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  *                           Protocol version
  42  ******************************************************************************
  43  */
  44 #define XENSND_PROTOCOL_VERSION 2
  45
  46 /*
  47  ******************************************************************************
  48  *                  Feature and Parameter Negotiation
  49  ******************************************************************************
  50  *
  51  * Front->back notifications: when enqueuing a new request, sending a
  52  * notification can be made conditional on xensnd_req (i.e., the generic
  53  * hold-off mechanism provided by the ring macros). Backends must set
  54  * xensnd_req appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
  55  *
  56  * Back->front notifications: when enqueuing a new response, sending a
  57  * notification can be made conditional on xensnd_resp (i.e., the generic
  58  * hold-off mechanism provided by the ring macros). Frontends must set
  59  * xensnd_resp appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
  60  *
  61  * The two halves of a para-virtual sound card driver utilize nodes within
  62  * XenStore to communicate capabilities and to negotiate operating parameters.
  63  * This section enumerates these nodes which reside in the respective front and
  64  * backend portions of XenStore, following the XenBus convention.
  65  *
  66  * All data in XenStore is stored as strings. Nodes specifying numeric
  67  * values are encoded in decimal. Integer value ranges listed below are
  68  * expressed as fixed sized integer types capable of storing the conversion
  69  * of a properly formated node string, without loss of information.
  70  *
  71  ******************************************************************************
  72  *                        Example configuration
  73  ******************************************************************************
  74  *
  75  * Note: depending on the use-case backend can expose more sound cards and
  76  * PCM devices/streams than the underlying HW physically has by employing
  77  * SW mixers, configuring virtual sound streams, channels etc.
  78  *
  79  * This is an example of backend and frontend configuration:
  80  *
  81  *--------------------------------- Backend -----------------------------------
  82  *
  83  * /local/domain/0/backend/vsnd/1/0/frontend-id = "1"
  84  * /local/domain/0/backend/vsnd/1/0/frontend = "/local/domain/1/device/vsnd/0"
  85  * /local/domain/0/backend/vsnd/1/0/state = "4"
  86  * /local/domain/0/backend/vsnd/1/0/versions = "1,2"
  87  *
  88  *--------------------------------- Frontend ----------------------------------
  89  *
  90  * /local/domain/1/device/vsnd/0/backend-id = "0"
  91  * /local/domain/1/device/vsnd/0/backend = "/local/domain/0/backend/vsnd/1/0"
  92  * /local/domain/1/device/vsnd/0/state = "4"
  93  * /local/domain/1/device/vsnd/0/version = "1"
  94  *
  95  *----------------------------- Card configuration ----------------------------
  96  *
  97  * /local/domain/1/device/vsnd/0/short-name = "Card short name"
  98  * /local/domain/1/device/vsnd/0/long-name = "Card long name"
  99  * /local/domain/1/device/vsnd/0/sample-rates = "8000,32000,44100,48000,96000"
 100  * /local/domain/1/device/vsnd/0/sample-formats = "s8,u8,s16_le,s16_be"
 101  * /local/domain/1/device/vsnd/0/buffer-size = "262144"
 102  *
 103  *------------------------------- PCM device 0 --------------------------------
 104  *
 105  * /local/domain/1/device/vsnd/0/0/name = "General analog"
 106  * /local/domain/1/device/vsnd/0/0/channels-max = "5"
 107  *
 108  *----------------------------- Stream 0, playback ----------------------------
 109  *
 110  * /local/domain/1/device/vsnd/0/0/0/type = "p"
 111  * /local/domain/1/device/vsnd/0/0/0/sample-formats = "s8,u8"
 112  * /local/domain/1/device/vsnd/0/0/0/unique-id = "0"
 113  *
 114  * /local/domain/1/device/vsnd/0/0/0/ring-ref = "386"
 115  * /local/domain/1/device/vsnd/0/0/0/event-channel = "15"
 116  * /local/domain/1/device/vsnd/0/0/0/evt-ring-ref = "1386"
 117  * /local/domain/1/device/vsnd/0/0/0/evt-event-channel = "215"
 118  *
 119  *------------------------------ Stream 1, capture ----------------------------
 120  *
 121  * /local/domain/1/device/vsnd/0/0/1/type = "c"
 122  * /local/domain/1/device/vsnd/0/0/1/channels-max = "2"
 123  * /local/domain/1/device/vsnd/0/0/1/unique-id = "1"
 124  *
 125  * /local/domain/1/device/vsnd/0/0/1/ring-ref = "384"
 126  * /local/domain/1/device/vsnd/0/0/1/event-channel = "13"
 127  * /local/domain/1/device/vsnd/0/0/1/evt-ring-ref = "1384"
 128  * /local/domain/1/device/vsnd/0/0/1/evt-event-channel = "213"
 129  *
 130  *------------------------------- PCM device 1 --------------------------------
 131  *
 132  * /local/domain/1/device/vsnd/0/1/name = "HDMI-0"
 133  * /local/domain/1/device/vsnd/0/1/sample-rates = "8000,32000,44100"
 134  *
 135  *------------------------------ Stream 0, capture ----------------------------
 136  *
 137  * /local/domain/1/device/vsnd/0/1/0/type = "c"
 138  * /local/domain/1/device/vsnd/0/1/0/unique-id = "2"
 139  *
 140  * /local/domain/1/device/vsnd/0/1/0/ring-ref = "387"
 141  * /local/domain/1/device/vsnd/0/1/0/event-channel = "151"
 142  * /local/domain/1/device/vsnd/0/1/0/evt-ring-ref = "1387"
 143  * /local/domain/1/device/vsnd/0/1/0/evt-event-channel = "351"
 144  *
 145  *------------------------------- PCM device 2 --------------------------------
 146  *
 147  * /local/domain/1/device/vsnd/0/2/name = "SPDIF"
 148  *
 149  *----------------------------- Stream 0, playback ----------------------------
 150  *
 151  * /local/domain/1/device/vsnd/0/2/0/type = "p"
 152  * /local/domain/1/device/vsnd/0/2/0/unique-id = "3"
 153  *
 154  * /local/domain/1/device/vsnd/0/2/0/ring-ref = "389"
 155  * /local/domain/1/device/vsnd/0/2/0/event-channel = "152"
 156  * /local/domain/1/device/vsnd/0/2/0/evt-ring-ref = "1389"
 157  * /local/domain/1/device/vsnd/0/2/0/evt-event-channel = "452"
 158  *
 159  ******************************************************************************
 160  *                            Backend XenBus Nodes
 161  ******************************************************************************
 162  *
 163  *----------------------------- Protocol version ------------------------------
 164  *
 165  * versions
 166  *      Values:         <string>
 167  *
 168  *      List of XENSND_LIST_SEPARATOR separated protocol versions supported
 169  *      by the backend. For example "1,2,3".
