include/xen/interface/io/sndif.h

   1 /******************************************************************************
   2  * sndif.h
   3  *
   4  * Unified sound-device I/O interface for Xen guest OSes.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to
   8  * deal in the Software without restriction, including without limitation the
   9  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
  10  * sell copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  21  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  22  * DEALINGS IN THE SOFTWARE.
  23  *
  24  * Copyright (C) 2013-2015 GlobalLogic Inc.
  25  * Copyright (C) 2016-2017 EPAM Systems Inc.
  26  *
  27  * Authors: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
  28  *          Oleksandr Grytsov <oleksandr_grytsov@epam.com>
  29  *          Oleksandr Dmytryshyn <oleksandr.dmytryshyn@globallogic.com>
  30  *          Iurii Konovalenko <iurii.konovalenko@globallogic.com>
  31  */
  32
  33 #ifndef __XEN_PUBLIC_IO_SNDIF_H__
  34 #define __XEN_PUBLIC_IO_SNDIF_H__
  35
  36 #include "ring.h"
  37 #include "../grant_table.h"
  38
  39 /*
  40  ******************************************************************************
  41  *                  Feature and Parameter Negotiation
  42  ******************************************************************************
  43  *
  44  * Front->back notifications: when enqueuing a new request, sending a
  45  * notification can be made conditional on xensnd_req (i.e., the generic
  46  * hold-off mechanism provided by the ring macros). Backends must set
  47  * xensnd_req appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
  48  *
  49  * Back->front notifications: when enqueuing a new response, sending a
  50  * notification can be made conditional on xensnd_resp (i.e., the generic
  51  * hold-off mechanism provided by the ring macros). Frontends must set
  52  * xensnd_resp appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
  53  *
  54  * The two halves of a para-virtual sound card driver utilize nodes within
  55  * XenStore to communicate capabilities and to negotiate operating parameters.
  56  * This section enumerates these nodes which reside in the respective front and
  57  * backend portions of XenStore, following the XenBus convention.
  58  *
  59  * All data in XenStore is stored as strings. Nodes specifying numeric
  60  * values are encoded in decimal. Integer value ranges listed below are
  61  * expressed as fixed sized integer types capable of storing the conversion
  62  * of a properly formated node string, without loss of information.
  63  *
  64  ******************************************************************************
  65  *                        Example configuration
  66  ******************************************************************************
  67  *
  68  * Note: depending on the use-case backend can expose more sound cards and
  69  * PCM devices/streams than the underlying HW physically has by employing
  70  * SW mixers, configuring virtual sound streams, channels etc.
  71  *
  72  * This is an example of backend and frontend configuration:
  73  *
  74  *--------------------------------- Backend -----------------------------------
  75  *
  76  * /local/domain/0/backend/vsnd/1/0/frontend-id = "1"
  77  * /local/domain/0/backend/vsnd/1/0/frontend = "/local/domain/1/device/vsnd/0"
  78  * /local/domain/0/backend/vsnd/1/0/state = "4"
  79  * /local/domain/0/backend/vsnd/1/0/versions = "1,2"
  80  *
  81  *--------------------------------- Frontend ----------------------------------
  82  *
  83  * /local/domain/1/device/vsnd/0/backend-id = "0"
  84  * /local/domain/1/device/vsnd/0/backend = "/local/domain/0/backend/vsnd/1/0"
  85  * /local/domain/1/device/vsnd/0/state = "4"
  86  * /local/domain/1/device/vsnd/0/version = "1"
  87  *
  88  *----------------------------- Card configuration ----------------------------
  89  *
  90  * /local/domain/1/device/vsnd/0/short-name = "Card short name"
  91  * /local/domain/1/device/vsnd/0/long-name = "Card long name"
  92  * /local/domain/1/device/vsnd/0/sample-rates = "8000,32000,44100,48000,96000"
  93  * /local/domain/1/device/vsnd/0/sample-formats = "s8,u8,s16_le,s16_be"
  94  * /local/domain/1/device/vsnd/0/buffer-size = "262144"
  95  *
  96  *------------------------------- PCM device 0 --------------------------------
  97  *
  98  * /local/domain/1/device/vsnd/0/0/name = "General analog"
  99  * /local/domain/1/device/vsnd/0/0/channels-max = "5"
 100  *
