300 lines
10 KiB
Plaintext
300 lines
10 KiB
Plaintext
Notes on Universal Interface for Intel High Definition Audio Codec
|
|
------------------------------------------------------------------
|
|
|
|
Takashi Iwai <tiwai@suse.de>
|
|
|
|
|
|
[Still a draft version]
|
|
|
|
|
|
General
|
|
=======
|
|
|
|
The snd-hda-codec module supports the generic access function for the
|
|
High Definition (HD) audio codecs. It's designed to be independent
|
|
from the controller code like ac97 codec module. The real accessors
|
|
from/to the controller must be implemented in the lowlevel driver.
|
|
|
|
The structure of this module is similar with ac97_codec module.
|
|
Each codec chip belongs to a bus class which communicates with the
|
|
controller.
|
|
|
|
|
|
Initialization of Bus Instance
|
|
==============================
|
|
|
|
The card driver has to create struct hda_bus at first. The template
|
|
struct should be filled and passed to the constructor:
|
|
|
|
struct hda_bus_template {
|
|
void *private_data;
|
|
struct pci_dev *pci;
|
|
const char *modelname;
|
|
struct hda_bus_ops ops;
|
|
};
|
|
|
|
The card driver can set and use the private_data field to retrieve its
|
|
own data in callback functions. The pci field is used when the patch
|
|
needs to check the PCI subsystem IDs, so on. For non-PCI system, it
|
|
doesn't have to be set, of course.
|
|
The modelname field specifies the board's specific configuration. The
|
|
string is passed to the codec parser, and it depends on the parser how
|
|
the string is used.
|
|
These fields, private_data, pci and modelname are all optional.
|
|
|
|
The ops field contains the callback functions as the following:
|
|
|
|
struct hda_bus_ops {
|
|
int (*command)(struct hda_codec *codec, hda_nid_t nid, int direct,
|
|
unsigned int verb, unsigned int parm);
|
|
unsigned int (*get_response)(struct hda_codec *codec);
|
|
void (*private_free)(struct hda_bus *);
|
|
};
|
|
|
|
The command callback is called when the codec module needs to send a
|
|
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
|
|
destructor to release any necessary data in the lowlevel driver.
|
|
|
|
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.
|
|
|
|
int snd_hda_bus_new(struct snd_card *card, const struct hda_bus_template *temp,
|
|
struct hda_bus **busp);
|
|
|
|
It returns zero if successful. A negative return value means any
|
|
error during creation.
|
|
|
|
|
|
Creation of Codec Instance
|
|
==========================
|
|
|
|
Each codec chip on the board is then created on the BUS instance.
|
|
To create a codec instance, call snd_hda_codec_new().
|
|
|
|
int snd_hda_codec_new(struct hda_bus *bus, unsigned int codec_addr,
|
|
struct hda_codec **codecp);
|
|
|
|
The first argument is the BUS instance, the second argument is the
|
|
address of the codec, and the last one is the pointer to store the
|
|
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);
|
|
...
|
|
}
|
|
|
|
The codec isn't initialized at this stage properly. The
|
|
initialization sequence is called when the controls are built later.
|
|
|
|
|
|
Codec Access
|
|
============
|
|
|
|
To access codec, use snd_codec_read() and snd_codec_write().
|
|
snd_hda_param_read() is for reading parameters.
|
|
For writing a sequence of verbs, use snd_hda_sequence_write().
|
|
|
|
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.
|
|
|
|
When an unsolicited event happens, pass the event via
|
|
snd_hda_queue_unsol_event() so that the codec routines will process it
|
|
later.
|
|
|
|
|
|
(Mixer) Controls
|
|
================
|
|
|
|
To create mixer controls of all codecs, call
|
|
snd_hda_build_controls(). It then builds the mixers and does
|
|
initialization stuff on each codec.
|
|
|
|
|
|
PCM Stuff
|
|
=========
|
|
|
|
snd_hda_build_pcms() gives the necessary information to create PCM
|
|
streams. When it's called, each codec belonging to the bus stores
|
|
codec->num_pcms and codec->pcm_info fields. The num_pcms indicates
|
|
the number of elements in pcm_info array. The card driver is supposed
|
|
to traverse the codec linked list, read the pcm information in
|
|
pcm_info array, and build pcm instances according to them.
|
|
|
|
The pcm_info array contains the following record:
|
|
|
|
/* PCM information for each substream */
|
|
struct hda_pcm_stream {
|
|
unsigned int substreams; /* number of substreams, 0 = not exist */
|
|
unsigned int channels_min; /* min. number of channels */
|
|
unsigned int channels_max; /* max. number of channels */
|
|
hda_nid_t nid; /* default NID to query rates/formats/bps, or set up */
|
|
u32 rates; /* supported rates */
|
|
u64 formats; /* supported formats (SNDRV_PCM_FMTBIT_) */
|
|
unsigned int maxbps; /* supported max. bit per sample */
|
|
struct hda_pcm_ops ops;
|
|
};
|
|
|
|
/* for PCM creation */
|
|
struct hda_pcm {
|
|
char *name;
|
|
struct hda_pcm_stream stream[2];
|
|
};
|
|
|
|
The name can be passed to snd_pcm_new(). The stream field contains
|
|
the information for playback (SNDRV_PCM_STREAM_PLAYBACK = 0) and
|
|
capture (SNDRV_PCM_STREAM_CAPTURE = 1) directions. The card driver
|
|
should pass substreams to snd_pcm_new() for the number of substreams
|
|
to create.
