linux/sound/hda/local.h
Takashi Iwai 9780ded39b ALSA: hda: Avoid racy recreation of widget kobjects
The refresh of HD-audio widget sysfs kobjects via
snd_hdac_refresh_widget_sysfs() is slightly racy.
The driver recreates the whole tree from scratch after deleting the
whole.  When CONFIG_DEBUG_KOBJECT_RELEASE option is used, kobject
release doesn't happen immediately but delayed, while the re-creation
of the same named kobject happens soon after invoking kobject_put().
This may end up with the conflicts of duplicated kobjects, as found in
the bug report below.

In this patch, we take another approach to refresh the tree: instead
of recreating the whole tree, just add the new nodes and delete the
non-existing nodes.  Since the refresh happens only once at
initialization, no longer race would happen.

Along with the code change, merge snd_hdac_refresh_widget_sysfs() with
the existing snd_hdac_refresh_widgets() with an additional bool flag
for simplifying the code.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=197307
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2017-10-19 13:58:36 +02:00

36 lines
890 B
C

/*
* Local helper macros and functions for HD-audio core drivers
*/
#ifndef __HDAC_LOCAL_H
#define __HDAC_LOCAL_H
#define get_wcaps(codec, nid) \
snd_hdac_read_parm(codec, nid, AC_PAR_AUDIO_WIDGET_CAP)
/* get the widget type from widget capability bits */
static inline int get_wcaps_type(unsigned int wcaps)
{
if (!wcaps)
return -1; /* invalid type */
return (wcaps & AC_WCAP_TYPE) >> AC_WCAP_TYPE_SHIFT;
}
static inline unsigned int get_wcaps_channels(u32 wcaps)
{
unsigned int chans;
chans = (wcaps & AC_WCAP_CHAN_CNT_EXT) >> 13;
chans = (chans + 1) * 2;
return chans;
}
extern const struct attribute_group *hdac_dev_attr_groups[];
int hda_widget_sysfs_init(struct hdac_device *codec);
int hda_widget_sysfs_reinit(struct hdac_device *codec, hda_nid_t start_nid,
int num_nodes);
void hda_widget_sysfs_exit(struct hdac_device *codec);
#endif /* __HDAC_LOCAL_H */