 170  *
 171  ******************************************************************************
 172  *                            Frontend XenBus Nodes
 173  ******************************************************************************
 174  *
 175  *-------------------------------- Addressing ---------------------------------
 176  *
 177  * dom-id
 178  *      Values:         <uint16_t>
 179  *
 180  *      Domain identifier.
 181  *
 182  * dev-id
 183  *      Values:         <uint16_t>
 184  *
 185  *      Device identifier.
 186  *
 187  * pcm-dev-idx
 188  *      Values:         <uint8_t>
 189  *
 190  *      Zero based contigous index of the PCM device.
 191  *
 192  * stream-idx
 193  *      Values:         <uint8_t>
 194  *
 195  *      Zero based contigous index of the stream of the PCM device.
 196  *
 197  * The following pattern is used for addressing:
 198  *   /local/domain/<dom-id>/device/vsnd/<dev-id>/<pcm-dev-idx>/<stream-idx>/...
 199  *
 200  *----------------------------- Protocol version ------------------------------
 201  *
 202  * version
 203  *      Values:         <string>
 204  *
 205  *      Protocol version, chosen among the ones supported by the backend.
 206  *
 207  *------------------------------- PCM settings --------------------------------
 208  *
 209  * Every virtualized sound frontend has a set of PCM devices and streams, each
 210  * could be individually configured. Part of the PCM configuration can be
 211  * defined at higher level of the hierarchy and be fully or partially re-used
 212  * by the underlying layers. These configuration values are:
 213  *  o number of channels (min/max)
 214  *  o supported sample rates
 215  *  o supported sample formats.
 216  * E.g. one can define these values for the whole card, device or stream.
 217  * Every underlying layer in turn can re-define some or all of them to better
 218  * fit its needs. For example, card may define number of channels to be
 219  * in [1; 8] range, and some particular stream may be limited to [1; 2] only.
 220  * The rule is that the underlying layer must be a subset of the upper layer
 221  * range.
 222  *
 223  * channels-min
 224  *      Values:         <uint8_t>
 225  *
 226  *      The minimum amount of channels that is supported, [1; channels-max].
 227  *      Optional, if not set or omitted a value of 1 is used.
 228  *
 229  * channels-max
 230  *      Values:         <uint8_t>
 231  *
 232  *      The maximum amount of channels that is supported.
 233  *      Must be at least <channels-min>.
 234  *
 235  * sample-rates
 236  *      Values:         <list of uint32_t>
 237  *
 238  *      List of supported sample rates separated by XENSND_LIST_SEPARATOR.
 239  *      Sample rates are expressed as a list of decimal values w/o any
 240  *      ordering requirement.
 241  *
 242  * sample-formats
 243  *      Values:         <list of XENSND_PCM_FORMAT_XXX_STR>
 244  *
 245  *      List of supported sample formats separated by XENSND_LIST_SEPARATOR.
 246  *      Items must not exceed XENSND_SAMPLE_FORMAT_MAX_LEN length.
 247  *
 248  * buffer-size
 249  *      Values:         <uint32_t>
 250  *
 251  *      The maximum size in octets of the buffer to allocate per stream.
 252  *
 253  *----------------------- Virtual sound card settings -------------------------
 254  * short-name
 255  *      Values:         <char[32]>
 256  *
 257  *      Short name of the virtual sound card. Optional.
 258  *
 259  * long-name
 260  *      Values:         <char[80]>
 261  *
 262  *      Long name of the virtual sound card. Optional.
 263  *
 264  *----------------------------- Device settings -------------------------------
 265  * name
 266  *      Values:         <char[80]>
 267  *
 268  *      Name of the sound device within the virtual sound card. Optional.
 269  *
 270  *----------------------------- Stream settings -------------------------------
 271  *
 272  * type
 273  *      Values:         "p", "c"
 274  *
 275  *      Stream type: "p" - playback stream, "c" - capture stream
 276  *
 277  *      If both capture and playback are needed then two streams need to be
 278  *      defined under the same device.
 279  *
 280  * unique-id
 281  *      Values:         <string>
 282  *
 283  *      After stream initialization it is assigned a unique ID, so every
 284  *      stream of the frontend can be identified by the backend by this ID.
 285  *      This can be UUID or such.
 286  *
 287  *-------------------- Stream Request Transport Parameters --------------------
 288  *
 289  * event-channel
 290  *      Values:         <uint32_t>
 291  *
 292  *      The identifier of the Xen event channel used to signal activity
 293  *      in the ring buffer.
 294  *
 295  * ring-ref
 296  *      Values:         <uint32_t>
 297  *
 298  *      The Xen grant reference granting permission for the backend to map
 299  *      a sole page in a single page sized ring buffer.
 300  *
 301  *--------------------- Stream Event Transport Parameters ---------------------
 302  *
 303  * This communication path is used to deliver asynchronous events from backend
 304  * to frontend, set up per stream.
 305  *
 306  * evt-event-channel
 307  *      Values:         <uint32_t>
 308  *
 309  *      The identifier of the Xen event channel used to signal activity
 310  *      in the ring buffer.
