path: root/include/xen/interface/io/sndif.h

/******************************************************************************
 * sndif.h
 *
 * Unified sound-device I/O interface for Xen guest OSes.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * Copyright (C) 2013-2015 GlobalLogic Inc.
 * Copyright (C) 2016-2017 EPAM Systems Inc.
 *
 * Authors: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
 *          Oleksandr Grytsov <oleksandr_grytsov@epam.com>
 *          Oleksandr Dmytryshyn <oleksandr.dmytryshyn@globallogic.com>
 *          Iurii Konovalenko <iurii.konovalenko@globallogic.com>
 */

#ifndef __XEN_PUBLIC_IO_SNDIF_H__
#define __XEN_PUBLIC_IO_SNDIF_H__

#include "ring.h"
#include "../grant_table.h"

/*
 ******************************************************************************
 *                  Feature and Parameter Negotiation
 ******************************************************************************
 *
 * Front->back notifications: when enqueuing a new request, sending a
 * notification can be made conditional on xensnd_req (i.e., the generic
 * hold-off mechanism provided by the ring macros). Backends must set
 * xensnd_req appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
 *
 * Back->front notifications: when enqueuing a new response, sending a
 * notification can be made conditional on xensnd_resp (i.e., the generic
 * hold-off mechanism provided by the ring macros). Frontends must set
 * xensnd_resp appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
 *
 * The two halves of a para-virtual sound card driver utilize nodes within
 * XenStore to communicate capabilities and to negotiate operating parameters.
 * This section enumerates these nodes which reside in the respective front and
 * backend portions of XenStore, following the XenBus convention.
 *
 * All data in XenStore is stored as strings. Nodes specifying numeric
 * values are encoded in decimal. Integer value ranges listed below are
 * expressed as fixed sized integer types capable of storing the conversion
 * of a properly formated node string, without loss of information.
 *
 ******************************************************************************
 *                        Example configuration
 ******************************************************************************
 *
 * Note: depending on the use-case backend can expose more sound cards and
 * PCM devices/streams than the underlying HW physically has by employing
 * SW mixers, configuring virtual sound streams, channels etc.
 *
 * This is an example of backend and frontend configuration:
 *
 *--------------------------------- Backend -----------------------------------
 *
 * /local/domain/0/backend/vsnd/1/0/frontend-id = "1"
 * /local/domain/0/backend/vsnd/1/0/frontend = "/local/domain/1/device/vsnd/0"
 * /local/domain/0/backend/vsnd/1/0/state = "4"
 * /local/domain/0/backend/vsnd/1/0/versions = "1,2"
 *
 *--------------------------------- Frontend ----------------------------------
 *
 * /local/domain/1/device/vsnd/0/backend-id = "0"
 * /local/domain/1/device/vsnd/0/backend = "/local/domain/0/backend/vsnd/1/0"
 * /local/domain/1/device/vsnd/0/state = "4"
 * /local/domain/1/device/vsnd/0/version = "1"
 *
 *----------------------------- Card configuration ----------------------------
 *
 * /local/domain/1/device/vsnd/0/short-name = "Card short name"
 * /local/domain/1/device/vsnd/0/long-name = "Card long name"
 * /local/domain/1/device/vsnd/0/sample-rates = "8000,32000,44100,48000,96000"
 * /local/domain/1/device/vsnd/0/sample-formats = "s8,u8,s16_le,s16_be"
 * /local/domain/1/device/vsnd/0/buffer-size = "262144"
 *
 *------------------------------- PCM device 0 --------------------------------
 *
 * /local/domain/1/device/vsnd/0/0/name = "General analog"
 * /local/domain/1/device/vsnd/0/0/channels-max = "5"
 *
 *----------------------------- Stream 0, playback ----------------------------
 *
 * /local/domain/1/device/vsnd/0/0/0/type = "p"
 * /local/domain/1/device/vsnd/0/0/0/sample-formats = "s8,u8"
 * /local/domain/1/device/vsnd/0/0/0/unique-id = "0"
 *
 * /local/domain/1/device/vsnd/0/0/0/ring-ref = "386"
 * /local/domain/1/device/vsnd/0/0/0/event-channel = "15"
 *
 *------------------------------ Stream 1, capture ----------------------------
 *
 * /local/domain/1/device/vsnd/0/0/1/type = "c"
 * /local/domain/1/device/vsnd/0/0/1/channels-max = "2"
 * /local/domain/1/device/vsnd/0/0/1/unique-id = "1"
 *
 * /local/domain/1/device/vsnd/0/0/1/ring-ref = "384"
 * /local/domain/1/device/vsnd/0/0/1/event-channel = "13"
 *
 *------------------------------- PCM device 1 --------------------------------
 *
 * /local/domain/1/device/vsnd/0/1/name = "HDMI-0"
 * /local/domain/1/device/vsnd/0/1/sample-rates = "8000,32000,44100"
 *
 *------------------------------ Stream 0, capture ----------------------------
 *
 * /local/domain/1/device/vsnd/0/1/0/type = "c"
 * /local/domain/1/device/vsnd/0/1/0/unique-id = "2"
 *
 * /local/domain/1/device/vsnd/0/1/0/ring-ref = "387"
 * /local/domain/1/device/vsnd/0/1/0/event-channel = "151"
 *
 *------------------------------- PCM device 2 --------------------------------
 *
 * /local/domain/1/device/vsnd/0/2/name = "SPDIF"
 *
 *----------------------------- Stream 0, playback ----------------------------
 *
 * /local/domain/1/device/vsnd/0/2/0/type = "p"
 * /local/domain/1/device/vsnd/0/2/0/unique-id = "3"
 *
 * /local/domain/1/device/vsnd/0/2/0/ring-ref = "389"
