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      1 /*
      2  * Copyright (C) 2011 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 
     18 #ifndef ANDROID_AUDIO_HAL_INTERFACE_H
     19 #define ANDROID_AUDIO_HAL_INTERFACE_H
     20 
     21 #include <stdint.h>
     22 #include <strings.h>
     23 #include <sys/cdefs.h>
     24 #include <sys/types.h>
     25 
     26 #include <cutils/bitops.h>
     27 
     28 #include <hardware/hardware.h>
     29 #include <system/audio.h>
     30 #include <hardware/audio_effect.h>
     31 
     32 __BEGIN_DECLS
     33 
     34 /**
     35  * The id of this module
     36  */
     37 #define AUDIO_HARDWARE_MODULE_ID "audio"
     38 
     39 /**
     40  * Name of the audio devices to open
     41  */
     42 #define AUDIO_HARDWARE_INTERFACE "audio_hw_if"
     43 
     44 
     45 /* Use version 0.1 to be compatible with first generation of audio hw module with version_major
     46  * hardcoded to 1. No audio module API change.
     47  */
     48 #define AUDIO_MODULE_API_VERSION_0_1 HARDWARE_MODULE_API_VERSION(0, 1)
     49 #define AUDIO_MODULE_API_VERSION_CURRENT AUDIO_MODULE_API_VERSION_0_1
     50 
     51 /* First generation of audio devices had version hardcoded to 0. all devices with versions < 1.0
     52  * will be considered of first generation API.
     53  */
     54 #define AUDIO_DEVICE_API_VERSION_0_0 HARDWARE_DEVICE_API_VERSION(0, 0)
     55 #define AUDIO_DEVICE_API_VERSION_1_0 HARDWARE_DEVICE_API_VERSION(1, 0)
     56 #define AUDIO_DEVICE_API_VERSION_2_0 HARDWARE_DEVICE_API_VERSION(2, 0)
     57 #define AUDIO_DEVICE_API_VERSION_3_0 HARDWARE_DEVICE_API_VERSION(3, 0)
     58 #define AUDIO_DEVICE_API_VERSION_CURRENT AUDIO_DEVICE_API_VERSION_3_0
     59 /* Minimal audio HAL version supported by the audio framework */
     60 #define AUDIO_DEVICE_API_VERSION_MIN AUDIO_DEVICE_API_VERSION_2_0
     61 
     62 /**
     63  * List of known audio HAL modules. This is the base name of the audio HAL
     64  * library composed of the "audio." prefix, one of the base names below and
     65  * a suffix specific to the device.
     66  * e.g: audio.primary.goldfish.so or audio.a2dp.default.so
     67  */
     68 
     69 #define AUDIO_HARDWARE_MODULE_ID_PRIMARY "primary"
     70 #define AUDIO_HARDWARE_MODULE_ID_A2DP "a2dp"
     71 #define AUDIO_HARDWARE_MODULE_ID_USB "usb"
     72 #define AUDIO_HARDWARE_MODULE_ID_REMOTE_SUBMIX "r_submix"
     73 #define AUDIO_HARDWARE_MODULE_ID_CODEC_OFFLOAD "codec_offload"
     74 
     75 /**************************************/
     76 
     77 /**
     78  *  standard audio parameters that the HAL may need to handle
     79  */
     80 
     81 /**
     82  *  audio device parameters
     83  */
     84 
     85 /* BT SCO Noise Reduction + Echo Cancellation parameters */
     86 #define AUDIO_PARAMETER_KEY_BT_NREC "bt_headset_nrec"
     87 #define AUDIO_PARAMETER_VALUE_ON "on"
     88 #define AUDIO_PARAMETER_VALUE_OFF "off"
     89 
     90 /* TTY mode selection */
     91 #define AUDIO_PARAMETER_KEY_TTY_MODE "tty_mode"
     92 #define AUDIO_PARAMETER_VALUE_TTY_OFF "tty_off"
     93 #define AUDIO_PARAMETER_VALUE_TTY_VCO "tty_vco"
     94 #define AUDIO_PARAMETER_VALUE_TTY_HCO "tty_hco"
     95 #define AUDIO_PARAMETER_VALUE_TTY_FULL "tty_full"