 101  *----------------------------- Stream 0, playback ----------------------------
 102  *
 103  * /local/domain/1/device/vsnd/0/0/0/type = "p"
 104  * /local/domain/1/device/vsnd/0/0/0/sample-formats = "s8,u8"
 105  * /local/domain/1/device/vsnd/0/0/0/unique-id = "0"
 106  *
 107  * /local/domain/1/device/vsnd/0/0/0/ring-ref = "386"
 108  * /local/domain/1/device/vsnd/0/0/0/event-channel = "15"
 109  *
 110  *------------------------------ Stream 1, capture ----------------------------
 111  *
 112  * /local/domain/1/device/vsnd/0/0/1/type = "c"
 113  * /local/domain/1/device/vsnd/0/0/1/channels-max = "2"
 114  * /local/domain/1/device/vsnd/0/0/1/unique-id = "1"
 115  *
 116  * /local/domain/1/device/vsnd/0/0/1/ring-ref = "384"
 117  * /local/domain/1/device/vsnd/0/0/1/event-channel = "13"
 118  *
 119  *------------------------------- PCM device 1 --------------------------------
 120  *
 121  * /local/domain/1/device/vsnd/0/1/name = "HDMI-0"
 122  * /local/domain/1/device/vsnd/0/1/sample-rates = "8000,32000,44100"
 123  *
 124  *------------------------------ Stream 0, capture ----------------------------
 125  *
 126  * /local/domain/1/device/vsnd/0/1/0/type = "c"
 127  * /local/domain/1/device/vsnd/0/1/0/unique-id = "2"
 128  *
 129  * /local/domain/1/device/vsnd/0/1/0/ring-ref = "387"
 130  * /local/domain/1/device/vsnd/0/1/0/event-channel = "151"
 131  *
 132  *------------------------------- PCM device 2 --------------------------------
 133  *
 134  * /local/domain/1/device/vsnd/0/2/name = "SPDIF"
 135  *
 136  *----------------------------- Stream 0, playback ----------------------------
 137  *
 138  * /local/domain/1/device/vsnd/0/2/0/type = "p"
 139  * /local/domain/1/device/vsnd/0/2/0/unique-id = "3"
 140  *
 141  * /local/domain/1/device/vsnd/0/2/0/ring-ref = "389"
 142  * /local/domain/1/device/vsnd/0/2/0/event-channel = "152"
 143  *
 144  ******************************************************************************
 145  *                            Backend XenBus Nodes
 146  ******************************************************************************
 147  *
 148  *----------------------------- Protocol version ------------------------------
 149  *
 150  * versions
 151  *      Values:         <string>
 152  *
 153  *      List of XENSND_LIST_SEPARATOR separated protocol versions supported
 154  *      by the backend. For example "1,2,3".
 155  *
 156  ******************************************************************************
 157  *                            Frontend XenBus Nodes
 158  ******************************************************************************
 159  *
 160  *-------------------------------- Addressing ---------------------------------
 161  *
 162  * dom-id
 163  *      Values:         <uint16_t>
 164  *
 165  *      Domain identifier.
 166  *
 167  * dev-id
 168  *      Values:         <uint16_t>
 169  *
 170  *      Device identifier.
 171  *
 172  * pcm-dev-idx
 173  *      Values:         <uint8_t>
 174  *
 175  *      Zero based contigous index of the PCM device.
 176  *
 177  * stream-idx
 178  *      Values:         <uint8_t>
 179  *
 180  *      Zero based contigous index of the stream of the PCM device.
 181  *
 182  * The following pattern is used for addressing:
 183  *   /local/domain/<dom-id>/device/vsnd/<dev-id>/<pcm-dev-idx>/<stream-idx>/...
 184  *
 185  *----------------------------- Protocol version ------------------------------
 186  *
 187  * version
 188  *      Values:         <string>
 189  *
 190  *      Protocol version, chosen among the ones supported by the backend.
 191  *
 192  *------------------------------- PCM settings --------------------------------
 193  *
 194  * Every virtualized sound frontend has a set of PCM devices and streams, each
 195  * could be individually configured. Part of the PCM configuration can be
 196  * defined at higher level of the hierarchy and be fully or partially re-used
 197  * by the underlying layers. These configuration values are:
 198  *  o number of channels (min/max)
 199  *  o supported sample rates
 200  *  o supported sample formats.
 201  * E.g. one can define these values for the whole card, device or stream.
 202  * Every underlying layer in turn can re-define some or all of them to better
 203  * fit its needs. For example, card may define number of channels to be
 204  * in [1; 8] range, and some particular stream may be limited to [1; 2] only.
 205  * The rule is that the underlying layer must be a subset of the upper layer
 206  * range.