 * /local/domain/1/device/vsnd/0/2/0/event-channel = "152"
 *
 ******************************************************************************
 *                            Backend XenBus Nodes
 ******************************************************************************
 *
 *----------------------------- Protocol version ------------------------------
 *
 * versions
 *      Values:         <string>
 *
 *      List of XENSND_LIST_SEPARATOR separated protocol versions supported
 *      by the backend. For example "1,2,3".
 *
 ******************************************************************************
 *                            Frontend XenBus Nodes
 ******************************************************************************
 *
 *-------------------------------- Addressing ---------------------------------
 *
 * dom-id
 *      Values:         <uint16_t>
 *
 *      Domain identifier.
 *
 * dev-id
 *      Values:         <uint16_t>
 *
 *      Device identifier.
 *
 * pcm-dev-idx
 *      Values:         <uint8_t>
 *
 *      Zero based contigous index of the PCM device.
 *
 * stream-idx
 *      Values:         <uint8_t>
 *
 *      Zero based contigous index of the stream of the PCM device.
 *
 * The following pattern is used for addressing:
 *   /local/domain/<dom-id>/device/vsnd/<dev-id>/<pcm-dev-idx>/<stream-idx>/...
 *
 *----------------------------- Protocol version ------------------------------
 *
 * version
 *      Values:         <string>
 *
 *      Protocol version, chosen among the ones supported by the backend.
 *
 *------------------------------- PCM settings --------------------------------
 *
 * Every virtualized sound frontend has a set of PCM devices and streams, each
 * could be individually configured. Part of the PCM configuration can be
 * defined at higher level of the hierarchy and be fully or partially re-used
 * by the underlying layers. These configuration values are:
 *  o number of channels (min/max)
 *  o supported sample rates
 *  o supported sample formats.
 * E.g. one can define these values for the whole card, device or stream.
 * Every underlying layer in turn can re-define some or all of them to better
 * fit its needs. For example, card may define number of channels to be
 * in [1; 8] range, and some particular stream may be limited to [1; 2] only.
 * The rule is that the underlying layer must be a subset of the upper layer
 * range.
 *
 * channels-min
 *      Values:         <uint8_t>
 *
 *      The minimum amount of channels that is supported, [1; channels-max].
 *      Optional, if not set or omitted a value of 1 is used.
 *
 * channels-max
 *      Values:         <uint8_t>
 *
 *      The maximum amount of channels that is supported.
 *      Must be at least <channels-min>.
 *
 * sample-rates
 *      Values:         <list of uint32_t>
 *
 *      List of supported sample rates separated by XENSND_LIST_SEPARATOR.
 *      Sample rates are expressed as a list of decimal values w/o any
 *      ordering requirement.
 *
 * sample-formats
 *      Values:         <list of XENSND_PCM_FORMAT_XXX_STR>
 *
 *      List of supported sample formats separated by XENSND_LIST_SEPARATOR.
 *      Items must not exceed XENSND_SAMPLE_FORMAT_MAX_LEN length.
 *
 * buffer-size
 *      Values:         <uint32_t>
 *
 *      The maximum size in octets of the buffer to allocate per stream.
 *
 *----------------------- Virtual sound card settings -------------------------
 * short-name
 *      Values:         <char[32]>
 *
 *      Short name of the virtual sound card. Optional.
 *
 * long-name
 *      Values:         <char[80]>
 *
 *      Long name of the virtual sound card. Optional.
 *
 *----------------------------- Device settings -------------------------------
 * name
 *      Values:         <char[80]>
 *
 *      Name of the sound device within the virtual sound card. Optional.
 *
 *----------------------------- Stream settings -------------------------------
 *
 * type
 *      Values:         "p", "c"
 *
 *      Stream type: "p" - playback stream, "c" - capture stream
 *
 *      If both capture and playback are needed then two streams need to be
 *      defined under the same device.
 *
 * unique-id
 *      Values:         <uint32_t>
 *
 *      After stream initialization it is assigned a unique ID (within the front
 *      driver), so every stream of the frontend can be identified by the
 *      backend by this ID. This is not equal to stream-idx as the later is
 *      zero based within the device, but this index is contigous within the
 *      driver.
 *
 *-------------------- Stream Request Transport Parameters --------------------
 *
 * event-channel
 *      Values:         <uint32_t>
 *
 *      The identifier of the Xen event channel used to signal activity
 *      in the ring buffer.
 *
 * ring-ref
 *      Values:         <uint32_t>
 *
 *      The Xen grant reference granting permission for the backend to map
 *      a sole page in a single page sized ring buffer.
 *
 ******************************************************************************
 *                               STATE DIAGRAMS
 ******************************************************************************
 *
 * Tool stack creates front and back state nodes with initial state
 * XenbusStateInitialising.
 * Tool stack creates and sets up frontend sound configuration nodes per domain.
 *
 * Front                                Back
 * =================================    =====================================