     96 
     97 /* Hearing Aid Compatibility - Telecoil (HAC-T) mode on/off
     98    Strings must be in sync with CallFeaturesSetting.java */
     99 #define AUDIO_PARAMETER_KEY_HAC "HACSetting"
    100 #define AUDIO_PARAMETER_VALUE_HAC_ON "ON"
    101 #define AUDIO_PARAMETER_VALUE_HAC_OFF "OFF"
    102 
    103 /* A2DP sink address set by framework */
    104 #define AUDIO_PARAMETER_A2DP_SINK_ADDRESS "a2dp_sink_address"
    105 
    106 /* A2DP source address set by framework */
    107 #define AUDIO_PARAMETER_A2DP_SOURCE_ADDRESS "a2dp_source_address"
    108 
    109 /* Screen state */
    110 #define AUDIO_PARAMETER_KEY_SCREEN_STATE "screen_state"
    111 
    112 /* Bluetooth SCO wideband */
    113 #define AUDIO_PARAMETER_KEY_BT_SCO_WB "bt_wbs"
    114 
    115 /* Get a new HW synchronization source identifier.
    116  * Return a valid source (positive integer) or AUDIO_HW_SYNC_INVALID if an error occurs
    117  * or no HW sync is available. */
    118 #define AUDIO_PARAMETER_HW_AV_SYNC "hw_av_sync"
    119 
    120 /**
    121  *  audio stream parameters
    122  */
    123 
    124 #define AUDIO_PARAMETER_STREAM_ROUTING "routing"             /* audio_devices_t */
    125 #define AUDIO_PARAMETER_STREAM_FORMAT "format"               /* audio_format_t */
    126 #define AUDIO_PARAMETER_STREAM_CHANNELS "channels"           /* audio_channel_mask_t */
    127 #define AUDIO_PARAMETER_STREAM_FRAME_COUNT "frame_count"     /* size_t */
    128 #define AUDIO_PARAMETER_STREAM_INPUT_SOURCE "input_source"   /* audio_source_t */
    129 #define AUDIO_PARAMETER_STREAM_SAMPLING_RATE "sampling_rate" /* uint32_t */
    130 
    131 #define AUDIO_PARAMETER_DEVICE_CONNECT "connect"            /* audio_devices_t */
    132 #define AUDIO_PARAMETER_DEVICE_DISCONNECT "disconnect"      /* audio_devices_t */
    133 
    134 /* Query supported formats. The response is a '|' separated list of strings from
    135  * audio_format_t enum e.g: "sup_formats=AUDIO_FORMAT_PCM_16_BIT" */
    136 #define AUDIO_PARAMETER_STREAM_SUP_FORMATS "sup_formats"
    137 /* Query supported channel masks. The response is a '|' separated list of strings from
    138  * audio_channel_mask_t enum e.g: "sup_channels=AUDIO_CHANNEL_OUT_STEREO|AUDIO_CHANNEL_OUT_MONO" */
    139 #define AUDIO_PARAMETER_STREAM_SUP_CHANNELS "sup_channels"
    140 /* Query supported sampling rates. The response is a '|' separated list of integer values e.g:
    141  * "sup_sampling_rates=44100|48000" */
    142 #define AUDIO_PARAMETER_STREAM_SUP_SAMPLING_RATES "sup_sampling_rates"
    143 
    144 /* Set the HW synchronization source for an output stream. */
    145 #define AUDIO_PARAMETER_STREAM_HW_AV_SYNC "hw_av_sync"
    146 
    147 /* Enable mono audio playback if 1, else should be 0. */
    148 #define AUDIO_PARAMETER_MONO_OUTPUT "mono_output"
    149 
    150 /**
    151  * audio codec parameters
    152  */
    153 
    154 #define AUDIO_OFFLOAD_CODEC_PARAMS "music_offload_codec_param"
    155 #define AUDIO_OFFLOAD_CODEC_BIT_PER_SAMPLE "music_offload_bit_per_sample"
    156 #define AUDIO_OFFLOAD_CODEC_BIT_RATE "music_offload_bit_rate"
    157 #define AUDIO_OFFLOAD_CODEC_AVG_BIT_RATE "music_offload_avg_bit_rate"