 311  *
 312  * evt-ring-ref
 313  *      Values:         <uint32_t>
 314  *
 315  *      The Xen grant reference granting permission for the backend to map
 316  *      a sole page in a single page sized ring buffer.
 317  *
 318  ******************************************************************************
 319  *                               STATE DIAGRAMS
 320  ******************************************************************************
 321  *
 322  * Tool stack creates front and back state nodes with initial state
 323  * XenbusStateInitialising.
 324  * Tool stack creates and sets up frontend sound configuration nodes per domain.
 325  *
 326  * Front                                Back
 327  * =================================    =====================================
 328  * XenbusStateInitialising              XenbusStateInitialising
 329  *                                       o Query backend device identification
 330  *                                         data.
 331  *                                       o Open and validate backend device.
 332  *                                                      |
 333  *                                                      |
 334  *                                                      V
 335  *                                      XenbusStateInitWait
 336  *
 337  * o Query frontend configuration
 338  * o Allocate and initialize
 339  *   event channels per configured
 340  *   playback/capture stream.
 341  * o Publish transport parameters
 342  *   that will be in effect during
 343  *   this connection.
 344  *              |
 345  *              |
 346  *              V
 347  * XenbusStateInitialised
 348  *
 349  *                                       o Query frontend transport parameters.
 350  *                                       o Connect to the event channels.
 351  *                                                      |
 352  *                                                      |
 353  *                                                      V
 354  *                                      XenbusStateConnected
 355  *
 356  *  o Create and initialize OS
 357  *    virtual sound device instances
 358  *    as per configuration.
 359  *              |
 360  *              |
 361  *              V
 362  * XenbusStateConnected
 363  *
 364  *                                      XenbusStateUnknown
 365  *                                      XenbusStateClosed
 366  *                                      XenbusStateClosing
 367  * o Remove virtual sound device
 368  * o Remove event channels
 369  *              |
 370  *              |
 371  *              V
 372  * XenbusStateClosed
 373  *
 374  *------------------------------- Recovery flow -------------------------------
 375  *
 376  * In case of frontend unrecoverable errors backend handles that as
 377  * if frontend goes into the XenbusStateClosed state.
 378  *
 379  * In case of backend unrecoverable errors frontend tries removing
 380  * the virtualized device. If this is possible at the moment of error,
 381  * then frontend goes into the XenbusStateInitialising state and is ready for
 382  * new connection with backend. If the virtualized device is still in use and
 383  * cannot be removed, then frontend goes into the XenbusStateReconfiguring state
 384  * until either the virtualized device removed or backend initiates a new
 385  * connection. On the virtualized device removal frontend goes into the
 386  * XenbusStateInitialising state.
 387  *
 388  * Note on XenbusStateReconfiguring state of the frontend: if backend has
 389  * unrecoverable errors then frontend cannot send requests to the backend
 390  * and thus cannot provide functionality of the virtualized device anymore.
 391  * After backend is back to normal the virtualized device may still hold some
 392  * state: configuration in use, allocated buffers, client application state etc.
 393  * So, in most cases, this will require frontend to implement complex recovery
 394  * reconnect logic. Instead, by going into XenbusStateReconfiguring state,
 395  * frontend will make sure no new clients of the virtualized device are
 396  * accepted, allow existing client(s) to exit gracefully by signaling error
 397  * state etc.
 398  * Once all the clients are gone frontend can reinitialize the virtualized
 399  * device and get into XenbusStateInitialising state again signaling the
 400  * backend that a new connection can be made.
 401  *
 402  * There are multiple conditions possible under which frontend will go from
 403  * XenbusStateReconfiguring into XenbusStateInitialising, some of them are OS
 404  * specific. For example:
 405  * 1. The underlying OS framework may provide callbacks to signal that the last
 406  *    client of the virtualized device has gone and the device can be removed
 407  * 2. Frontend can schedule a deferred work (timer/tasklet/workqueue)
 408  *    to periodically check if this is the right time to re-try removal of
 409  *    the virtualized device.
 410  * 3. By any other means.
 411  *
 412  ******************************************************************************
 413  *                             PCM FORMATS
 414  ******************************************************************************
 415  *
 416  * XENSND_PCM_FORMAT_<format>[_<endian>]
 417  *
 418  * format: <S/U/F><bits> or <name>
 419  *     S - signed, U - unsigned, F - float
 420  *     bits - 8, 16, 24, 32
 421  *     name - MU_LAW, GSM, etc.
