Re: [PATCH v18] xen/sndif: Add sound-device ABI

[Oleksandr Andrushchenko <andr2000@gmail.com>]

ping


On 03/20/2017 09:03 AM, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
>
> Add ABI for the two halves of a para-virtualized
> sound driver to communicate with each other.
>
> The ABI allows implementing audio playback and capture as
> well as volume control and possibility to mute/unmute
> audio sources.
>
> 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. Thus, allowing fine tunned configurations per
> frontend.
>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> Signed-off-by: Oleksandr Grytsov <oleksandr_grytsov@epam.com>
> Signed-off-by: Oleksandr Dmytryshyn <oleksandr.dmytryshyn@globallogic.com>
> Signed-off-by: Iurii Konovalenko <iurii.konovalenko@globallogic.com>
>
> ---
> Changes since v1:
>   * removed __attribute__((__packed__)) from all structures definitions
>
> Changes since v2:
>   * removed all C structures
>   * added protocol description between frontend and backend drivers
>
> Changes since v3:
>   * fixed some typos
>   * renamed XENSND_PCM_FORMAT_FLOAT_** to XENSND_PCM_FORMAT_F32_**
>   * renamed XENSND_PCM_FORMAT_FLOAT64_** to XENSND_PCM_FORMAT_F64_**
>   * added 'id' field to the request and response packets
>   * renamed 'stream_id' to 'stream' in the packets description
>   * renamed 'pcm_data_rate' to 'pcm_rate' in the packets description
>   * renamed 'pcm_stream_type' to 'pcm_type' in the packets description
>   * removed 'stream_id' field from the response packets
>
> Changes since v4:
>   * renamed 'stream_id' back to the to 'stream' in the packets description
>   * moved 'id' field to the upper position in the response packets
>
> Changes since v5:
>   * Slightly reworked request/response packets
>   * Size of the request/response packet is changed to the 64 bytes
>   * Now parameters for the XENSND_OP_SET_VOLUME/XENSND_OP_GET_VOLUME are
>     passed via shared page
>   * Added parameters for the XenBus nodes (now each stream can be mapped
>     to the defined sound device in the backend using those parameters)
>   * Added XenBus state diagrams description
>
> Changes since v6:
>   * Reworked streams description  in the Backend XenBus Nodes
>
> Changes since v7:
>   * re-worked backend device parameters to be more generic and flexible
>   * extended frontend device parameters
>   * slightly updated state machine description added mute/unmute commands
>   * added constants for XenStore configuration strings
>     (fields, PCM formats etc.)
>   * changed request/response structure size from 64 octets to 16
>   * introduced dynamic buffer allocation instead of
>     static XENSND_MAX_PAGES_PER_REQUEST
>   * re-worked open request to allow dynamic buffer allocation
>   * re-worked read/write/volume requests, so they don't pass grefs:
>     buffer from the open request is used for these operations to pass data
>   * specified type of the volume value to be a signed value in steps
>     of 0.001 dBm, while 0 being 0dBm.
>   * added Linux include file with structure definitions
>
> Changes since v8:
>   * changed frontend-id to frontend_id
>   * single sound card support, configured with bunch of
>     devices/streams
>   * clarifucation made on sample rates and formats expressed as
>     decimals w/o any particular ordering
>   * put description of migration/disconnection state
>   * replaced __attribute__((packed)) to __packed
>   * changed padding of ring structures to 64 to fit cache line
>   * removeed #ifdef __KERNEL
>   * explicitly stated which indices in XenStore configuration
>     are contiguous
>   * added description to what frontend's defaults are
>   * made names of virtual card/devices optional
>   * removed PCM_FORMAT_SPECIAL
>   * changed volume units from dBm to dB
>
> Changes since v9:
>   * removed sndif_linux.h
>   * moved all structures from sndif_linux.h to sndif.h
>   * structures padded where needed
>   * fixed Hz comment
>
> Changes since v10:
>   * fixed tabs to 4 spaces to comply with Xen coding style
>   * added placeholders to empty structures (C89 concern)
>   * added missing header includes
>
> Changes since v11:
>   * added XENSND_RSP_NOTSUPP error code
>   * changed gref[0] to gref[1] with comment
>   * modified comments on empty structures
>   * removed "__" from member names
>   * fixed indentation
>   * added padding in union xensnd_resp
>   * changed __XEN_PUBLIC_IO_XENSND_H__ to __XEN_PUBLIC_IO_SNDIF_H__
>
> Changes since v12:
>   * changed indentation for defines
>   * missed ";" after gref[1]
>   * documentation changes
>   * changed req/resp structures
>   * changed xensnd_page_directory structure
>   * pass buffer size in open request
>
> Changes since v13:
>   * note on usage of grant ref 0
>   * all page sizes are XEN_PAGE_SIZE
>   * padding/reserved cleanup/fixes
>   * removed empty structures
>
> Changes since v14:
>   * turn padding into reserved
>
> Changes since v15:
>   * protocol description reworked
>   * added offset to block notations
>   * used -XEN_EXX for status reporting
>   * added protocol versioning
>   * removed stream_idx from the packet structure
>   * changed xenstore paths
>
> Changes since v16:
>   * updated XenStore path pattern
>   * removed unused XenStore helper string constants
>   * renamed gref_directory_start to gref_directory
>   * added offset/length to volume, mute, unmute
>   * added note on async use-cases
>   * struct xensnd_rw_req is now used for read/write,
>     volume set/get, mute, unmute
>
> Changes since v17:
>   * add recovery flow into state diagrams section
>   * re-position struct xensnd_rw_req in the document
>   * make a note on common use of xensnd_rw_req for
>     read/write, volume get/set, mute/unmute
>   * add missing string constants for XenStore "versions"
>     and "version" fields
>   * add editor's block
> ---
>
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> ---
>   xen/include/public/io/sndif.h | 803 ++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 803 insertions(+)
>   create mode 100644 xen/include/public/io/sndif.h
>
> diff --git a/xen/include/public/io/sndif.h b/xen/include/public/io/sndif.h
> new file mode 100644
> index 000000000000..c5c1978406b3
> --- /dev/null
> +++ b/xen/include/public/io/sndif.h
> @@ -0,0 +1,803 @@
> +/******************************************************************************
> + * 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__ */
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * tab-width: 4
> + * indent-tabs-mode: nil
> + * End:
> + */


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