    158 #define AUDIO_OFFLOAD_CODEC_ID "music_offload_codec_id"
    159 #define AUDIO_OFFLOAD_CODEC_BLOCK_ALIGN "music_offload_block_align"
    160 #define AUDIO_OFFLOAD_CODEC_SAMPLE_RATE "music_offload_sample_rate"
    161 #define AUDIO_OFFLOAD_CODEC_ENCODE_OPTION "music_offload_encode_option"
    162 #define AUDIO_OFFLOAD_CODEC_NUM_CHANNEL  "music_offload_num_channels"
    163 #define AUDIO_OFFLOAD_CODEC_DOWN_SAMPLING  "music_offload_down_sampling"
    164 #define AUDIO_OFFLOAD_CODEC_DELAY_SAMPLES  "delay_samples"
    165 #define AUDIO_OFFLOAD_CODEC_PADDING_SAMPLES  "padding_samples"
    166 
    167 /**************************************/
    168 
    169 /* common audio stream parameters and operations */
    170 struct audio_stream {
    171 
    172     /**
    173      * Return the sampling rate in Hz - eg. 44100.
    174      */
    175     uint32_t (*get_sample_rate)(const struct audio_stream *stream);
    176 
    177     /* currently unused - use set_parameters with key
    178      *    AUDIO_PARAMETER_STREAM_SAMPLING_RATE
    179      */
    180     int (*set_sample_rate)(struct audio_stream *stream, uint32_t rate);
    181 
    182     /**
    183      * Return size of input/output buffer in bytes for this stream - eg. 4800.
    184      * It should be a multiple of the frame size.  See also get_input_buffer_size.
    185      */
    186     size_t (*get_buffer_size)(const struct audio_stream *stream);
    187 
    188     /**
    189      * Return the channel mask -
    190      *  e.g. AUDIO_CHANNEL_OUT_STEREO or AUDIO_CHANNEL_IN_STEREO
    191      */
    192     audio_channel_mask_t (*get_channels)(const struct audio_stream *stream);
    193 
    194     /**
    195      * Return the audio format - e.g. AUDIO_FORMAT_PCM_16_BIT
    196      */
    197     audio_format_t (*get_format)(const struct audio_stream *stream);
    198 
    199     /* currently unused - use set_parameters with key
    200      *     AUDIO_PARAMETER_STREAM_FORMAT
    201      */
    202     int (*set_format)(struct audio_stream *stream, audio_format_t format);
    203 
    204     /**
    205      * Put the audio hardware input/output into standby mode.
    206      * Driver should exit from standby mode at the next I/O operation.
    207      * Returns 0 on success and <0 on failure.
    208      */
    209     int (*standby)(struct audio_stream *stream);
    210 
    211     /** dump the state of the audio input/output device */
    212     int (*dump)(const struct audio_stream *stream, int fd);
    213 
    214     /** Return the set of device(s) which this stream is connected to */
    215     audio_devices_t (*get_device)(const struct audio_stream *stream);
    216 
    217     /**
    218      * Currently unused - set_device() corresponds to set_parameters() with key
    219      * AUDIO_PARAMETER_STREAM_ROUTING for both input and output.
    220      * AUDIO_PARAMETER_STREAM_INPUT_SOURCE is an additional information used by
    221      * input streams only.
    222      */
    223     int (*set_device)(struct audio_stream *stream, audio_devices_t device);
    224 
    225     /**
    226      * set/get audio stream parameters. The function accepts a list of
    227      * parameter key value pairs in the form: key1=value1;key2=value2;...