 422  *
 423  * endian: <LE/BE>, may be absent
 424  *     LE - Little endian, BE - Big endian
 425  */
 426 #define XENSND_PCM_FORMAT_S8            0
 427 #define XENSND_PCM_FORMAT_U8            1
 428 #define XENSND_PCM_FORMAT_S16_LE        2
 429 #define XENSND_PCM_FORMAT_S16_BE        3
 430 #define XENSND_PCM_FORMAT_U16_LE        4
 431 #define XENSND_PCM_FORMAT_U16_BE        5
 432 #define XENSND_PCM_FORMAT_S24_LE        6
 433 #define XENSND_PCM_FORMAT_S24_BE        7
 434 #define XENSND_PCM_FORMAT_U24_LE        8
 435 #define XENSND_PCM_FORMAT_U24_BE        9
 436 #define XENSND_PCM_FORMAT_S32_LE        10
 437 #define XENSND_PCM_FORMAT_S32_BE        11
 438 #define XENSND_PCM_FORMAT_U32_LE        12
 439 #define XENSND_PCM_FORMAT_U32_BE        13
 440 #define XENSND_PCM_FORMAT_F32_LE        14 /* 4-byte float, IEEE-754 32-bit, */
 441 #define XENSND_PCM_FORMAT_F32_BE        15 /* range -1.0 to 1.0              */
 442 #define XENSND_PCM_FORMAT_F64_LE        16 /* 8-byte float, IEEE-754 64-bit, */
 443 #define XENSND_PCM_FORMAT_F64_BE        17 /* range -1.0 to 1.0              */
 444 #define XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE 18
 445 #define XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE 19
 446 #define XENSND_PCM_FORMAT_MU_LAW        20
 447 #define XENSND_PCM_FORMAT_A_LAW         21
 448 #define XENSND_PCM_FORMAT_IMA_ADPCM     22
 449 #define XENSND_PCM_FORMAT_MPEG          23
 450 #define XENSND_PCM_FORMAT_GSM           24
 451
 452 /*
 453  ******************************************************************************
 454  *                             REQUEST CODES
 455  ******************************************************************************
 456  */
 457 #define XENSND_OP_OPEN                  0
 458 #define XENSND_OP_CLOSE                 1
 459 #define XENSND_OP_READ                  2
 460 #define XENSND_OP_WRITE                 3
 461 #define XENSND_OP_SET_VOLUME            4
 462 #define XENSND_OP_GET_VOLUME            5
 463 #define XENSND_OP_MUTE                  6
 464 #define XENSND_OP_UNMUTE                7
 465 #define XENSND_OP_TRIGGER               8
 466 #define XENSND_OP_HW_PARAM_QUERY        9
 467
 468 #define XENSND_OP_TRIGGER_START         0
 469 #define XENSND_OP_TRIGGER_PAUSE         1
 470 #define XENSND_OP_TRIGGER_STOP          2
 471 #define XENSND_OP_TRIGGER_RESUME        3
 472
 473 /*
 474  ******************************************************************************
 475  *                                 EVENT CODES
 476  ******************************************************************************
 477  */
 478 #define XENSND_EVT_CUR_POS              0
 479
 480 /*
 481  ******************************************************************************
 482  *               XENSTORE FIELD AND PATH NAME STRINGS, HELPERS
 483  ******************************************************************************
 484  */
 485 #define XENSND_DRIVER_NAME              "vsnd"
 486
 487 #define XENSND_LIST_SEPARATOR           ","
 488 /* Field names */
 489 #define XENSND_FIELD_BE_VERSIONS        "versions"
 490 #define XENSND_FIELD_FE_VERSION         "version"
 491 #define XENSND_FIELD_VCARD_SHORT_NAME   "short-name"
 492 #define XENSND_FIELD_VCARD_LONG_NAME    "long-name"
 493 #define XENSND_FIELD_RING_REF           "ring-ref"
 494 #define XENSND_FIELD_EVT_CHNL           "event-channel"
 495 #define XENSND_FIELD_EVT_RING_REF       "evt-ring-ref"
 496 #define XENSND_FIELD_EVT_EVT_CHNL       "evt-event-channel"
 497 #define XENSND_FIELD_DEVICE_NAME        "name"
 498 #define XENSND_FIELD_TYPE               "type"
 499 #define XENSND_FIELD_STREAM_UNIQUE_ID   "unique-id"
 500 #define XENSND_FIELD_CHANNELS_MIN       "channels-min"
 501 #define XENSND_FIELD_CHANNELS_MAX       "channels-max"
 502 #define XENSND_FIELD_SAMPLE_RATES       "sample-rates"
 503 #define XENSND_FIELD_SAMPLE_FORMATS     "sample-formats"
 504 #define XENSND_FIELD_BUFFER_SIZE        "buffer-size"
 505
 506 /* Stream type field values. */
 507 #define XENSND_STREAM_TYPE_PLAYBACK     "p"
 508 #define XENSND_STREAM_TYPE_CAPTURE      "c"
 509 /* Sample rate max string length */
 510 #define XENSND_SAMPLE_RATE_MAX_LEN      11
 511 /* Sample format field values */
 512 #define XENSND_SAMPLE_FORMAT_MAX_LEN    24
 513
 514 #define XENSND_PCM_FORMAT_S8_STR        "s8"
 515 #define XENSND_PCM_FORMAT_U8_STR        "u8"
 516 #define XENSND_PCM_FORMAT_S16_LE_STR    "s16_le"
 517 #define XENSND_PCM_FORMAT_S16_BE_STR    "s16_be"
 518 #define XENSND_PCM_FORMAT_U16_LE_STR    "u16_le"
 519 #define XENSND_PCM_FORMAT_U16_BE_STR    "u16_be"
 520 #define XENSND_PCM_FORMAT_S24_LE_STR    "s24_le"
 521 #define XENSND_PCM_FORMAT_S24_BE_STR    "s24_be"
 522 #define XENSND_PCM_FORMAT_U24_LE_STR    "u24_le"
 523 #define XENSND_PCM_FORMAT_U24_BE_STR    "u24_be"
 524 #define XENSND_PCM_FORMAT_S32_LE_STR    "s32_le"
 525 #define XENSND_PCM_FORMAT_S32_BE_STR    "s32_be"
 526 #define XENSND_PCM_FORMAT_U32_LE_STR    "u32_le"
 527 #define XENSND_PCM_FORMAT_U32_BE_STR    "u32_be"
 528 #define XENSND_PCM_FORMAT_F32_LE_STR    "float_le"
 529 #define XENSND_PCM_FORMAT_F32_BE_STR    "float_be"
 530 #define XENSND_PCM_FORMAT_F64_LE_STR    "float64_le"
 531 #define XENSND_PCM_FORMAT_F64_BE_STR    "float64_be"
 532 #define XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE_STR "iec958_subframe_le"
 533 #define XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE_STR "iec958_subframe_be"
 534 #define XENSND_PCM_FORMAT_MU_LAW_STR    "mu_law"
 535 #define XENSND_PCM_FORMAT_A_LAW_STR     "a_law"
 536 #define XENSND_PCM_FORMAT_IMA_ADPCM_STR "ima_adpcm"
 537 #define XENSND_PCM_FORMAT_MPEG_STR      "mpeg"
 538 #define XENSND_PCM_FORMAT_GSM_STR       "gsm"
 539
 540
 541 /*
 542  ******************************************************************************
 543  *                          STATUS RETURN CODES
 544  ******************************************************************************
 545  *
 546  * Status return code is zero on success and -XEN_EXX on failure.