 * XenbusStateInitialising              XenbusStateInitialising
 *                                       o Query backend device identification
 *                                         data.
 *                                       o Open and validate backend device.
 *                                                      |
 *                                                      |
 *                                                      V
 *                                      XenbusStateInitWait
 *
 * o Query frontend configuration
 * o Allocate and initialize
 *   event channels per configured
 *   playback/capture stream.
 * o Publish transport parameters
 *   that will be in effect during
 *   this connection.
 *              |
 *              |
 *              V
 * XenbusStateInitialised
 *
 *                                       o Query frontend transport parameters.
 *                                       o Connect to the event channels.
 *                                                      |
 *                                                      |
 *                                                      V
 *                                      XenbusStateConnected
 *
 *  o Create and initialize OS
 *    virtual sound device instances
 *    as per configuration.
 *              |
 *              |
 *              V
 * XenbusStateConnected
 *
 *                                      XenbusStateUnknown
 *                                      XenbusStateClosed
 *                                      XenbusStateClosing
 * o Remove virtual sound device
 * o Remove event channels
 *              |
 *              |
 *              V
 * XenbusStateClosed
 *
 *------------------------------- Recovery flow -------------------------------
 *
 * In case of frontend unrecoverable errors backend handles that as
 * if frontend goes into the XenbusStateClosed state.
 *
 * In case of backend unrecoverable errors frontend tries removing
 * the virtualized device. If this is possible at the moment of error,
 * then frontend goes into the XenbusStateInitialising state and is ready for
 * new connection with backend. If the virtualized device is still in use and
 * cannot be removed, then frontend goes into the XenbusStateReconfiguring state
 * until either the virtualized device removed or backend initiates a new
 * connection. On the virtualized device removal frontend goes into the
 * XenbusStateInitialising state.
 *
 * Note on XenbusStateReconfiguring state of the frontend: if backend has
 * unrecoverable errors then frontend cannot send requests to the backend
 * and thus cannot provide functionality of the virtualized device anymore.
 * After backend is back to normal the virtualized device may still hold some
 * state: configuration in use, allocated buffers, client application state etc.
 * So, in most cases, this will require frontend to implement complex recovery
 * reconnect logic. Instead, by going into XenbusStateReconfiguring state,
 * frontend will make sure no new clients of the virtualized device are
 * accepted, allow existing client(s) to exit gracefully by signaling error
 * state etc.
 * Once all the clients are gone frontend can reinitialize the virtualized
 * device and get into XenbusStateInitialising state again signaling the
 * backend that a new connection can be made.
 *
 * There are multiple conditions possible under which frontend will go from
 * XenbusStateReconfiguring into XenbusStateInitialising, some of them are OS
 * specific. For example:
 * 1. The underlying OS framework may provide callbacks to signal that the last
 *    client of the virtualized device has gone and the device can be removed
 * 2. Frontend can schedule a deferred work (timer/tasklet/workqueue)
 *    to periodically check if this is the right time to re-try removal of
 *    the virtualized device.
 * 3. By any other means.
 *
 ******************************************************************************
 *                             PCM FORMATS
 ******************************************************************************
 *
 * XENSND_PCM_FORMAT_<format>[_<endian>]
 *
 * format: <S/U/F><bits> or <name>
 *     S - signed, U - unsigned, F - float
 *     bits - 8, 16, 24, 32
 *     name - MU_LAW, GSM, etc.
 *
 * endian: <LE/BE>, may be absent
 *     LE - Little endian, BE - Big endian
 */
#define XENSND_PCM_FORMAT_S8		0
#define XENSND_PCM_FORMAT_U8		1
#define XENSND_PCM_FORMAT_S16_LE	2
#define XENSND_PCM_FORMAT_S16_BE	3
#define XENSND_PCM_FORMAT_U16_LE	4
#define XENSND_PCM_FORMAT_U16_BE	5
#define XENSND_PCM_FORMAT_S24_LE	6
#define XENSND_PCM_FORMAT_S24_BE	7
#define XENSND_PCM_FORMAT_U24_LE	8
#define XENSND_PCM_FORMAT_U24_BE	9
#define XENSND_PCM_FORMAT_S32_LE	10
#define XENSND_PCM_FORMAT_S32_BE	11
#define XENSND_PCM_FORMAT_U32_LE	12
#define XENSND_PCM_FORMAT_U32_BE	13
#define XENSND_PCM_FORMAT_F32_LE	14 /* 4-byte float, IEEE-754 32-bit, */
#define XENSND_PCM_FORMAT_F32_BE	15 /* range -1.0 to 1.0              */
#define XENSND_PCM_FORMAT_F64_LE	16 /* 8-byte float, IEEE-754 64-bit, */
#define XENSND_PCM_FORMAT_F64_BE	17 /* range -1.0 to 1.0              */
#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE 18
#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE 19
#define XENSND_PCM_FORMAT_MU_LAW	20
#define XENSND_PCM_FORMAT_A_LAW		21
#define XENSND_PCM_FORMAT_IMA_ADPCM	22
#define XENSND_PCM_FORMAT_MPEG		23
#define XENSND_PCM_FORMAT_GSM		24