    228      *
    229      * Some keys are reserved for standard parameters (See AudioParameter class)
    230      *
    231      * If the implementation does not accept a parameter change while
    232      * the output is active but the parameter is acceptable otherwise, it must
    233      * return -ENOSYS.
    234      *
    235      * The audio flinger will put the stream in standby and then change the
    236      * parameter value.
    237      */
    238     int (*set_parameters)(struct audio_stream *stream, const char *kv_pairs);
    239 
    240     /*
    241      * Returns a pointer to a heap allocated string. The caller is responsible
    242      * for freeing the memory for it using free().
    243      */
    244     char * (*get_parameters)(const struct audio_stream *stream,
    245                              const char *keys);
    246     int (*add_audio_effect)(const struct audio_stream *stream,
    247                              effect_handle_t effect);
    248     int (*remove_audio_effect)(const struct audio_stream *stream,
    249                              effect_handle_t effect);
    250 };
    251 typedef struct audio_stream audio_stream_t;
    252 
    253 /* type of asynchronous write callback events. Mutually exclusive */
    254 typedef enum {
    255     STREAM_CBK_EVENT_WRITE_READY, /* non blocking write completed */
    256     STREAM_CBK_EVENT_DRAIN_READY,  /* drain completed */
    257     STREAM_CBK_EVENT_ERROR, /* stream hit some error, let AF take action */
    258 } stream_callback_event_t;
    259 
    260 typedef int (*stream_callback_t)(stream_callback_event_t event, void *param, void *cookie);
    261 
    262 /* type of drain requested to audio_stream_out->drain(). Mutually exclusive */
    263 typedef enum {
    264     AUDIO_DRAIN_ALL,            /* drain() returns when all data has been played */
    265     AUDIO_DRAIN_EARLY_NOTIFY    /* drain() returns a short time before all data
    266                                    from the current track has been played to
    267                                    give time for gapless track switch */
    268 } audio_drain_type_t;
    269 
    270 /**
    271  * audio_stream_out is the abstraction interface for the audio output hardware.
    272  *
    273  * It provides information about various properties of the audio output
    274  * hardware driver.
    275  */
    276 
    277 struct audio_stream_out {
    278     /**
    279      * Common methods of the audio stream out.  This *must* be the first member of audio_stream_out
    280      * as users of this structure will cast a audio_stream to audio_stream_out pointer in contexts
    281      * where it's known the audio_stream references an audio_stream_out.
    282      */
    283     struct audio_stream common;
    284 
    285     /**
    286      * Return the audio hardware driver estimated latency in milliseconds.
    287      */
    288     uint32_t (*get_latency)(const struct audio_stream_out *stream);
    289 
    290     /**
    291      * Use this method in situations where audio mixing is done in the
    292      * hardware. This method serves as a direct interface with hardware,
    293      * allowing you to directly set the volume as apposed to via the framework.
    294      * This method might produce multiple PCM outputs or hardware accelerated
    295      * codecs, such as MP3 or AAC.
    296      */
    297     int (*set_volume)(struct audio_stream_out *stream, float left, float right);
    298 
    299     /**
    300      * Write audio buffer to driver. Returns number of bytes written, or a
    301      * negative status_t. If at least one frame was written successfully prior to the error,
    302      * it is suggested that the driver return that successful (short) byte count
    303      * and then return an error in the subsequent call.
    304      *
    305      * If set_callback() has previously been called to enable non-blocking mode
    306      * the write() is not allowed to block. It must write only the number of
    307      * bytes that currently fit in the driver/hardware buffer and then return
    308      * this byte count. If this is less than the requested write size the
    309      * callback function must be called when more space is available in the
    310      * driver/hardware buffer.