 547  *
 548  ******************************************************************************
 549  *                              Assumptions
 550  ******************************************************************************
 551  * o usage of grant reference 0 as invalid grant reference:
 552  *   grant reference 0 is valid, but never exposed to a PV driver,
 553  *   because of the fact it is already in use/reserved by the PV console.
 554  * o all references in this document to page sizes must be treated
 555  *   as pages of size XEN_PAGE_SIZE unless otherwise noted.
 556  *
 557  ******************************************************************************
 558  *       Description of the protocol between frontend and backend driver
 559  ******************************************************************************
 560  *
 561  * The two halves of a Para-virtual sound driver communicate with
 562  * each other using shared pages and event channels.
 563  * Shared page contains a ring with request/response packets.
 564  *
 565  * Packets, used for input/output operations, e.g. read/write, set/get volume,
 566  * etc., provide offset/length fields in order to allow asynchronous protocol
 567  * operation with buffer space sharing: part of the buffer allocated at
 568  * XENSND_OP_OPEN can be used for audio samples and part, for example,
 569  * for volume control.
 570  *
 571  * All reserved fields in the structures below must be 0.
 572  *
 573  *---------------------------------- Requests ---------------------------------
 574  *
 575  * All request packets have the same length (64 octets)
 576  * All request packets have common header:
 577  *         0                1                 2               3        octet
 578  * +----------------+----------------+----------------+----------------+
 579  * |               id                |    operation   |    reserved    | 4
 580  * +----------------+----------------+----------------+----------------+
 581  * |                             reserved                              | 8
 582  * +----------------+----------------+----------------+----------------+
 583  *   id - uint16_t, private guest value, echoed in response
 584  *   operation - uint8_t, operation code, XENSND_OP_???
 585  *
 586  * For all packets which use offset and length:
 587  *   offset - uint32_t, read or write data offset within the shared buffer,
 588  *     passed with XENSND_OP_OPEN request, octets,
 589  *     [0; XENSND_OP_OPEN.buffer_sz - 1].
 590  *   length - uint32_t, read or write data length, octets
 591  *
 592  * Request open - open a PCM stream for playback or capture:
 593  *
 594  *         0                1                 2               3        octet
 595  * +----------------+----------------+----------------+----------------+
 596  * |               id                | XENSND_OP_OPEN |    reserved    | 4
 597  * +----------------+----------------+----------------+----------------+
 598  * |                             reserved                              | 8
 599  * +----------------+----------------+----------------+----------------+
 600  * |                             pcm_rate                              | 12
 601  * +----------------+----------------+----------------+----------------+
 602  * |  pcm_format    |  pcm_channels  |             reserved            | 16
 603  * +----------------+----------------+----------------+----------------+
 604  * |                             buffer_sz                             | 20
 605  * +----------------+----------------+----------------+----------------+
 606  * |                           gref_directory                          | 24
 607  * +----------------+----------------+----------------+----------------+
 608  * |                             period_sz                             | 28
 609  * +----------------+----------------+----------------+----------------+
 610  * |                             reserved                              | 32
 611  * +----------------+----------------+----------------+----------------+
 612  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 613  * +----------------+----------------+----------------+----------------+
 614  * |                             reserved                              | 64
 615  * +----------------+----------------+----------------+----------------+
 616  *
 617  * pcm_rate - uint32_t, stream data rate, Hz
 618  * pcm_format - uint8_t, XENSND_PCM_FORMAT_XXX value
 619  * pcm_channels - uint8_t, number of channels of this stream,
 620  *   [channels-min; channels-max]
 621  * buffer_sz - uint32_t, buffer size to be allocated, octets
 622  * period_sz - uint32_t, event period size, octets
 623  *   This is the requested value of the period at which frontend would
 624  *   like to receive XENSND_EVT_CUR_POS notifications from the backend when
 625  *   stream position advances during playback/capture.
 626  *   It shows how many octets are expected to be played/captured before
 627  *   sending such an event.
 628  *   If set to 0 no XENSND_EVT_CUR_POS events are sent by the backend.
 629  *
 630  * gref_directory - grant_ref_t, a reference to the first shared page
 631  *   describing shared buffer references. At least one page exists. If shared
 632  *   buffer size  (buffer_sz) exceeds what can be addressed by this single page,
 633  *   then reference to the next page must be supplied (see gref_dir_next_page
 634  *   below)
 635  */
 636
 637 struct xensnd_open_req {
 638         uint32_t pcm_rate;
 639         uint8_t pcm_format;
 640         uint8_t pcm_channels;
 641         uint16_t reserved;
 642         uint32_t buffer_sz;
 643         grant_ref_t gref_directory;
 644         uint32_t period_sz;
 645 };
 646
 647 /*
 648  * Shared page for XENSND_OP_OPEN buffer descriptor (gref_directory in the
 649  *   request) employs a list of pages, describing all pages of the shared data
 650  *   buffer:
 651  *         0                1                 2               3        octet
 652  * +----------------+----------------+----------------+----------------+
 653  * |                        gref_dir_next_page                         | 4
 654  * +----------------+----------------+----------------+----------------+
 655  * |                              gref[0]                              | 8
 656  * +----------------+----------------+----------------+----------------+
 657  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 658  * +----------------+----------------+----------------+----------------+
 659  * |                              gref[i]                              | i*4+8
 660  * +----------------+----------------+----------------+----------------+
 661  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 662  * +----------------+----------------+----------------+----------------+
 663  * |                             gref[N - 1]                           | N*4+8
 664  * +----------------+----------------+----------------+----------------+
 665  *
 666  * gref_dir_next_page - grant_ref_t, reference to the next page describing
 667  *   page directory. Must be 0 if there are no more pages in the list.
