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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>
This commit is contained in:
Takashi Iwai 2021-07-15 09:58:24 +02:00
parent 427ae2689d
commit e8ad415b7a
2 changed files with 96 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/sound/core.h
View File

@ -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);

99
sound/core/init.c
View File

@ -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);
@ -498,7 +563,8 @@ static int snd_card_do_free(struct snd_card *card)
#endif
if (card->release_completion)
complete(card->release_completion);
kfree(card);
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);