    311      */
    312     ssize_t (*write)(struct audio_stream_out *stream, const void* buffer,
    313                      size_t bytes);
    314 
    315     /* return the number of audio frames written by the audio dsp to DAC since
    316      * the output has exited standby
    317      */
    318     int (*get_render_position)(const struct audio_stream_out *stream,
    319                                uint32_t *dsp_frames);
    320 
    321     /**
    322      * get the local time at which the next write to the audio driver will be presented.
    323      * The units are microseconds, where the epoch is decided by the local audio HAL.
    324      */
    325     int (*get_next_write_timestamp)(const struct audio_stream_out *stream,
    326                                     int64_t *timestamp);
    327 
    328     /**
    329      * set the callback function for notifying completion of non-blocking
    330      * write and drain.
    331      * Calling this function implies that all future write() and drain()
    332      * must be non-blocking and use the callback to signal completion.
    333      */
    334     int (*set_callback)(struct audio_stream_out *stream,
    335             stream_callback_t callback, void *cookie);
    336 
    337     /**
    338      * Notifies to the audio driver to stop playback however the queued buffers are
    339      * retained by the hardware. Useful for implementing pause/resume. Empty implementation
    340      * if not supported however should be implemented for hardware with non-trivial
    341      * latency. In the pause state audio hardware could still be using power. User may
    342      * consider calling suspend after a timeout.
    343      *
    344      * Implementation of this function is mandatory for offloaded playback.
    345      */
    346     int (*pause)(struct audio_stream_out* stream);
    347 
    348     /**
    349      * Notifies to the audio driver to resume playback following a pause.
    350      * Returns error if called without matching pause.
    351      *
    352      * Implementation of this function is mandatory for offloaded playback.
    353      */
    354     int (*resume)(struct audio_stream_out* stream);
    355 
    356     /**
    357      * Requests notification when data buffered by the driver/hardware has
    358      * been played. If set_callback() has previously been called to enable
    359      * non-blocking mode, the drain() must not block, instead it should return
    360      * quickly and completion of the drain is notified through the callback.
    361      * If set_callback() has not been called, the drain() must block until
    362      * completion.
    363      * If type==AUDIO_DRAIN_ALL, the drain completes when all previously written
    364      * data has been played.
    365      * If type==AUDIO_DRAIN_EARLY_NOTIFY, the drain completes shortly before all
    366      * data for the current track has played to allow time for the framework
    367      * to perform a gapless track switch.
    368      *
    369      * Drain must return immediately on stop() and flush() call
    370      *
    371      * Implementation of this function is mandatory for offloaded playback.
    372      */
    373     int (*drain)(struct audio_stream_out* stream, audio_drain_type_t type );
    374 
    375     /**
    376      * Notifies to the audio driver to flush the queued data. Stream must already
    377      * be paused before calling flush().
    378      *
    379      * Implementation of this function is mandatory for offloaded playback.
    380      */
    381    int (*flush)(struct audio_stream_out* stream);
    382 
    383     /**
    384      * Return a recent count of the number of audio frames presented to an external observer.
    385      * This excludes frames which have been written but are still in the pipeline.
    386      * The count is not reset to zero when output enters standby.
    387      * Also returns the value of CLOCK_MONOTONIC as of this presentation count.
    388      * The returned count is expected to be 'recent',
    389      * but does not need to be the most recent possible value.
    390      * However, the associated time should correspond to whatever count is returned.
    391      * Example:  assume that N+M frames have been presented, where M is a 'small' number.
    392      * Then it is permissible to return N instead of N+M,
    393      * and the timestamp should correspond to N rather than N+M.
    394      * The terms 'recent' and 'small' are not defined.
    395      * They reflect the quality of the implementation.
    396      *
    397      * 3.0 and higher only.
    398      */
    399     int (*get_presentation_position)(const struct audio_stream_out *stream,
    400                                uint64_t *frames, struct timespec *timestamp);
    401 
    402 };
    403 typedef struct audio_stream_out audio_stream_out_t;
    404 
    405 struct audio_stream_in {
    406     /**
    407      * Common methods of the audio stream in.  This *must* be the first member of audio_stream_in
    408      * as users of this structure will cast a audio_stream to audio_stream_in pointer in contexts
    409      * where it's known the audio_stream references an audio_stream_in.