 668  * gref[i] - grant_ref_t, reference to a shared page of the buffer
 669  *   allocated at XENSND_OP_OPEN
 670  *
 671  * Number of grant_ref_t entries in the whole page directory is not
 672  * passed, but instead can be calculated as:
 673  *   num_grefs_total = (XENSND_OP_OPEN.buffer_sz + XEN_PAGE_SIZE - 1) /
 674  *       XEN_PAGE_SIZE
 675  */
 676
 677 struct xensnd_page_directory {
 678         grant_ref_t gref_dir_next_page;
 679         grant_ref_t gref[1]; /* Variable length */
 680 };
 681
 682 /*
 683  *  Request close - close an opened pcm stream:
 684  *         0                1                 2               3        octet
 685  * +----------------+----------------+----------------+----------------+
 686  * |               id                | XENSND_OP_CLOSE|    reserved    | 4
 687  * +----------------+----------------+----------------+----------------+
 688  * |                             reserved                              | 8
 689  * +----------------+----------------+----------------+----------------+
 690  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 691  * +----------------+----------------+----------------+----------------+
 692  * |                             reserved                              | 64
 693  * +----------------+----------------+----------------+----------------+
 694  *
 695  * Request read/write - used for read (for capture) or write (for playback):
 696  *         0                1                 2               3        octet
 697  * +----------------+----------------+----------------+----------------+
 698  * |               id                |   operation    |    reserved    | 4
 699  * +----------------+----------------+----------------+----------------+
 700  * |                             reserved                              | 8
 701  * +----------------+----------------+----------------+----------------+
 702  * |                              offset                               | 12
 703  * +----------------+----------------+----------------+----------------+
 704  * |                              length                               | 16
 705  * +----------------+----------------+----------------+----------------+
 706  * |                             reserved                              | 20
 707  * +----------------+----------------+----------------+----------------+
 708  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 709  * +----------------+----------------+----------------+----------------+
 710  * |                             reserved                              | 64
 711  * +----------------+----------------+----------------+----------------+
 712  *
 713  * operation - XENSND_OP_READ for read or XENSND_OP_WRITE for write
 714  */
 715
 716 struct xensnd_rw_req {
 717         uint32_t offset;
 718         uint32_t length;
 719 };
 720
 721 /*
 722  * Request set/get volume - set/get channels' volume of the stream given:
 723  *         0                1                 2               3        octet
 724  * +----------------+----------------+----------------+----------------+
 725  * |               id                |   operation    |    reserved    | 4
 726  * +----------------+----------------+----------------+----------------+
 727  * |                             reserved                              | 8
 728  * +----------------+----------------+----------------+----------------+
 729  * |                              offset                               | 12
 730  * +----------------+----------------+----------------+----------------+
 731  * |                              length                               | 16
 732  * +----------------+----------------+----------------+----------------+
 733  * |                             reserved                              | 20
 734  * +----------------+----------------+----------------+----------------+
 735  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 736  * +----------------+----------------+----------------+----------------+
 737  * |                             reserved                              | 64
 738  * +----------------+----------------+----------------+----------------+
 739  *
 740  * operation - XENSND_OP_SET_VOLUME for volume set
 741  *   or XENSND_OP_GET_VOLUME for volume get
 742  * Buffer passed with XENSND_OP_OPEN is used to exchange volume
 743  * values:
 744  *
 745  *         0                1                 2               3        octet
 746  * +----------------+----------------+----------------+----------------+
 747  * |                             channel[0]                            | 4
 748  * +----------------+----------------+----------------+----------------+
 749  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 750  * +----------------+----------------+----------------+----------------+
 751  * |                             channel[i]                            | i*4
 752  * +----------------+----------------+----------------+----------------+
 753  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 754  * +----------------+----------------+----------------+----------------+
 755  * |                           channel[N - 1]                          | (N-1)*4
 756  * +----------------+----------------+----------------+----------------+
 757  *
 758  * N = XENSND_OP_OPEN.pcm_channels
 759  * i - uint8_t, index of a channel
 760  * channel[i] - sint32_t, volume of i-th channel
 761  * Volume is expressed as a signed value in steps of 0.001 dB,
 762  * while 0 being 0 dB.
 763  *
 764  * Request mute/unmute - mute/unmute stream:
 765  *         0                1                 2               3        octet
 766  * +----------------+----------------+----------------+----------------+
 767  * |               id                |   operation    |    reserved    | 4
 768  * +----------------+----------------+----------------+----------------+
 769  * |                             reserved                              | 8
 770  * +----------------+----------------+----------------+----------------+
 771  * |                              offset                               | 12
 772  * +----------------+----------------+----------------+----------------+
 773  * |                              length                               | 16
 774  * +----------------+----------------+----------------+----------------+
 775  * |                             reserved                              | 20
 776  * +----------------+----------------+----------------+----------------+
 777  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 778  * +----------------+----------------+----------------+----------------+
 779  * |                             reserved                              | 64
 780  * +----------------+----------------+----------------+----------------+
 781  *
 782  * operation - XENSND_OP_MUTE for mute or XENSND_OP_UNMUTE for unmute
 783  * Buffer passed with XENSND_OP_OPEN is used to exchange mute/unmute
 784  * values:
 785  *
 786  *                                   0                                 octet
 787  * +----------------+----------------+----------------+----------------+
 788  * |                             channel[0]                            | 4
 789  * +----------------+----------------+----------------+----------------+
 790  * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 791  * +----------------+----------------+----------------+----------------+
 792  * |                             channel[i]                            | i*4
 793  * +----------------+----------------+----------------+----------------+
 794  * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 795  * +----------------+----------------+----------------+----------------+
 796  * |                           channel[N - 1]                          | (N-1)*4
 797  * +----------------+----------------+----------------+----------------+
 798  *
 799  * N = XENSND_OP_OPEN.pcm_channels
 800  * i - uint8_t, index of a channel
 801  * channel[i] - uint8_t, non-zero if i-th channel needs to be muted/unmuted
 802  *
 803  *------------------------------------ N.B. -----------------------------------
 804  *
 805  * The 'struct xensnd_rw_req' is also used for XENSND_OP_SET_VOLUME,
 806  * XENSND_OP_GET_VOLUME, XENSND_OP_MUTE, XENSND_OP_UNMUTE.