/*
 ******************************************************************************
 *                             REQUEST CODES
 ******************************************************************************
 */
#define XENSND_OP_OPEN			0
#define XENSND_OP_CLOSE			1
#define XENSND_OP_READ			2
#define XENSND_OP_WRITE			3
#define XENSND_OP_SET_VOLUME		4
#define XENSND_OP_GET_VOLUME		5
#define XENSND_OP_MUTE			6
#define XENSND_OP_UNMUTE		7

/*
 ******************************************************************************
 *               XENSTORE FIELD AND PATH NAME STRINGS, HELPERS
 ******************************************************************************
 */
#define XENSND_DRIVER_NAME		"vsnd"

#define XENSND_LIST_SEPARATOR		","
/* Field names */
#define XENSND_FIELD_BE_VERSIONS	"versions"
#define XENSND_FIELD_FE_VERSION		"version"
#define XENSND_FIELD_VCARD_SHORT_NAME	"short-name"
#define XENSND_FIELD_VCARD_LONG_NAME	"long-name"
#define XENSND_FIELD_RING_REF		"ring-ref"
#define XENSND_FIELD_EVT_CHNL		"event-channel"
#define XENSND_FIELD_DEVICE_NAME	"name"
#define XENSND_FIELD_TYPE		"type"
#define XENSND_FIELD_STREAM_UNIQUE_ID	"unique-id"
#define XENSND_FIELD_CHANNELS_MIN	"channels-min"
#define XENSND_FIELD_CHANNELS_MAX	"channels-max"
#define XENSND_FIELD_SAMPLE_RATES	"sample-rates"
#define XENSND_FIELD_SAMPLE_FORMATS	"sample-formats"
#define XENSND_FIELD_BUFFER_SIZE	"buffer-size"