 207  *
 208  * channels-min
 209  *      Values:         <uint8_t>
 210  *
 211  *      The minimum amount of channels that is supported, [1; channels-max].
 212  *      Optional, if not set or omitted a value of 1 is used.
 213  *
 214  * channels-max
 215  *      Values:         <uint8_t>
 216  *
 217  *      The maximum amount of channels that is supported.
 218  *      Must be at least <channels-min>.
 219  *
 220  * sample-rates
 221  *      Values:         <list of uint32_t>
 222  *
 223  *      List of supported sample rates separated by XENSND_LIST_SEPARATOR.
 224  *      Sample rates are expressed as a list of decimal values w/o any
 225  *      ordering requirement.
 226  *
 227  * sample-formats
 228  *      Values:         <list of XENSND_PCM_FORMAT_XXX_STR>
 229  *
 230  *      List of supported sample formats separated by XENSND_LIST_SEPARATOR.
 231  *      Items must not exceed XENSND_SAMPLE_FORMAT_MAX_LEN length.
 232  *
 233  * buffer-size
 234  *      Values:         <uint32_t>
 235  *
 236  *      The maximum size in octets of the buffer to allocate per stream.
 237  *
 238  *----------------------- Virtual sound card settings -------------------------
 239  * short-name
 240  *      Values:         <char[32]>
 241  *
 242  *      Short name of the virtual sound card. Optional.
 243  *
 244  * long-name
 245  *      Values:         <char[80]>
 246  *
 247  *      Long name of the virtual sound card. Optional.
 248  *
 249  *----------------------------- Device settings -------------------------------
 250  * name
 251  *      Values:         <char[80]>
 252  *
 253  *      Name of the sound device within the virtual sound card. Optional.
 254  *
 255  *----------------------------- Stream settings -------------------------------
 256  *
 257  * type
 258  *      Values:         "p", "c"
 259  *
 260  *      Stream type: "p" - playback stream, "c" - capture stream
 261  *
 262  *      If both capture and playback are needed then two streams need to be
 263  *      defined under the same device.
 264  *
 265  * unique-id
 266  *      Values:         <uint32_t>
 267  *
 268  *      After stream initialization it is assigned a unique ID (within the front
 269  *      driver), so every stream of the frontend can be identified by the
 270  *      backend by this ID. This is not equal to stream-idx as the later is
 271  *      zero based within the device, but this index is contigous within the
 272  *      driver.
 273  *
 274  *-------------------- Stream Request Transport Parameters --------------------
 275  *
 276  * event-channel
 277  *      Values:         <uint32_t>
 278  *
 279  *      The identifier of the Xen event channel used to signal activity
 280  *      in the ring buffer.
 281  *
 282  * ring-ref
 283  *      Values:         <uint32_t>
 284  *
 285  *      The Xen grant reference granting permission for the backend to map
 286  *      a sole page in a single page sized ring buffer.
 287  *
 288  ******************************************************************************
 289  *                               STATE DIAGRAMS
 290  ******************************************************************************
 291  *
 292  * Tool stack creates front and back state nodes with initial state
 293  * XenbusStateInitialising.
 294  * Tool stack creates and sets up frontend sound configuration nodes per domain.
 295  *
 296  * Front                                Back
 297  * =================================    =====================================
 298  * XenbusStateInitialising              XenbusStateInitialising
 299  *                                       o Query backend device identification
 300  *                                         data.
 301  *                                       o Open and validate backend device.
 302  *                                                      |
 303  *                                                      |
 304  *                                                      V
 305  *                                      XenbusStateInitWait
 306  *
 307  * o Query frontend configuration
 308  * o Allocate and initialize
 309  *   event channels per configured
 310  *   playback/capture stream.
 311  * o Publish transport parameters
 312  *   that will be in effect during
 313  *   this connection.
 314  *              |
 315  *              |
 316  *              V
 317  * XenbusStateInitialised
 318  *
 319  *                                       o Query frontend transport parameters.
 320  *                                       o Connect to the event channels.
 321  *                                                      |
 322  *                                                      |
 323  *                                                      V
 324  *                                      XenbusStateConnected
 325  *
 326  *  o Create and initialize OS
 327  *    virtual sound device instances
 328  *    as per configuration.
