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+/******************************************************************************
+ * 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 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_XENSND_H__
+#define __XEN_PUBLIC_IO_XENSND_H__
+
+/*
+ * Front->back notifications: When enqueuing a new request, sending a
+ * notification can be made conditional on req_event (i.e., the generic
+ * hold-off mechanism provided by the ring macros). Backends must set
+ * req_event 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 rsp_event (i.e., the generic
+ * hold-off mechanism provided by the ring macros). Frontends must set
+ * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
+ */
+
+/*
+ * Feature and Parameter Negotiation
+ * =================================
+ * The two halves of a Para-virtual sound card driver utilize nodes within the
+ * XenStore to communicate capabilities and to negotiate operating parameters.
+ * This section enumerates these nodes which reside in the respective front and
+ * backend portions of the XenStore, following the XenBus convention.
+ *
+ * All data in the 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.
+ *
+ *****************************************************************************
+ * Backend XenBus Nodes
+ *****************************************************************************
+ *
+ *-------------------------------- Addressing ---------------------------------
+ *
+ * Indices used to address frontends, driver instances, cards,
+ * devices and streams.
+ *
+ * frontend_id
+ * Values: <uint>
+ *
+ * Domain ID of the sound frontend.
+ *
+ * drv_idx
+ * Values: <uint>
+ *
+ * Zero based contiguous index of the virtualized sound driver instance in
+ * this domain. Multiple PV drivers are allowed in the domain
+ * at the same time.
+ *
+ * dev_id
+ * Values: <uint>
+ *
+ * Unique device ID.
+ * Doesn't have to be zero based and/or to be contiguous.
+ *
+ * stream_idx
+ * Values: <uint>
+ *
+ * Zero based contiguous index of the stream of the device.
+ *
+ * Example for the frontend running in domain 5, instance of the driver
+ * in the front is 0 (single or first PV driver), device id 2,
+ * first stream (0):
+ * /local/domain/<frontend_id>/device/vsnd/<drv_idx>/
+ * device/<dev_id>/stream/<stream_idx>/type = "p"
+ * /local/domain/5/device/vsnd/0/device/2/stream/0/type = "p"
+ *
+ *------------------------------- PCM settings --------------------------------
+ *
+ * Every virtualized sound frontend has set of devices and streams, each
+ * is individually configured. Part of the PCM configuration can be defined at
+ * higher level 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 driver, device or stream.
+ * Every underlying layer in turn can re-define some or all of them to better
+ * fit its needs. For example, driver 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.
+ *
+ * Note: if any of the values are not defined then PV driver should use
+ * its default values instead.
+ *
+ * channels-min
+ * Values: <uint>
+ *
+ * The minimum amount of channels that is supported.
+ * Must be at least 1. If not defined then use frontend's default.
+ *
+ * channels-max
+ * Values: <uint>
+ *
+ * The maximum amount of channels that is supported.
+ * Must be at least <channels-min>. If not defined then use frontend's
+ * default.
+ *
+ * sample-rates
+ * Values: <list of uints>
+ *
+ * List of supported sample rates separated by XENSND_LIST_SEPARATOR.
+ * If not defined then use frontend's default. 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.
+ * If not defined then use frontend's default.
+ *
+ * buffer-size
+ * Values: <uint>
+ *
+ * The maximum size in octets of the buffer to allocate per stream.
+ *
+ * Example configuration:
+ *
+ * Driver configuration used by all streams:
+ * /local/domain/5/device/vsnd/0/sample-formats = "s8;u8;s16_le;s16_be"
+ * Stream overrides sample rates supported:
+ * /local/domain/5/device/vsnd/0/device/2/stream/0/sample-rates =
+ * "8000;22050;44100;48000"
+ *
+ *----------------------- 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.
+ *
+ * For example,
+ * /local/domain/5/device/vsnd/0/short-name = "Virtual audio"
+ * /local/domain/5/device/vsnd/0/long-name =
+ * "Virtual audio at center stack"
+ *
+ *----------------------------- Device settings --------------------------------
+ * name
+ * Values: <char[80]>
+ *
+ * Name of the sound device within the virtual sound card. Optional.