    410      */
    411     struct audio_stream common;
    412 
    413     /** set the input gain for the audio driver. This method is for
    414      *  for future use */
    415     int (*set_gain)(struct audio_stream_in *stream, float gain);
    416 
    417     /** Read audio buffer in from audio driver. Returns number of bytes read, or a
    418      *  negative status_t. If at least one frame was read prior to the error,
    419      *  read should return that byte count and then return an error in the subsequent call.
    420      */
    421     ssize_t (*read)(struct audio_stream_in *stream, void* buffer,
    422                     size_t bytes);
    423 
    424     /**
    425      * Return the amount of input frames lost in the audio driver since the
    426      * last call of this function.
    427      * Audio driver is expected to reset the value to 0 and restart counting
    428      * upon returning the current value by this function call.
    429      * Such loss typically occurs when the user space process is blocked
    430      * longer than the capacity of audio driver buffers.
    431      *
    432      * Unit: the number of input audio frames
    433      */
    434     uint32_t (*get_input_frames_lost)(struct audio_stream_in *stream);
    435 
    436     /**
    437      * Return a recent count of the number of audio frames received and
    438      * the clock time associated with that frame count.
    439      *
    440      * frames is the total frame count received. This should be as early in
    441      *     the capture pipeline as possible. In general,
    442      *     frames should be non-negative and should not go "backwards".
    443      *
    444      * time is the clock MONOTONIC time when frames was measured. In general,
    445      *     time should be a positive quantity and should not go "backwards".
    446      *
    447      * The status returned is 0 on success, -ENOSYS if the device is not
    448      * ready/available, or -EINVAL if the arguments are null or otherwise invalid.
    449      */
    450     int (*get_capture_position)(const struct audio_stream_in *stream,
    451                                 int64_t *frames, int64_t *time);
    452 };
    453 typedef struct audio_stream_in audio_stream_in_t;
    454 
    455 /**
    456  * return the frame size (number of bytes per sample).
    457  *
    458  * Deprecated: use audio_stream_out_frame_size() or audio_stream_in_frame_size() instead.
    459  */
    460 __attribute__((__deprecated__))
    461 static inline size_t audio_stream_frame_size(const struct audio_stream *s)
    462 {
    463     size_t chan_samp_sz;
    464     audio_format_t format = s->get_format(s);
    465 
    466     if (audio_has_proportional_frames(format)) {
    467         chan_samp_sz = audio_bytes_per_sample(format);
    468         return popcount(s->get_channels(s)) * chan_samp_sz;
    469     }
    470 
    471     return sizeof(int8_t);
    472 }
    473 
    474 /**
    475  * return the frame size (number of bytes per sample) of an output stream.
    476  */
    477 static inline size_t audio_stream_out_frame_size(const struct audio_stream_out *s)
    478 {
    479     size_t chan_samp_sz;
    480     audio_format_t format = s->common.get_format(&s->common);
    481 
    482     if (audio_has_proportional_frames(format)) {
    483         chan_samp_sz = audio_bytes_per_sample(format);
    484         return audio_channel_count_from_out_mask(s->common.get_channels(&s->common)) * chan_samp_sz;
    485     }
    486 
    487     return sizeof(int8_t);
    488 }
    489 
    490 /**
    491  * return the frame size (number of bytes per sample) of an input stream.
    492  */
    493 static inline size_t audio_stream_in_frame_size(const struct audio_stream_in *s)
    494 {
    495     size_t chan_samp_sz;
    496     audio_format_t format = s->common.get_format(&s->common);
    497 
    498     if (audio_has_proportional_frames(format)) {
    499         chan_samp_sz = audio_bytes_per_sample(format);
    500         return audio_channel_count_from_in_mask(s->common.get_channels(&s->common)) * chan_samp_sz;
    501     }
    502 
    503     return sizeof(int8_t);
    504 }
    505 
    506 /**********************************************************************/
    507 
    508 /**
    509  * Every hardware module must have a data structure named HAL_MODULE_INFO_SYM
    510  * and the fields of this data structure must begin with hw_module_t
    511  * followed by module specific information.