 329  *              |
 330  *              |
 331  *              V
 332  * XenbusStateConnected
 333  *
 334  *                                      XenbusStateUnknown
 335  *                                      XenbusStateClosed
 336  *                                      XenbusStateClosing
 337  * o Remove virtual sound device
 338  * o Remove event channels
 339  *              |
 340  *              |
 341  *              V
 342  * XenbusStateClosed
 343  *
 344  *------------------------------- Recovery flow -------------------------------
 345  *
 346  * In case of frontend unrecoverable errors backend handles that as
 347  * if frontend goes into the XenbusStateClosed state.
 348  *
 349  * In case of backend unrecoverable errors frontend tries removing
 350  * the virtualized device. If this is possible at the moment of error,
 351  * then frontend goes into the XenbusStateInitialising state and is ready for
 352  * new connection with backend. If the virtualized device is still in use and
 353  * cannot be removed, then frontend goes into the XenbusStateReconfiguring state
 354  * until either the virtualized device removed or backend initiates a new
 355  * connection. On the virtualized device removal frontend goes into the
 356  * XenbusStateInitialising state.
 357  *
 358  * Note on XenbusStateReconfiguring state of the frontend: if backend has
 359  * unrecoverable errors then frontend cannot send requests to the backend
 360  * and thus cannot provide functionality of the virtualized device anymore.
 361  * After backend is back to normal the virtualized device may still hold some
 362  * state: configuration in use, allocated buffers, client application state etc.
 363  * So, in most cases, this will require frontend to implement complex recovery
 364  * reconnect logic. Instead, by going into XenbusStateReconfiguring state,
 365  * frontend will make sure no new clients of the virtualized device are
 366  * accepted, allow existing client(s) to exit gracefully by signaling error
 367  * state etc.
 368  * Once all the clients are gone frontend can reinitialize the virtualized
 369  * device and get into XenbusStateInitialising state again signaling the
 370  * backend that a new connection can be made.
 371  *
 372  * There are multiple conditions possible under which frontend will go from
 373  * XenbusStateReconfiguring into XenbusStateInitialising, some of them are OS
 374  * specific. For example:
 375  * 1. The underlying OS framework may provide callbacks to signal that the last
 376  *    client of the virtualized device has gone and the device can be removed
 377  * 2. Frontend can schedule a deferred work (timer/tasklet/workqueue)
 378  *    to periodically check if this is the right time to re-try removal of
 379  *    the virtualized device.
 380  * 3. By any other means.
 381  *
 382  ******************************************************************************
 383  *                             PCM FORMATS
 384  ******************************************************************************
 385  *
 386  * XENSND_PCM_FORMAT_<format>[_<endian>]
 387  *
 388  * format: <S/U/F><bits> or <name>
 389  *     S - signed, U - unsigned, F - float
 390  *     bits - 8, 16, 24, 32
 391  *     name - MU_LAW, GSM, etc.
 392  *
 393  * endian: <LE/BE>, may be absent
 394  *     LE - Little endian, BE - Big endian
 395  */
 396 #define XENSND_PCM_FORMAT_S8            0
 397 #define XENSND_PCM_FORMAT_U8            1
 398 #define XENSND_PCM_FORMAT_S16_LE        2
 399 #define XENSND_PCM_FORMAT_S16_BE        3
 400 #define XENSND_PCM_FORMAT_U16_LE        4
 401 #define XENSND_PCM_FORMAT_U16_BE        5
 402 #define XENSND_PCM_FORMAT_S24_LE        6
 403 #define XENSND_PCM_FORMAT_S24_BE        7
 404 #define XENSND_PCM_FORMAT_U24_LE        8
 405 #define XENSND_PCM_FORMAT_U24_BE        9
 406 #define XENSND_PCM_FORMAT_S32_LE        10
 407 #define XENSND_PCM_FORMAT_S32_BE        11
 408 #define XENSND_PCM_FORMAT_U32_LE        12
 409 #define XENSND_PCM_FORMAT_U32_BE        13
 410 #define XENSND_PCM_FORMAT_F32_LE        14 /* 4-byte float, IEEE-754 32-bit, */
 411 #define XENSND_PCM_FORMAT_F32_BE        15 /* range -1.0 to 1.0              */
 412 #define XENSND_PCM_FORMAT_F64_LE        16 /* 8-byte float, IEEE-754 64-bit, */
