_free(void *data)

{

	struct snd_card *card = data;



	if (!card->releasing)

		snd_card_free(data);

}



/**

 *  snd_card_register - register the soundcard

 *  @card: soundcard structure
@@ -768,6 +842,15 @@ int snd_card_register(struct snd_card *card) 
		if (err < 0)

			return err;

		card->registered = true;

	} else {

		if (card->managed)

			devm_remove_action(card->dev, trigger_card_free, card);

	}



	if (card->managed) {

		err = devm_add_action(card->dev, trigger_card_free, card);

		if (err < 0)

			return err;

	}



	err = snd_device_register_all(card);