    512  */
    513 struct audio_module {
    514     struct hw_module_t common;
    515 };
    516 
    517 struct audio_hw_device {
    518     /**
    519      * Common methods of the audio device.  This *must* be the first member of audio_hw_device
    520      * as users of this structure will cast a hw_device_t to audio_hw_device pointer in contexts
    521      * where it's known the hw_device_t references an audio_hw_device.
    522      */
    523     struct hw_device_t common;
    524 
    525     /**
    526      * used by audio flinger to enumerate what devices are supported by
    527      * each audio_hw_device implementation.
    528      *
    529      * Return value is a bitmask of 1 or more values of audio_devices_t
    530      *
    531      * NOTE: audio HAL implementations starting with
    532      * AUDIO_DEVICE_API_VERSION_2_0 do not implement this function.
    533      * All supported devices should be listed in audio_policy.conf
    534      * file and the audio policy manager must choose the appropriate
    535      * audio module based on information in this file.
    536      */
    537     uint32_t (*get_supported_devices)(const struct audio_hw_device *dev);
    538 
    539     /**
    540      * check to see if the audio hardware interface has been initialized.
    541      * returns 0 on success, -ENODEV on failure.
    542      */
    543     int (*init_check)(const struct audio_hw_device *dev);
    544 
    545     /** set the audio volume of a voice call. Range is between 0.0 and 1.0 */
    546     int (*set_voice_volume)(struct audio_hw_device *dev, float volume);
    547 
    548     /**
    549      * set the audio volume for all audio activities other than voice call.
    550      * Range between 0.0 and 1.0. If any value other than 0 is returned,
    551      * the software mixer will emulate this capability.
    552      */
    553     int (*set_master_volume)(struct audio_hw_device *dev, float volume);
    554 
    555     /**
    556      * Get the current master volume value for the HAL, if the HAL supports
    557      * master volume control.  AudioFlinger will query this value from the
    558      * primary audio HAL when the service starts and use the value for setting
    559      * the initial master volume across all HALs.  HALs which do not support
    560      * this method may leave it set to NULL.
    561      */
    562     int (*get_master_volume)(struct audio_hw_device *dev, float *volume);
    563 
    564     /**
    565      * set_mode is called when the audio mode changes. AUDIO_MODE_NORMAL mode
    566      * is for standard audio playback, AUDIO_MODE_RINGTONE when a ringtone is
    567      * playing, and AUDIO_MODE_IN_CALL when a call is in progress.
    568      */
    569     int (*set_mode)(struct audio_hw_device *dev, audio_mode_t mode);
    570 
    571     /* mic mute */
    572     int (*set_mic_mute)(struct audio_hw_device *dev, bool state);
    573     int (*get_mic_mute)(const struct audio_hw_device *dev, bool *state);
    574 
    575     /* set/get global audio parameters */
    576     int (*set_parameters)(struct audio_hw_device *dev, const char *kv_pairs);
    577 
    578     /*
    579      * Returns a pointer to a heap allocated string. The caller is responsible
    580      * for freeing the memory for it using free().
    581      */
    582     char * (*get_parameters)(const struct audio_hw_device *dev,
    583                              const char *keys);
    584 
    585     /* Returns audio input buffer size according to parameters passed or
    586      * 0 if one of the parameters is not supported.
    587      * See also get_buffer_size which is for a particular stream.
    588      */
    589     size_t (*get_input_buffer_size)(const struct audio_hw_device *dev,
    590                                     const struct audio_config *config);
    591 
    592     /** This method creates and opens the audio hardware output stream.
    593      * The "address" parameter qualifies the "devices" audio device type if needed.