/* Stream type field values. */
#define XENSND_STREAM_TYPE_PLAYBACK	"p"
#define XENSND_STREAM_TYPE_CAPTURE	"c"
/* Sample rate max string length */
#define XENSND_SAMPLE_RATE_MAX_LEN	11
/* Sample format field values */
#define XENSND_SAMPLE_FORMAT_MAX_LEN	24

#define XENSND_PCM_FORMAT_S8_STR	"s8"
#define XENSND_PCM_FORMAT_U8_STR	"u8"
#define XENSND_PCM_FORMAT_S16_LE_STR	"s16_le"
#define XENSND_PCM_FORMAT_S16_BE_STR	"s16_be"
#define XENSND_PCM_FORMAT_U16_LE_STR	"u16_le"
#define XENSND_PCM_FORMAT_U16_BE_STR	"u16_be"
#define XENSND_PCM_FORMAT_S24_LE_STR	"s24_le"
#define XENSND_PCM_FORMAT_S24_BE_STR	"s24_be"
#define XENSND_PCM_FORMAT_U24_LE_STR	"u24_le"
#define XENSND_PCM_FORMAT_U24_BE_STR	"u24_be"
#define XENSND_PCM_FORMAT_S32_LE_STR	"s32_le"
#define XENSND_PCM_FORMAT_S32_BE_STR	"s32_be"
#define XENSND_PCM_FORMAT_U32_LE_STR	"u32_le"
#define XENSND_PCM_FORMAT_U32_BE_STR	"u32_be"
#define XENSND_PCM_FORMAT_F32_LE_STR	"float_le"
#define XENSND_PCM_FORMAT_F32_BE_STR	"float_be"
#define XENSND_PCM_FORMAT_F64_LE_STR	"float64_le"
#define XENSND_PCM_FORMAT_F64_BE_STR	"float64_be"
#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_LE_STR "iec958_subframe_le"
#define XENSND_PCM_FORMAT_IEC958_SUBFRAME_BE_STR "iec958_subframe_be"
#define XENSND_PCM_FORMAT_MU_LAW_STR	"mu_law"
#define XENSND_PCM_FORMAT_A_LAW_STR	"a_law"
#define XENSND_PCM_FORMAT_IMA_ADPCM_STR	"ima_adpcm"
#define XENSND_PCM_FORMAT_MPEG_STR	"mpeg"
#define XENSND_PCM_FORMAT_GSM_STR	"gsm"


/*
 ******************************************************************************
 *                          STATUS RETURN CODES
 ******************************************************************************
 *
 * Status return code is zero on success and -XEN_EXX on failure.
 *
 ******************************************************************************
 *                              Assumptions
 ******************************************************************************
 * o usage of grant reference 0 as invalid grant reference:
 *   grant reference 0 is valid, but never exposed to a PV driver,
 *   because of the fact it is already in use/reserved by the PV console.
 * o all references in this document to page sizes must be treated
 *   as pages of size XEN_PAGE_SIZE unless otherwise noted.
 *
 ******************************************************************************
 *       Description of the protocol between frontend and backend driver
 ******************************************************************************
 *
 * The two halves of a Para-virtual sound driver communicate with
 * each other using shared pages and event channels.
 * Shared page contains a ring with request/response packets.
 *
 * Packets, used for input/output operations, e.g. read/write, set/get volume,
 * etc., provide offset/length fields in order to allow asynchronous protocol
 * operation with buffer space sharing: part of the buffer allocated at
 * XENSND_OP_OPEN can be used for audio samples and part, for example,
 * for volume control.
 *
 * All reserved fields in the structures below must be 0.
 *
 *---------------------------------- Requests ---------------------------------
 *
 * All request packets have the same length (32 octets)
 * All request packets have common header:
 *         0                1                 2               3        octet
 * +----------------+----------------+----------------+----------------+
 * |               id                |    operation   |    reserved    | 4
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 8
 * +----------------+----------------+----------------+----------------+
 *   id - uint16_t, private guest value, echoed in response
 *   operation - uint8_t, operation code, XENSND_OP_???
 *
 * For all packets which use offset and length:
 *   offset - uint32_t, read or write data offset within the shared buffer,
 *     passed with XENSND_OP_OPEN request, octets,
 *     [0; XENSND_OP_OPEN.buffer_sz - 1].
 *   length - uint32_t, read or write data length, octets
 *
 * Request open - open a PCM stream for playback or capture:
 *
 *         0                1                 2               3        octet
 * +----------------+----------------+----------------+----------------+
 * |               id                | XENSND_OP_OPEN |    reserved    | 4
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 8
 * +----------------+----------------+----------------+----------------+
 * |                             pcm_rate                              | 12
 * +----------------+----------------+----------------+----------------+
 * |  pcm_format    |  pcm_channels  |             reserved            | 16
 * +----------------+----------------+----------------+----------------+
 * |                             buffer_sz                             | 20
 * +----------------+----------------+----------------+----------------+
 * |                           gref_directory                          | 24
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 28
 * +----------------+----------------+----------------+----------------+
 * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 32
 * +----------------+----------------+----------------+----------------+
 *
 * pcm_rate - uint32_t, stream data rate, Hz
 * pcm_format - uint8_t, XENSND_PCM_FORMAT_XXX value
 * pcm_channels - uint8_t, number of channels of this stream,
 *   [channels-min; channels-max]
 * buffer_sz - uint32_t, buffer size to be allocated, octets
 * gref_directory - grant_ref_t, a reference to the first shared page
 *   describing shared buffer references. At least one page exists. If shared
 *   buffer size  (buffer_sz) exceeds what can be addressed by this single page,
 *   then reference to the next page must be supplied (see gref_dir_next_page
 *   below)
 */

