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[ALSA] hda-codec - update of documentation 

Update the documentation to reflect the last changes regarding the
power-saving mode and register caches.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>
This commit is contained in:
Takashi Iwai 2007-08-10 17:22:34 +02:00 committed by Jaroslav Kysela
parent cb53c626e1
commit 6ca2cdcc5e
1 changed files with 36 additions and 13 deletions
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49
Documentation/sound/alsa/hda_codec.txt
View File

@ -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 *);
#ifdef CONFIG_SND_HDA_POWER_SAVE
void (*pm_notify)(struct hda_codec *codec);
#endif
};
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);
#endif
#ifdef CONFIG_SND_HDA_POWER_SAVE
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
received.
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
via
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
snd_hda_resume_spdif().
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.