 807  *
 808  * Request stream running state change - trigger PCM stream running state
 809  * to start, stop, pause or resume:
 810  *
 811  *         0                1                 2               3        octet
 812  * +----------------+----------------+----------------+----------------+
 813  * |               id                |   _OP_TRIGGER  |    reserved    | 4
 814  * +----------------+----------------+----------------+----------------+
 815  * |                             reserved                              | 8
 816  * +----------------+----------------+----------------+----------------+
 817  * |      type      |                     reserved                     | 12
 818  * +----------------+----------------+----------------+----------------+
 819  * |                             reserved                              | 16
 820  * +----------------+----------------+----------------+----------------+
 821  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 822  * +----------------+----------------+----------------+----------------+
 823  * |                             reserved                              | 64
 824  * +----------------+----------------+----------------+----------------+
 825  *
 826  * type - uint8_t, XENSND_OP_TRIGGER_XXX value
 827  */
 828
 829 struct xensnd_trigger_req {
 830         uint8_t type;
 831 };
 832
 833 /*
 834  * Request stream parameter ranges: request intervals and
 835  *   masks of supported ranges for stream configuration values.
 836  *
 837  *   Sound device configuration for a particular stream is a limited subset
 838  *   of the multidimensional configuration available on XenStore, e.g.
 839  *   once the frame rate has been selected there is a limited supported range
 840  *   for sample rates becomes available (which might be the same set configured
 841  *   on XenStore or less). For example, selecting 96kHz sample rate may limit
 842  *   number of channels available for such configuration from 4 to 2, etc.
 843  *   Thus, each call to XENSND_OP_HW_PARAM_QUERY may reduce configuration
 844  *   space making it possible to iteratively get the final stream configuration,
 845  *   used in XENSND_OP_OPEN request.
 846  *
 847  *   See response format for this request.
 848  *
 849  *         0                1                 2               3        octet
 850  * +----------------+----------------+----------------+----------------+
 851  * |               id                | _HW_PARAM_QUERY|    reserved    | 4
 852  * +----------------+----------------+----------------+----------------+
 853  * |                             reserved                              | 8
 854  * +----------------+----------------+----------------+----------------+
 855  * |                     formats mask low 32-bit                       | 12
 856  * +----------------+----------------+----------------+----------------+
 857  * |                     formats mask high 32-bit                      | 16
 858  * +----------------+----------------+----------------+----------------+
 859  * |                              min rate                             | 20
 860  * +----------------+----------------+----------------+----------------+
 861  * |                              max rate                             | 24
 862  * +----------------+----------------+----------------+----------------+
 863  * |                            min channels                           | 28
 864  * +----------------+----------------+----------------+----------------+
 865  * |                            max channels                           | 32
 866  * +----------------+----------------+----------------+----------------+
 867  * |                         min buffer frames                         | 36
 868  * +----------------+----------------+----------------+----------------+
 869  * |                         max buffer frames                         | 40
 870  * +----------------+----------------+----------------+----------------+
 871  * |                         min period frames                         | 44
 872  * +----------------+----------------+----------------+----------------+
 873  * |                         max period frames                         | 48
 874  * +----------------+----------------+----------------+----------------+
 875  * |                             reserved                              | 52
 876  * +----------------+----------------+----------------+----------------+
 877  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 878  * +----------------+----------------+----------------+----------------+
 879  * |                             reserved                              | 64
 880  * +----------------+----------------+----------------+----------------+
 881  *
 882  * formats - uint64_t, bit mask representing values of the parameter
 883  *     made as bitwise OR of (1 << XENSND_PCM_FORMAT_XXX) values
 884  *
 885  * For interval parameters:
 886  *   min - uint32_t, minimum value of the parameter
 887  *   max - uint32_t, maximum value of the parameter
 888  *
 889  * Frame is defined as a product of the number of channels by the
 890  * number of octets per one sample.
 891  */
 892
 893 struct xensnd_query_hw_param {
 894         uint64_t formats;
 895         struct {
 896                 uint32_t min;
 897                 uint32_t max;
 898         } rates;
 899         struct {
 900                 uint32_t min;
 901                 uint32_t max;
 902         } channels;
 903         struct {
 904                 uint32_t min;
 905                 uint32_t max;
 906         } buffer;
 907         struct {
 908                 uint32_t min;
 909                 uint32_t max;
 910         } period;
 911 };
 912
 913 /*
 914  *---------------------------------- Responses --------------------------------
 915  *
 916  * All response packets have the same length (64 octets)
 917  *
 918  * All response packets have common header:
 919  *         0                1                 2               3        octet
 920  * +----------------+----------------+----------------+----------------+
 921  * |               id                |    operation   |    reserved    | 4
 922  * +----------------+----------------+----------------+----------------+
 923  * |                              status                               | 8
 924  * +----------------+----------------+----------------+----------------+
 925  *
 926  * id - uint16_t, copied from the request
 927  * operation - uint8_t, XENSND_OP_* - copied from request
 928  * status - int32_t, response status, zero on success and -XEN_EXX on failure
 929  *
 930  *
 931  * HW parameter query response - response for XENSND_OP_HW_PARAM_QUERY:
 932  *         0                1                 2               3        octet
 933  * +----------------+----------------+----------------+----------------+
 934  * |               id                |    operation   |    reserved    | 4
 935  * +----------------+----------------+----------------+----------------+
 936  * |                              status                               | 8
 937  * +----------------+----------------+----------------+----------------+
 938  * |                     formats mask low 32-bit                       | 12
 939  * +----------------+----------------+----------------+----------------+
 940  * |                     formats mask high 32-bit                      | 16
 941  * +----------------+----------------+----------------+----------------+
 942  * |                              min rate                             | 20
 943  * +----------------+----------------+----------------+----------------+
 944  * |                              max rate                             | 24
 945  * +----------------+----------------+----------------+----------------+
 946  * |                            min channels                           | 28
 947  * +----------------+----------------+----------------+----------------+
 948  * |                            max channels                           | 32
 949  * +----------------+----------------+----------------+----------------+
 950  * |                         min buffer frames                         | 36
 951  * +----------------+----------------+----------------+----------------+
 952  * |                         max buffer frames                         | 40
 953  * +----------------+----------------+----------------+----------------+
 954  * |                         min period frames                         | 44
 955  * +----------------+----------------+----------------+----------------+
 956  * |                         max period frames                         | 48
 957  * +----------------+----------------+----------------+----------------+
 958  * |                             reserved                              | 52
 959  * +----------------+----------------+----------------+----------------+
 960  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 961  * +----------------+----------------+----------------+----------------+
 962  * |                             reserved                              | 64
 963  * +----------------+----------------+----------------+----------------+
 964  *
 965  * Meaning of the values in this response is the same as for
 966  * XENSND_OP_HW_PARAM_QUERY request.