 413 #define XENSND_PCM_FORMAT_F64_BE        17 /* range -1.0 to 1.0              */
 414 #define XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE 18
 415 #define XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE 19
 416 #define XENSND_PCM_FORMAT_MU_LAW        20
 417 #define XENSND_PCM_FORMAT_A_LAW         21
 418 #define XENSND_PCM_FORMAT_IMA_ADPCM     22
 419 #define XENSND_PCM_FORMAT_MPEG          23
 420 #define XENSND_PCM_FORMAT_GSM           24
 421
 422 /*
 423  ******************************************************************************
 424  *                             REQUEST CODES
 425  ******************************************************************************
 426  */
 427 #define XENSND_OP_OPEN                  0
 428 #define XENSND_OP_CLOSE                 1
 429 #define XENSND_OP_READ                  2
 430 #define XENSND_OP_WRITE                 3
 431 #define XENSND_OP_SET_VOLUME            4
 432 #define XENSND_OP_GET_VOLUME            5
 433 #define XENSND_OP_MUTE                  6
 434 #define XENSND_OP_UNMUTE                7
 435
 436 /*
 437  ******************************************************************************
 438  *               XENSTORE FIELD AND PATH NAME STRINGS, HELPERS
 439  ******************************************************************************
 440  */
 441 #define XENSND_DRIVER_NAME              "vsnd"
 442
 443 #define XENSND_LIST_SEPARATOR           ","
 444 /* Field names */
 445 #define XENSND_FIELD_BE_VERSIONS        "versions"
 446 #define XENSND_FIELD_FE_VERSION         "version"
 447 #define XENSND_FIELD_VCARD_SHORT_NAME   "short-name"
 448 #define XENSND_FIELD_VCARD_LONG_NAME    "long-name"
 449 #define XENSND_FIELD_RING_REF           "ring-ref"
 450 #define XENSND_FIELD_EVT_CHNL           "event-channel"
 451 #define XENSND_FIELD_DEVICE_NAME        "name"
 452 #define XENSND_FIELD_TYPE               "type"
 453 #define XENSND_FIELD_STREAM_UNIQUE_ID   "unique-id"
 454 #define XENSND_FIELD_CHANNELS_MIN       "channels-min"
 455 #define XENSND_FIELD_CHANNELS_MAX       "channels-max"
 456 #define XENSND_FIELD_SAMPLE_RATES       "sample-rates"
 457 #define XENSND_FIELD_SAMPLE_FORMATS     "sample-formats"
 458 #define XENSND_FIELD_BUFFER_SIZE        "buffer-size"
 459
 460 /* Stream type field values. */
 461 #define XENSND_STREAM_TYPE_PLAYBACK     "p"
 462 #define XENSND_STREAM_TYPE_CAPTURE      "c"
 463 /* Sample rate max string length */
 464 #define XENSND_SAMPLE_RATE_MAX_LEN      11
 465 /* Sample format field values */
 466 #define XENSND_SAMPLE_FORMAT_MAX_LEN    24
 467
 468 #define XENSND_PCM_FORMAT_S8_STR        "s8"
 469 #define XENSND_PCM_FORMAT_U8_STR        "u8"
 470 #define XENSND_PCM_FORMAT_S16_LE_STR    "s16_le"
 471 #define XENSND_PCM_FORMAT_S16_BE_STR    "s16_be"
 472 #define XENSND_PCM_FORMAT_U16_LE_STR    "u16_le"
 473 #define XENSND_PCM_FORMAT_U16_BE_STR    "u16_be"
 474 #define XENSND_PCM_FORMAT_S24_LE_STR    "s24_le"
 475 #define XENSND_PCM_FORMAT_S24_BE_STR    "s24_be"
 476 #define XENSND_PCM_FORMAT_U24_LE_STR    "u24_le"
 477 #define XENSND_PCM_FORMAT_U24_BE_STR    "u24_be"
 478 #define XENSND_PCM_FORMAT_S32_LE_STR    "s32_le"
 479 #define XENSND_PCM_FORMAT_S32_BE_STR    "s32_be"
 480 #define XENSND_PCM_FORMAT_U32_LE_STR    "u32_le"
 481 #define XENSND_PCM_FORMAT_U32_BE_STR    "u32_be"
 482 #define XENSND_PCM_FORMAT_F32_LE_STR    "float_le"
 483 #define XENSND_PCM_FORMAT_F32_BE_STR    "float_be"
 484 #define XENSND_PCM_FORMAT_F64_LE_STR    "float64_le"
 485 #define XENSND_PCM_FORMAT_F64_BE_STR    "float64_be"
 486 #define XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE_STR "iec958_subframe_le"
 487 #define XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE_STR "iec958_subframe_be"
 488 #define XENSND_PCM_FORMAT_MU_LAW_STR    "mu_law"
 489 #define XENSND_PCM_FORMAT_A_LAW_STR     "a_law"
 490 #define XENSND_PCM_FORMAT_IMA_ADPCM_STR "ima_adpcm"
 491 #define XENSND_PCM_FORMAT_MPEG_STR      "mpeg"
 492 #define XENSND_PCM_FORMAT_GSM_STR       "gsm"
 493
 494
 495 /*
 496  ******************************************************************************
 497  *                          STATUS RETURN CODES
 498  ******************************************************************************
 499  *
 500  * Status return code is zero on success and -XEN_EXX on failure.