struct xensnd_open_req {
	uint32_t pcm_rate;
	uint8_t pcm_format;
	uint8_t pcm_channels;
	uint16_t reserved;
	uint32_t buffer_sz;
	grant_ref_t gref_directory;
};

/*
 * Shared page for XENSND_OP_OPEN buffer descriptor (gref_directory in the
 *   request) employs a list of pages, describing all pages of the shared data
 *   buffer:
 *         0                1                 2               3        octet
 * +----------------+----------------+----------------+----------------+
 * |                        gref_dir_next_page                         | 4
 * +----------------+----------------+----------------+----------------+
 * |                              gref[0]                              | 8
 * +----------------+----------------+----------------+----------------+
 * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 * +----------------+----------------+----------------+----------------+
 * |                              gref[i]                              | i*4+8
 * +----------------+----------------+----------------+----------------+
 * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 * +----------------+----------------+----------------+----------------+
 * |                             gref[N - 1]                           | N*4+8
 * +----------------+----------------+----------------+----------------+
 *
 * gref_dir_next_page - grant_ref_t, reference to the next page describing
 *   page directory. Must be 0 if there are no more pages in the list.
 * gref[i] - grant_ref_t, reference to a shared page of the buffer
 *   allocated at XENSND_OP_OPEN
 *
 * Number of grant_ref_t entries in the whole page directory is not
 * passed, but instead can be calculated as:
 *   num_grefs_total = (XENSND_OP_OPEN.buffer_sz + XEN_PAGE_SIZE - 1) /
 *       XEN_PAGE_SIZE
 */

struct xensnd_page_directory {
	grant_ref_t gref_dir_next_page;
	grant_ref_t gref[1]; /* Variable length */
};

/*
 *  Request close - close an opened pcm stream:
 *         0                1                 2               3        octet
 * +----------------+----------------+----------------+----------------+
 * |               id                | XENSND_OP_CLOSE|    reserved    | 4
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 8
 * +----------------+----------------+----------------+----------------+
 * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 32
 * +----------------+----------------+----------------+----------------+
 *
 * Request read/write - used for read (for capture) or write (for playback):
 *         0                1                 2               3        octet
 * +----------------+----------------+----------------+----------------+
 * |               id                |   operation    |    reserved    | 4
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 8
 * +----------------+----------------+----------------+----------------+
 * |                              offset                               | 12
 * +----------------+----------------+----------------+----------------+
 * |                              length                               | 16
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 20
 * +----------------+----------------+----------------+----------------+
 * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 32
 * +----------------+----------------+----------------+----------------+
 *
 * operation - XENSND_OP_READ for read or XENSND_OP_WRITE for write
 */

struct xensnd_rw_req {
	uint32_t offset;
	uint32_t length;
};