 967  */
 968
 969 /*
 970  *----------------------------------- Events ----------------------------------
 971  *
 972  * Events are sent via shared page allocated by the front and propagated by
 973  *   evt-event-channel/evt-ring-ref XenStore entries
 974  * All event packets have the same length (64 octets)
 975  * All event packets have common header:
 976  *         0                1                 2               3        octet
 977  * +----------------+----------------+----------------+----------------+
 978  * |               id                |      type      |   reserved     | 4
 979  * +----------------+----------------+----------------+----------------+
 980  * |                             reserved                              | 8
 981  * +----------------+----------------+----------------+----------------+
 982  *
 983  * id - uint16_t, event id, may be used by front
 984  * type - uint8_t, type of the event
 985  *
 986  *
 987  * Current stream position - event from back to front when stream's
 988  *   playback/capture position has advanced:
 989  *         0                1                 2               3        octet
 990  * +----------------+----------------+----------------+----------------+
 991  * |               id                |   _EVT_CUR_POS |   reserved     | 4
 992  * +----------------+----------------+----------------+----------------+
 993  * |                             reserved                              | 8
 994  * +----------------+----------------+----------------+----------------+
 995  * |                         position low 32-bit                       | 12
 996  * +----------------+----------------+----------------+----------------+
 997  * |                         position high 32-bit                      | 16
 998  * +----------------+----------------+----------------+----------------+
 999  * |                             reserved                              | 20
1000  * +----------------+----------------+----------------+----------------+
1001  * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
1002  * +----------------+----------------+----------------+----------------+
1003  * |                             reserved                              | 64
1004  * +----------------+----------------+----------------+----------------+
1005  *
1006  * position - current value of stream's playback/capture position, octets
1007  *
1008  */
1009
1010 struct xensnd_cur_pos_evt {
1011         uint64_t position;
1012 };
1013
1014 struct xensnd_req {
1015         uint16_t id;
1016         uint8_t operation;
1017         uint8_t reserved[5];
1018         union {
1019                 struct xensnd_open_req open;
1020                 struct xensnd_rw_req rw;
1021                 struct xensnd_trigger_req trigger;
1022                 struct xensnd_query_hw_param hw_param;
1023                 uint8_t reserved[56];
1024         } op;
1025 };
1026
1027 struct xensnd_resp {
1028         uint16_t id;
1029         uint8_t operation;
1030         uint8_t reserved;
1031         int32_t status;
1032         union {
1033                 struct xensnd_query_hw_param hw_param;
1034                 uint8_t reserved1[56];
1035         } resp;
1036 };
1037
1038 struct xensnd_evt {
1039         uint16_t id;
1040         uint8_t type;
1041         uint8_t reserved[5];
1042         union {
1043                 struct xensnd_cur_pos_evt cur_pos;
1044                 uint8_t reserved[56];
1045         } op;
1046 };
1047
1048 DEFINE_RING_TYPES(xen_sndif, struct xensnd_req, struct xensnd_resp);
1049
1050 /*
1051  ******************************************************************************
1052  *                        Back to front events delivery
1053  ******************************************************************************
1054  * In order to deliver asynchronous events from back to front a shared page is
1055  * allocated by front and its granted reference propagated to back via
1056  * XenStore entries (evt-ring-ref/evt-event-channel).
1057  * This page has a common header used by both front and back to synchronize
1058  * access and control event's ring buffer, while back being a producer of the
1059  * events and front being a consumer. The rest of the page after the header
1060  * is used for event packets.
1061  *
1062  * Upon reception of an event(s) front may confirm its reception
1063  * for either each event, group of events or none.
1064  */
1065
1066 struct xensnd_event_page {
1067         uint32_t in_cons;
1068         uint32_t in_prod;
1069         uint8_t reserved[56];
1070 };
1071
1072 #define XENSND_EVENT_PAGE_SIZE XEN_PAGE_SIZE
1073 #define XENSND_IN_RING_OFFS (sizeof(struct xensnd_event_page))
1074 #define XENSND_IN_RING_SIZE (XENSND_EVENT_PAGE_SIZE - XENSND_IN_RING_OFFS)
1075 #define XENSND_IN_RING_LEN (XENSND_IN_RING_SIZE / sizeof(struct xensnd_evt))
1076 #define XENSND_IN_RING(page) \
1077         ((struct xensnd_evt *)((char *)(page) + XENSND_IN_RING_OFFS))
1078 #define XENSND_IN_RING_REF(page, idx) \
1079         (XENSND_IN_RING((page))[(idx) % XENSND_IN_RING_LEN])
1080
1081 #endif /* __XEN_PUBLIC_IO_SNDIF_H__ */