 501  *
 502  ******************************************************************************
 503  *                              Assumptions
 504  ******************************************************************************
 505  * o usage of grant reference 0 as invalid grant reference:
 506  *   grant reference 0 is valid, but never exposed to a PV driver,
 507  *   because of the fact it is already in use/reserved by the PV console.
 508  * o all references in this document to page sizes must be treated
 509  *   as pages of size XEN_PAGE_SIZE unless otherwise noted.
 510  *
 511  ******************************************************************************
 512  *       Description of the protocol between frontend and backend driver
 513  ******************************************************************************
 514  *
 515  * The two halves of a Para-virtual sound driver communicate with
 516  * each other using shared pages and event channels.
 517  * Shared page contains a ring with request/response packets.
 518  *
 519  * Packets, used for input/output operations, e.g. read/write, set/get volume,
 520  * etc., provide offset/length fields in order to allow asynchronous protocol
 521  * operation with buffer space sharing: part of the buffer allocated at
 522  * XENSND_OP_OPEN can be used for audio samples and part, for example,
 523  * for volume control.
 524  *
 525  * All reserved fields in the structures below must be 0.
 526  *
 527  *---------------------------------- Requests ---------------------------------
 528  *
 529  * All request packets have the same length (32 octets)
 530  * All request packets have common header:
 531  *         0                1                 2               3        octet
 532  * +----------------+----------------+----------------+----------------+
 533  * |               id                |    operation   |    reserved    | 4
 534  * +----------------+----------------+----------------+----------------+
 535  * |                             reserved                              | 8
 536  * +----------------+----------------+----------------+----------------+
 537  *   id - uint16_t, private guest value, echoed in response
 538  *   operation - uint8_t, operation code, XENSND_OP_???
 539  *
 540  * For all packets which use offset and length:
 541  *   offset - uint32_t, read or write data offset within the shared buffer,
 542  *     passed with XENSND_OP_OPEN request, octets,
 543  *     [0; XENSND_OP_OPEN.buffer_sz - 1].
 544  *   length - uint32_t, read or write data length, octets
 545  *
 546  * Request open - open a PCM stream for playback or capture:
 547  *
 548  *         0                1                 2               3        octet
 549  * +----------------+----------------+----------------+----------------+
 550  * |               id                | XENSND_OP_OPEN |    reserved    | 4
 551  * +----------------+----------------+----------------+----------------+
 552  * |                             reserved                              | 8
 553  * +----------------+----------------+----------------+----------------+
 554  * |                             pcm_rate                              | 12
 555  * +----------------+----------------+----------------+----------------+
 556  * |  pcm_format    |  pcm_channels  |             reserved            | 16
 557  * +----------------+----------------+----------------+----------------+
 558  * |                             buffer_sz                             | 20
 559  * +----------------+----------------+----------------+----------------+
 560  * |                           gref_directory                          | 24
 561  * +----------------+----------------+----------------+----------------+
 562  * |                             reserved                              | 28
 563  * +----------------+----------------+----------------+----------------+
 564  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 565  * +----------------+----------------+----------------+----------------+
 566  * |                             reserved                              | 32
 567  * +----------------+----------------+----------------+----------------+
 568  *
 569  * pcm_rate - uint32_t, stream data rate, Hz
 570  * pcm_format - uint8_t, XENSND_PCM_FORMAT_XXX value
 571  * pcm_channels - uint8_t, number of channels of this stream,
 572  *   [channels-min; channels-max]
 573  * buffer_sz - uint32_t, buffer size to be allocated, octets
 574  * gref_directory - grant_ref_t, a reference to the first shared page
 575  *   describing shared buffer references. At least one page exists. If shared
 576  *   buffer size  (buffer_sz) exceeds what can be addressed by this single page,
 577  *   then reference to the next page must be supplied (see gref_dir_next_page
 578  *   below)
 579  */
 580
 581 struct xensnd_open_req {
 582         uint32_t pcm_rate;
 583         uint8_t pcm_format;
 584         uint8_t pcm_channels;
 585         uint16_t reserved;
 586         uint32_t buffer_sz;
 587         grant_ref_t gref_directory;
 588 };
 589
 590 /*
 591  * Shared page for XENSND_OP_OPEN buffer descriptor (gref_directory in the
 592  *   request) employs a list of pages, describing all pages of the shared data
 593  *   buffer:
 594  *         0                1                 2               3        octet
 595  * +----------------+----------------+----------------+----------------+
 596  * |                        gref_dir_next_page                         | 4
 597  * +----------------+----------------+----------------+----------------+
 598  * |                              gref[0]                              | 8
 599  * +----------------+----------------+----------------+----------------+
 600  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 601  * +----------------+----------------+----------------+----------------+
 602  * |                              gref[i]                              | i*4+8
 603  * +----------------+----------------+----------------+----------------+
 604  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 605  * +----------------+----------------+----------------+----------------+
 606  * |                             gref[N - 1]                           | N*4+8
 607  * +----------------+----------------+----------------+----------------+
 608  *
 609  * gref_dir_next_page - grant_ref_t, reference to the next page describing
 610  *   page directory. Must be 0 if there are no more pages in the list.