    594      * The format format depends on the device type:
    595      * - Bluetooth devices use the MAC address of the device in the form "00:11:22:AA:BB:CC"
    596      * - USB devices use the ALSA card and device numbers in the form  "card=X;device=Y"
    597      * - Other devices may use a number or any other string.
    598      */
    599 
    600     int (*open_output_stream)(struct audio_hw_device *dev,
    601                               audio_io_handle_t handle,
    602                               audio_devices_t devices,
    603                               audio_output_flags_t flags,
    604                               struct audio_config *config,
    605                               struct audio_stream_out **stream_out,
    606                               const char *address);
    607 
    608     void (*close_output_stream)(struct audio_hw_device *dev,
    609                                 struct audio_stream_out* stream_out);
    610 
    611     /** This method creates and opens the audio hardware input stream */
    612     int (*open_input_stream)(struct audio_hw_device *dev,
    613                              audio_io_handle_t handle,
    614                              audio_devices_t devices,
    615                              struct audio_config *config,
    616                              struct audio_stream_in **stream_in,
    617                              audio_input_flags_t flags,
    618                              const char *address,
    619                              audio_source_t source);
    620 
    621     void (*close_input_stream)(struct audio_hw_device *dev,
    622                                struct audio_stream_in *stream_in);
    623 
    624     /** This method dumps the state of the audio hardware */
    625     int (*dump)(const struct audio_hw_device *dev, int fd);
    626 
    627     /**
    628      * set the audio mute status for all audio activities.  If any value other
    629      * than 0 is returned, the software mixer will emulate this capability.
    630      */
    631     int (*set_master_mute)(struct audio_hw_device *dev, bool mute);
    632 
    633     /**
    634      * Get the current master mute status for the HAL, if the HAL supports
    635      * master mute control.  AudioFlinger will query this value from the primary
    636      * audio HAL when the service starts and use the value for setting the
    637      * initial master mute across all HALs.  HALs which do not support this
    638      * method may leave it set to NULL.
    639      */
    640     int (*get_master_mute)(struct audio_hw_device *dev, bool *mute);
    641 
    642     /**
    643      * Routing control
    644      */
    645 
    646     /* Creates an audio patch between several source and sink ports.
    647      * The handle is allocated by the HAL and should be unique for this
    648      * audio HAL module. */
    649     int (*create_audio_patch)(struct audio_hw_device *dev,
    650                                unsigned int num_sources,
    651                                const struct audio_port_config *sources,
    652                                unsigned int num_sinks,
    653                                const struct audio_port_config *sinks,
    654                                audio_patch_handle_t *handle);
    655 
    656     /* Release an audio patch */
    657     int (*release_audio_patch)(struct audio_hw_device *dev,
    658                                audio_patch_handle_t handle);
    659 
    660     /* Fills the list of supported attributes for a given audio port.
    661      * As input, "port" contains the information (type, role, address etc...)
    662      * needed by the HAL to identify the port.
    663      * As output, "port" contains possible attributes (sampling rates, formats,
    664      * channel masks, gain controllers...) for this port.
    665      */
    666     int (*get_audio_port)(struct audio_hw_device *dev,
    667                           struct audio_port *port);
    668 
    669     /* Set audio port configuration */
    670     int (*set_audio_port_config)(struct audio_hw_device *dev,
    671                          const struct audio_port_config *config);
    672 
    673 };
    674 typedef struct audio_hw_device audio_hw_device_t;
    675 
    676 /** convenience API for opening and closing a supported device */
    677 
    678 static inline int audio_hw_device_open(const struct hw_module_t* module,
    679                                        struct audio_hw_device** device)
    680 {
    681     return module->methods->open(module, AUDIO_HARDWARE_INTERFACE,
    682                                  (struct hw_device_t**)device);
    683 }
    684 
    685 static inline int audio_hw_device_close(struct audio_hw_device* device)
    686 {
    687     return device->common.close(&device->common);
    688 }
    689 
    690 
    691 __END_DECLS
    692 
    693 #endif  // ANDROID_AUDIO_INTERFACE_H
    694