path: root/Documentation/sound/alsa/hda_codec.txt
diff options
Diffstat (limited to 'Documentation/sound/alsa/hda_codec.txt')
1 files changed, 36 insertions, 13 deletions
diff --git a/Documentation/sound/alsa/hda_codec.txt b/Documentation/sound/alsa/hda_codec.txt
index 4eaae2a45534..8e1b02526698 100644
--- a/Documentation/sound/alsa/hda_codec.txt
+++ b/Documentation/sound/alsa/hda_codec.txt
@@ -49,6 +49,9 @@ struct hda_bus_ops {
unsigned int verb, unsigned int parm);
unsigned int (*get_response)(struct hda_codec *codec);
void (*private_free)(struct hda_bus *);
+ void (*pm_notify)(struct hda_codec *codec);
The command callback is called when the codec module needs to send a
@@ -56,9 +59,16 @@ VERB to the controller. It's always a single command.
The get_response callback is called when the codec requires the answer
for the last command. These two callbacks are mandatory and have to
be given.
-The last, private_free callback, is optional. It's called in the
+The third, private_free callback, is optional. It's called in the
destructor to release any necessary data in the lowlevel driver.
+The pm_notify callback is available only with
+CONFIG_SND_HDA_POWER_SAVE kconfig. It's called when the codec needs
+to power up or may power down. The controller should check the all
+belonging codecs on the bus whether they are actually powered off
+(check codec->power_on), and optionally the driver may power down the
+contoller side, too.
The bus instance is created via snd_hda_bus_new(). You need to pass
the card instance, the template, and the pointer to store the
resultant bus instance.
@@ -86,10 +96,8 @@ resultant codec instance (can be NULL if not needed).
The codec is stored in a linked list of bus instance. You can follow
the codec list like:
- struct list_head *p;
struct hda_codec *codec;
- list_for_each(p, &bus->codec_list) {
- codec = list_entry(p, struct hda_codec, list);
+ list_for_each_entry(codec, &bus->codec_list, list) {
@@ -100,10 +108,15 @@ initialization sequence is called when the controls are built later.
Codec Access
-To access codec, use snd_codec_read() and snd_codec_write().
+To access codec, use snd_hda_codec_read() and snd_hda_codec_write().
snd_hda_param_read() is for reading parameters.
For writing a sequence of verbs, use snd_hda_sequence_write().
+There are variants of cached read/write, snd_hda_codec_write_cache(),
+snd_hda_sequence_write_cache(). These are used for recording the
+register states for the power-mangement resume. When no PM is needed,
+these are equivalent with non-cached version.
To retrieve the number of sub nodes connected to the given node, use
snd_hda_get_sub_nodes(). The connection list can be obtained via
snd_hda_get_connections() call.
@@ -239,6 +252,10 @@ set the codec->patch_ops field. This is defined as below:
int (*suspend)(struct hda_codec *codec, pm_message_t state);
int (*resume)(struct hda_codec *codec);
+ int (*check_power_status)(struct hda_codec *codec,
+ hda_nid_t nid);
+ #endif
The build_controls callback is called from snd_hda_build_controls().
@@ -251,6 +268,18 @@ The unsol_event callback is called when an unsolicited event is
The suspend and resume callbacks are for power management.
+They can be NULL if no special sequence is required. When the resume
+callback is NULL, the driver calls the init callback and resumes the
+registers from the cache. If other handling is needed, you'd need to
+write your own resume callback. There, the amp values can be resumed
+ void snd_hda_codec_resume_amp(struct hda_codec *codec);
+and the other codec registers via
+ void snd_hda_codec_resume_cache(struct hda_codec *codec);
+The check_power_status callback is called when the amp value of the
+given widget NID is changed. The codec code can turn on/off the power
+appropriately from this information.
Each entry can be NULL if not necessary to be called.
@@ -267,8 +296,7 @@ Digital I/O
Call snd_hda_create_spdif_out_ctls() from the patch to create controls
-related with SPDIF out. In the patch resume callback, call
+related with SPDIF out.
Helper Functions
@@ -284,12 +312,7 @@ as a module parameter, and PCI subsystem IDs. If the matching entry
is found, it returns the config field value.
snd_hda_add_new_ctls() can be used to create and add control entries.
-Pass the zero-terminated array of struct snd_kcontrol_new. The same array
-can be passed to snd_hda_resume_ctls() for resume.
-Note that this will call control->put callback of these entries. So,
-put callback should check codec->in_resume and force to restore the
-given value if it's non-zero even if the value is identical with the
-cached value.
+Pass the zero-terminated array of struct snd_kcontrol_new
Macros HDA_CODEC_VOLUME(), HDA_CODEC_MUTE() and their variables can be
used for the entry of struct snd_kcontrol_new.