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Diffstat (limited to 'Documentation/sound')
| -rw-r--r-- | Documentation/sound/alsa/hda_codec.txt | 322 |
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diff --git a/Documentation/sound/alsa/hda_codec.txt b/Documentation/sound/alsa/hda_codec.txt deleted file mode 100644 index de8efbc7e4bd..000000000000 --- a/Documentation/sound/alsa/hda_codec.txt +++ /dev/null @@ -1,322 +0,0 @@ -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 *); -#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 -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 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 -controller 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. - -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 hda_codec *codec; - list_for_each_entry(codec, &bus->codec_list, 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_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-management 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. - -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 - #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(). -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. -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. - - -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. - - -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 model string table -and the table with struct snd_pci_quirk 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 - -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. |