|
|
|
|
The channels_min, channels_max, rates and formats should be copied to
|
|
runtime->hw record. They and maxbps fields are used also to compute
|
|
the format value for the HDA codec and controller. Call
|
|
snd_hda_calc_stream_format() to get the format value.
|
|
|
|
The ops field contains the following callback functions:
|
|
|
|
struct hda_pcm_ops {
|
|
int (*open)(struct hda_pcm_stream *info, struct hda_codec *codec,
|
|
struct snd_pcm_substream *substream);
|
|
int (*close)(struct hda_pcm_stream *info, struct hda_codec *codec,
|
|
struct snd_pcm_substream *substream);
|
|
int (*prepare)(struct hda_pcm_stream *info, struct hda_codec *codec,
|
|
unsigned int stream_tag, unsigned int format,
|
|
struct snd_pcm_substream *substream);
|
|
int (*cleanup)(struct hda_pcm_stream *info, struct hda_codec *codec,
|
|
struct snd_pcm_substream *substream);
|
|
};
|
|
|
|
All are non-NULL, so you can call them safely without NULL check.
|
|
|
|
The open callback should be called in PCM open after runtime->hw is
|
|
set up. It may override some setting and constraints additionally.
|
|
Similarly, the close callback should be called in the PCM close.
|
|
|
|
The prepare callback should be called in PCM prepare. This will set
|
|
up the codec chip properly for the operation. The cleanup should be
|
|
called in hw_free to clean up the configuration.
|
|
|
|
The caller should check the return value, at least for open and
|
|
prepare callbacks. When a negative value is returned, some error
|
|
occurred.
|
|
|
|
|
|
Proc Files
|
|
==========
|
|
|
|
Each codec dumps the widget node information in
|
|
/proc/asound/card*/codec#* file. This information would be really
|
|
helpful for debugging. Please provide its contents together with the
|
|
bug report.
|
|
|
|
|
|
Power Management
|
|
================
|
|
|
|
It's simple:
|
|
Call snd_hda_suspend() in the PM suspend callback.
|
|
Call snd_hda_resume() in the PM resume callback.
|
|
|
|
|
|
Codec Preset (Patch)
|
|
====================
|
|
|
|
To set up and handle the codec functionality fully, each codec may
|
|
have a codec preset (patch). It's defined in struct hda_codec_preset:
|
|
|
|
struct hda_codec_preset {
|
|
unsigned int id;
|
|
unsigned int mask;
|
|
unsigned int subs;
|
|
unsigned int subs_mask;
|
|
unsigned int rev;
|
|
const char *name;
|
|
int (*patch)(struct hda_codec *codec);
|
|
};
|
|
|
|
When the codec id and codec subsystem id match with the given id and
|
|
subs fields bitwise (with bitmask mask and subs_mask), the callback
|
|
patch is called. The patch callback should initialize the codec and
|
|
set the codec->patch_ops field. This is defined as below:
|
|
|
|
struct hda_codec_ops {
|
|
int (*build_controls)(struct hda_codec *codec);
|
|
int (*build_pcms)(struct hda_codec *codec);
|
|
int (*init)(struct hda_codec *codec);
|
|
void (*free)(struct hda_codec *codec);
|
|
void (*unsol_event)(struct hda_codec *codec, unsigned int res);
|
|
#ifdef CONFIG_PM
|
|
int (*suspend)(struct hda_codec *codec, pm_message_t state);
|
|
int (*resume)(struct hda_codec *codec);
|
|
#endif
|
|
};
|
|
|
|
The build_controls callback is called from snd_hda_build_controls().
|
|
Similarly, the build_pcms callback is called from
|
|
snd_hda_build_pcms(). The init callback is called after
|
|
build_controls to initialize the hardware.
|
|
The free callback is called as a destructor.
|
|
|
|
The unsol_event callback is called when an unsolicited event is
|
|
received.
|
|
|
|
The suspend and resume callbacks are for power management.
|
|
|
|
Each entry can be NULL if not necessary to be called.
|
|
|
|
|
|
Generic Parser
|
|
==============
|
|
|
|
When the device doesn't match with any given presets, the widgets are
|
|
parsed via th generic parser (hda_generic.c). Its support is
|
|
limited: no multi-channel support, for example.
|
|
|
|
|
|
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().
|
|
|
|
|
|
Helper Functions
|
|
================
|
|
|
|
snd_hda_get_codec_name() stores the codec name on the given string.
|
|
|
|
snd_hda_check_board_config() can be used to obtain the configuration
|
|
information matching with the device. Define the table with struct
|
|
hda_board_config entries (zero-terminated), and pass it to the
|
|
function. The function checks the modelname given 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.
|
|
|
|
Macros HDA_CODEC_VOLUME(), HDA_CODEC_MUTE() and their variables can be
|
|
used for the entry of struct snd_kcontrol_new.
|
|
|
|
The input MUX helper callbacks for such a control are provided, too:
|
|
snd_hda_input_mux_info() and snd_hda_input_mux_put(). See
|
|
patch_realtek.c for example.
|