 611  * gref[i] - grant_ref_t, reference to a shared page of the buffer
 612  *   allocated at XENSND_OP_OPEN
 613  *
 614  * Number of grant_ref_t entries in the whole page directory is not
 615  * passed, but instead can be calculated as:
 616  *   num_grefs_total = (XENSND_OP_OPEN.buffer_sz + XEN_PAGE_SIZE - 1) /
 617  *       XEN_PAGE_SIZE
 618  */
 619
 620 struct xensnd_page_directory {
 621         grant_ref_t gref_dir_next_page;
 622         grant_ref_t gref[1]; /* Variable length */
 623 };
 624
 625 /*
 626  *  Request close - close an opened pcm stream:
 627  *         0                1                 2               3        octet
 628  * +----------------+----------------+----------------+----------------+
 629  * |               id                | XENSND_OP_CLOSE|    reserved    | 4
 630  * +----------------+----------------+----------------+----------------+
 631  * |                             reserved                              | 8
 632  * +----------------+----------------+----------------+----------------+
 633  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 634  * +----------------+----------------+----------------+----------------+
 635  * |                             reserved                              | 32
 636  * +----------------+----------------+----------------+----------------+
 637  *
 638  * Request read/write - used for read (for capture) or write (for playback):
 639  *         0                1                 2               3        octet
 640  * +----------------+----------------+----------------+----------------+
 641  * |               id                |   operation    |    reserved    | 4
 642  * +----------------+----------------+----------------+----------------+
 643  * |                             reserved                              | 8
 644  * +----------------+----------------+----------------+----------------+
 645  * |                              offset                               | 12
 646  * +----------------+----------------+----------------+----------------+
 647  * |                              length                               | 16
 648  * +----------------+----------------+----------------+----------------+
 649  * |                             reserved                              | 20
 650  * +----------------+----------------+----------------+----------------+
 651  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 652  * +----------------+----------------+----------------+----------------+
 653  * |                             reserved                              | 32
 654  * +----------------+----------------+----------------+----------------+
 655  *
 656  * operation - XENSND_OP_READ for read or XENSND_OP_WRITE for write
 657  */
 658
 659 struct xensnd_rw_req {
 660         uint32_t offset;
 661         uint32_t length;
 662 };
 663
 664 /*
 665  * Request set/get volume - set/get channels' volume of the stream given:
 666  *         0                1                 2               3        octet
 667  * +----------------+----------------+----------------+----------------+
 668  * |               id                |   operation    |    reserved    | 4
 669  * +----------------+----------------+----------------+----------------+
 670  * |                             reserved                              | 8
 671  * +----------------+----------------+----------------+----------------+
 672  * |                              offset                               | 12
 673  * +----------------+----------------+----------------+----------------+
 674  * |                              length                               | 16
 675  * +----------------+----------------+----------------+----------------+
 676  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 677  * +----------------+----------------+----------------+----------------+
 678  * |                             reserved                              | 32
 679  * +----------------+----------------+----------------+----------------+
 680  *
 681  * operation - XENSND_OP_SET_VOLUME for volume set
 682  *   or XENSND_OP_GET_VOLUME for volume get
 683  * Buffer passed with XENSND_OP_OPEN is used to exchange volume
 684  * values:
 685  *
 686  *         0                1                 2               3        octet
 687  * +----------------+----------------+----------------+----------------+
 688  * |                             channel[0]                            | 4
 689  * +----------------+----------------+----------------+----------------+
 690  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 691  * +----------------+----------------+----------------+----------------+
 692  * |                             channel[i]                            | i*4
 693  * +----------------+----------------+----------------+----------------+
 694  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 695  * +----------------+----------------+----------------+----------------+
 696  * |                           channel[N - 1]                          | (N-1)*4
 697  * +----------------+----------------+----------------+----------------+
 698  *
 699  * N = XENSND_OP_OPEN.pcm_channels
 700  * i - uint8_t, index of a channel
 701  * channel[i] - sint32_t, volume of i-th channel
 702  * Volume is expressed as a signed value in steps of 0.001 dB,
 703  * while 0 being 0 dB.