/*
 * Request set/get volume - set/get channels' volume of the stream given:
 *         0                1                 2               3        octet
 * +----------------+----------------+----------------+----------------+
 * |               id                |   operation    |    reserved    | 4
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 8
 * +----------------+----------------+----------------+----------------+
 * |                              offset                               | 12
 * +----------------+----------------+----------------+----------------+
 * |                              length                               | 16
 * +----------------+----------------+----------------+----------------+
 * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 32
 * +----------------+----------------+----------------+----------------+
 *
 * operation - XENSND_OP_SET_VOLUME for volume set
 *   or XENSND_OP_GET_VOLUME for volume get
 * Buffer passed with XENSND_OP_OPEN is used to exchange volume
 * values:
 *
 *         0                1                 2               3        octet
 * +----------------+----------------+----------------+----------------+
 * |                             channel[0]                            | 4
 * +----------------+----------------+----------------+----------------+
 * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 * +----------------+----------------+----------------+----------------+
 * |                             channel[i]                            | i*4
 * +----------------+----------------+----------------+----------------+
 * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 * +----------------+----------------+----------------+----------------+
 * |                           channel[N - 1]                          | (N-1)*4
 * +----------------+----------------+----------------+----------------+
 *
 * N = XENSND_OP_OPEN.pcm_channels
 * i - uint8_t, index of a channel
 * channel[i] - sint32_t, volume of i-th channel
 * Volume is expressed as a signed value in steps of 0.001 dB,
 * while 0 being 0 dB.
 *
 * Request mute/unmute - mute/unmute stream:
 *         0                1                 2               3        octet
 * +----------------+----------------+----------------+----------------+
 * |               id                |   operation    |    reserved    | 4
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 8
 * +----------------+----------------+----------------+----------------+
 * |                              offset                               | 12
 * +----------------+----------------+----------------+----------------+
 * |                              length                               | 16
 * +----------------+----------------+----------------+----------------+
 * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 32
 * +----------------+----------------+----------------+----------------+
 *
 * operation - XENSND_OP_MUTE for mute or XENSND_OP_UNMUTE for unmute
 * Buffer passed with XENSND_OP_OPEN is used to exchange mute/unmute
 * values:
 *
 *                                   0                                 octet
 * +----------------+----------------+----------------+----------------+
 * |                             channel[0]                            | 4
 * +----------------+----------------+----------------+----------------+
 * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 * +----------------+----------------+----------------+----------------+
 * |                             channel[i]                            | i*4
 * +----------------+----------------+----------------+----------------+
 * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 * +----------------+----------------+----------------+----------------+
 * |                           channel[N - 1]                          | (N-1)*4
 * +----------------+----------------+----------------+----------------+
 *
 * N = XENSND_OP_OPEN.pcm_channels
 * i - uint8_t, index of a channel
 * channel[i] - uint8_t, non-zero if i-th channel needs to be muted/unmuted
 *
 *------------------------------------ N.B. -----------------------------------
 *
 * The 'struct xensnd_rw_req' is also used for XENSND_OP_SET_VOLUME,
 * XENSND_OP_GET_VOLUME, XENSND_OP_MUTE, XENSND_OP_UNMUTE.
 */

/*
 *---------------------------------- Responses --------------------------------
 *
 * All response packets have the same length (32 octets)
 *
 * Response for all requests:
 *         0                1                 2               3        octet
 * +----------------+----------------+----------------+----------------+
 * |               id                |    operation   |    reserved    | 4
 * +----------------+----------------+----------------+----------------+
 * |                              status                               | 8
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 12
 * +----------------+----------------+----------------+----------------+
 * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
 * +----------------+----------------+----------------+----------------+
 * |                             reserved                              | 32
 * +----------------+----------------+----------------+----------------+
 *
 * id - uint16_t, copied from the request
 * operation - uint8_t, XENSND_OP_* - copied from request
 * status - int32_t, response status, zero on success and -XEN_EXX on failure
 */

struct xensnd_req {
	uint16_t id;
	uint8_t operation;
	uint8_t reserved[5];
	union {
		struct xensnd_open_req open;
		struct xensnd_rw_req rw;
		uint8_t reserved[24];
	} op;
};

struct xensnd_resp {
	uint16_t id;
	uint8_t operation;
	uint8_t reserved;
	int32_t status;
	uint8_t reserved1[24];
};

DEFINE_RING_TYPES(xen_sndif, struct xensnd_req, struct xensnd_resp);

#endif /* __XEN_PUBLIC_IO_SNDIF_H__ */