+ *
+ * For example,
+ * /local/domain/5/device/vsnd/0/device/0/name = "General analog"
+ *
+ *----------------------------- 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. For example,
+ * /local/domain/5/device/vsnd/0/device/0/stream/0/type = "p"
+ * /local/domain/5/device/vsnd/0/device/0/stream/1/type = "c"
+ *
+ *****************************************************************************
+ * Frontend XenBus Nodes
+ *****************************************************************************
+ *
+ *----------------------- Request Transport Parameters -----------------------
+ *
+ * These are per stream.
+ *
+ * event-channel
+ * Values: <uint>
+ *
+ * The identifier of the Xen event channel used to signal activity
+ * in the ring buffer.
+ *
+ * ring-ref
+ * Values: <uint>
+ *
+ * The Xen grant reference granting permission for the backend to map
+ * a sole page in a single page sized ring buffer.
+ *
+ * index
+ * Values: <uint>
+ *
+ * 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 a device, but this index is contiguous within the
+ * driver.
+ */
+
+/*
+ * STATE DIAGRAMS
+ *
+ *****************************************************************************
+ * Startup *
+ *****************************************************************************
+ *
+ * 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
+ *
+ */
+
+/*
+ * 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 ";"
+/* Path entries */
+#define XENSND_PATH_DEVICE "device"
+#define XENSND_PATH_STREAM "stream"
+/* Field names */
+#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_INDEX "index"
+#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 6
+/* 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.
+ */
+ /* Operation failed for some unspecified reason (e. g. -EIO). */
+#define XENSND_RSP_ERROR (-1)
+ /* Operation completed successfully. */
+#define XENSND_RSP_OKAY 0
+
+/*
+ * Description of the protocol between frontend and backend driver.
+ *
+ * The two halves of a Para-virtual sound driver communicates with
+ * each other using a shared page and an event channel.
+ * Shared page contains a ring with request/response packets.
+ *
+ *
+ * All request packets have the same length (64 octets)
+ *
+ *
+ * Request open - open a PCM stream for playback or capture:
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | id | operation | stream_idx |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | padding |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | pcm_rate |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | pcm_format | pcm_channels | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | gref_directory_start |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * id - uint16_t, private guest value, echoed in response
+ * operation - uint8_t, XENSND_OP_OPEN
+ * stream_idx - uint8_t, index of the stream ("streams_idx" XenStore entry
+ * of the stream)
+ * 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
+ * gref_directory_start - grant_ref_t, a reference to the first shared page
+ * describing shared buffer references. At least one page exists. If shared
+ * buffer size exceeds what can be addressed by this single page, then
+ * reference to the next page must be supplied (gref_dir_next_page below
+ * is not NULL)
+ */
+
+struct xensnd_open_req {
+ uint32_t pcm_rate; /* in Hz */
+ uint8_t pcm_format;
+ uint8_t pcm_channels;
+ uint16_t __reserved0;
+ grant_ref_t gref_directory_start;
+};
+
+/*
+ * 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 |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | num_grefs |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | gref[0] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | gref[1] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | gref[N -1] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * gref_dir_next_page - grant_ref_t, reference to the next page describing
+ * page directory
+ * num_grefs - number of grefs in this page
+ * gref[i] - grant_ref_t, reference to a shared page of the buffer
+ * allocated at XENSND_OP_OPEN
+ */
+
+struct xensnd_page_directory {
+ grant_ref_t gref_dir_next_page;
+ uint32_t num_grefs;
+ grant_ref_t gref[0];
+};
+
+/*
+ * Request close - close an opened pcm stream:
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | id | operation | stream_idx |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | padding |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * id - uint16_t, private guest value, echoed in response
+ * operation - uint8_t, XENSND_OP_CLOSE
+ * stream_idx - uint8_t, index of the stream ("streams_idx" XenStore entry