 704  *
 705  * Request mute/unmute - mute/unmute stream:
 706  *         0                1                 2               3        octet
 707  * +----------------+----------------+----------------+----------------+
 708  * |               id                |   operation    |    reserved    | 4
 709  * +----------------+----------------+----------------+----------------+
 710  * |                             reserved                              | 8
 711  * +----------------+----------------+----------------+----------------+
 712  * |                              offset                               | 12
 713  * +----------------+----------------+----------------+----------------+
 714  * |                              length                               | 16
 715  * +----------------+----------------+----------------+----------------+
 716  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 717  * +----------------+----------------+----------------+----------------+
 718  * |                             reserved                              | 32
 719  * +----------------+----------------+----------------+----------------+
 720  *
 721  * operation - XENSND_OP_MUTE for mute or XENSND_OP_UNMUTE for unmute
 722  * Buffer passed with XENSND_OP_OPEN is used to exchange mute/unmute
 723  * values:
 724  *
 725  *                                   0                                 octet
 726  * +----------------+----------------+----------------+----------------+
 727  * |                             channel[0]                            | 4
 728  * +----------------+----------------+----------------+----------------+
 729  * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 730  * +----------------+----------------+----------------+----------------+
 731  * |                             channel[i]                            | i*4
 732  * +----------------+----------------+----------------+----------------+
 733  * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 734  * +----------------+----------------+----------------+----------------+
 735  * |                           channel[N - 1]                          | (N-1)*4
 736  * +----------------+----------------+----------------+----------------+
 737  *
 738  * N = XENSND_OP_OPEN.pcm_channels
 739  * i - uint8_t, index of a channel
 740  * channel[i] - uint8_t, non-zero if i-th channel needs to be muted/unmuted
 741  *
 742  *------------------------------------ N.B. -----------------------------------
 743  *
 744  * The 'struct xensnd_rw_req' is also used for XENSND_OP_SET_VOLUME,
 745  * XENSND_OP_GET_VOLUME, XENSND_OP_MUTE, XENSND_OP_UNMUTE.
 746  */
 747
 748 /*
 749  *---------------------------------- Responses --------------------------------
 750  *
 751  * All response packets have the same length (32 octets)
 752  *
 753  * Response for all requests:
 754  *         0                1                 2               3        octet
 755  * +----------------+----------------+----------------+----------------+
 756  * |               id                |    operation   |    reserved    | 4
 757  * +----------------+----------------+----------------+----------------+
 758  * |                              status                               | 8
 759  * +----------------+----------------+----------------+----------------+
 760  * |                             reserved                              | 12
 761  * +----------------+----------------+----------------+----------------+
 762  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 763  * +----------------+----------------+----------------+----------------+
 764  * |                             reserved                              | 32
 765  * +----------------+----------------+----------------+----------------+
 766  *
 767  * id - uint16_t, copied from the request
 768  * operation - uint8_t, XENSND_OP_* - copied from request
 769  * status - int32_t, response status, zero on success and -XEN_EXX on failure
 770  */
 771
 772 struct xensnd_req {
 773         uint16_t id;
 774         uint8_t operation;
 775         uint8_t reserved[5];
 776         union {
 777                 struct xensnd_open_req open;
 778                 struct xensnd_rw_req rw;
 779                 uint8_t reserved[24];
 780         } op;
 781 };
 782
 783 struct xensnd_resp {
 784         uint16_t id;
 785         uint8_t operation;
 786         uint8_t reserved;
 787         int32_t status;
 788         uint8_t reserved1[24];
 789 };
 790
 791 DEFINE_RING_TYPES(xen_sndif, struct xensnd_req, struct xensnd_resp);
 792
 793 #endif /* __XEN_PUBLIC_IO_SNDIF_H__ */