+ * of the stream)
+ */
+
+struct xensnd_close_req {
+};
+
+/*
+ * Request read/write - used for read (for capture) or write (for playback):
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | id | operation | stream_idx |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | padding |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | offset |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | length |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * id - uint16_t, private guest value, echoed in response
+ * operation - uint8_t, XENSND_OP_READ/XENSND_OP_WRITE
+ * stream_idx - uint8_t, index of the stream ("streams_idx" XenStore entry
+ * of the stream)
+ * offset - uint32_t, read or write data offset within the shared buffer
+ * passed with XENSND_OP_OPEN request
+ * length - uint32_t, read or write data length
+ */
+
+struct xensnd_write_req {
+ uint32_t offset;
+ uint32_t len;
+};
+
+struct xensnd_read_req {
+ uint32_t offset;
+ uint32_t len;
+};
+
+/*
+ * Request set/get volume - set/get channels' volume of the stream given:
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | id | operation | stream_idx |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | padding |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * id - uint16_t, private guest value, echoed in response
+ * operation - uint8_t, XENSND_OP_SET_VOLUME or XENSND_OP_GET_VOLUME
+ * stream_idx - uint8_t, index of the stream ("streams_idx" XenStore entry
+ * of the stream)
+ * Buffer passed with XENSND_OP_OPEN is used to exchange volume
+ * values:
+ *
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | channel[0] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | channel[1] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * channel[XENSND_OP_OPEN.pcm_channels - 1] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * 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.
+ */
+
+struct xensnd_get_vol_req {
+};
+
+struct xensnd_set_vol_req {
+};
+
+/*
+ * Request mute/unmute - mute/unmute stream:
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | id | operation | stream_idx |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | padding |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * id - uint16_t, private guest value, echoed in response
+ * operation - uint8_t, XENSND_OP_MUTE/XENSND_OP_UNMUTE
+ * stream_idx - uint8_t, index of the stream ("streams_idx" XenStore entry
+ * of the stream)
+ * Buffer passed with XENSND_OP_OPEN is used to exchange mute/unmute
+ * values:
+ *
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | channel[0] | channel[1] | channel[2] | channel[3] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | channel[i] | channel[i+1] | channel[i+2] | channel[i+3] |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * channel[i] - uint8_t, non-zero if i-th channel needs to be muted/unmuted
+ * Number of channels passed is equal to XENSND_OP_OPEN request pcm_channels
+ * field
+ */
+
+struct xensnd_mute_req {
+};
+
+struct xensnd_unmute_req {
+};
+
+/*
+ * All response packets have the same length (64 bytes)
+ *
+ * Response for all requests:
+ * 0 1 2 3 octet
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | id | operation | stream_idx |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | padding |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | status | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ * +-----------------+-----------------+-----------------+-----------------+
+ * | reserved |
+ * +-----------------+-----------------+-----------------+-----------------+
+ *
+ * id - uint16_t, copied from the request
+ * stream_idx - uint8_t, copied from request
+ * operation - uint8_t, XENSND_OP_XXX - copied from request
+ * status - int8_t, response status (XENSND_RSP_???)
+ */
+
+struct xensnd_request {
+ uint8_t raw[64];
+};
+
+struct xensnd_response {
+ uint8_t raw[64];
+};
+
+union xensnd_req {
+ struct xensnd_request raw;
+ struct {
+ uint16_t id;
+ uint8_t operation;
+ uint8_t stream_idx;
+ uint32_t padding;
+ union {
+ struct xensnd_open_req open;
+ struct xensnd_close_req close;
+ struct xensnd_write_req write;
+ struct xensnd_read_req read;
+ struct xensnd_get_vol_req get_vol;
+ struct xensnd_set_vol_req set_vol;
+ struct xensnd_mute_req mute;
+ struct xensnd_unmute_req unmute;
+ } op;
+ } data;
+};
+
+union xensnd_resp {
+ struct xensnd_response raw;
+ struct {
+ uint16_t id;
+ uint8_t operation;
+ uint8_t stream_idx;
+ int8_t status;
+ } data;
+};
+
+DEFINE_RING_TYPES(xen_sndif, struct xensnd_req, struct xensnd_resp);
+
+#endif /* __XEN_PUBLIC_IO_XENSND_H__ */