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[Xen-devel] [PATCH v7] sndif: add ABI for Para-virtual sound



This is ABI for the two halves of a Para-virtual
sound driver to communicate with each to other.

Signed-off-by: Oleksandr Dmytryshyn <oleksandr.dmytryshyn@xxxxxxxxxxxxxxx>
Signed-off-by: Iurii Konovalenko <iurii.konovalenko@xxxxxxxxxxxxxxx>
---
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

 xen/include/public/io/sndif.h | 429 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 429 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 0000000..0118cab
--- /dev/null
+++ b/xen/include/public/io/sndif.h
@@ -0,0 +1,429 @@
+/******************************************************************************
+ * 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.
+ */
+
+#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
+ *****************************************************************************
+ *
+ *------------------------- Backend Device parameters -------------------------
+ *
+ * devid
+ *      Values:         <uint32_t>
+ *
+ *      Index of the soundcard which will be created in the frontend. This
+ *      index is zero based.
+ *
+ * devcnt
+ *      Values:         <uint32_t>
+ *
+ *      PCM instances count that are created by the soundcard in the frontend.
+ *
+ *----------------------------- Streams settings ------------------------------
+ *
+ * Every virtualized device has own set of the sound streams. Each stream
+ * parameter is with index "%u" and defined as 'stream%u_???'. Stream index is
+ * zero based and should be continuous in range from 0 to 'streams_cnt' - 1.
+ *
+ * stream%u_channels
+ *      Values:         <uint32_t>
+ *
+ *      The maximum amount of channels that can be supported by this stream.
+ *      Should be from 1 to XENSND_MAX_CHANNELS_PER_STREAM.
+ *
+ * stream%u_type
+ *      Values:         "p", "c", "b"
+ *
+ *      Stream type: "p" - playback stream, "c" - capture stream,
+ *      "b" - both playback and capture stream.
+ *
+ * stream%u_bedev_p
+ *      Values:         string
+ *
+ *      Name of the playback sound device which is mapped to this stream
+ *      by the backend. Present if stream%u_type is "p" or "b"
+ *
+ * stream%u_bedev_c
+ *      Values:         string
+ *
+ *      Name of the cappture sound device which is mapped to this stream
+ *      by the backend. Present if stream%u_type is "c" or "b"
+ *
+ * stream%u_devid
+ *      Values:         <uint32_t>
+ *
+ *      Index of the PCM instance which is created by the soundcard
+ *      in the frontend.
+ *
+ *****************************************************************************
+ *                            Frontend XenBus Nodes
+ *****************************************************************************
+ *
+ *----------------------- 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
+ *      the sole page in a single page sized ring buffer.
+ */
+
+/*
+ * STATE DIAGRAMS
+ *
+ *****************************************************************************
+ *                                   Startup                                 *
+ *****************************************************************************
+ *
+ * Tool stack creates front and back nodes with state XenbusStateInitialising.
+ *
+ * Front                                Back
+ * =================================    =====================================
+ * XenbusStateInitialising              XenbusStateInitialising
+ *  o Query virtual device               o Query backend device identification
+ *    properties.                          data.
+ *  o Setup OS device instance.          o Open and validate backend device.
+ *                                       o Publish backend features and
+ *                                         transport parameters.
+ *                                                      |
+ *                                                      |
+ *                                                      V
+ *                                      XenbusStateInitWait
+ *
+ * o Query backend features and
+ *   transport parameters.
+ * o Allocate and initialize the
+ *   request ring.
+ * o Publish transport parameters
+ *   that will be in effect during
+ *   this connection.
+ *              |
+ *              |
+ *              V
+ * XenbusStateInitialised
+ *
+ *                                       o Query frontend transport parameters.
+ *                                       o Connect to the request ring and
+ *                                         event channel.
+ *                                       o Publish backend device properties.
+ *                                                      |
+ *                                                      |
+ *                                                      V
+ *                                      XenbusStateConnected
+ *
+ *  o Query backend device properties.
+ *  o Finalize OS virtual device
+ *    instance.
+ *              |
+ *              |
+ *              V
+ * XenbusStateConnected
+ *
+ * Note: Drivers that do not support any optional features, or the negotiation
+ *       of transport parameters, can skip certain states in the state machine:
+ *
+ *       o A frontend may transition to XenbusStateInitialised without
+ *         waiting for the backend to enter XenbusStateInitWait.  In this
+ *         case, default transport parameters are in effect and any
+ *         transport parameters published by the frontend must contain
+ *         their default values.
+ *
+ *       o A backend may transition to XenbusStateInitialised, bypassing
+ *         XenbusStateInitWait, without waiting for the frontend to first
+ *         enter the XenbusStateInitialised state.  In this case, default
+ *         transport parameters are in effect and any transport parameters
+ *         published by the backend must contain their default values.
+ *
+ *       Drivers that support optional features and/or transport parameter
+ *       negotiation must tolerate these additional state transition paths.
+ *       In general this means performing the work of any skipped state
+ *       transition, if it has not already been performed, in addition to the
+ *       work associated with entry into the current state.
+ */
+
+/*
+ * 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
+#define XENSND_PCM_FORMAT_SPECIAL       31 /* Any other unspecified format */
+
+/*
+ * 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
+
+/*
+ * The maximum amount of shared pages which can be used in any request
+ * from the frontend driver to the backend driver
+ */
+#define XENSND_MAX_PAGES_PER_REQUEST    10
+
+/* The maximum amount of channels per virtualized stream */
+#define XENSND_MAX_CHANNELS_PER_STREAM  128
+
+/*
+ * 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 to other using an shared page and event channel.
+ * Shared page contains a ring with request/response packets.
+ * All fields within the packet are always in little-endian byte order.
+ * Almost all fields within the packet are unsigned except
+ * the field 'status' in the responses packets which is signed.
+ *
+ *
+ * All request packets have the same length (64 bytes)
+ *
+ * Request open - open an pcm stream for playback or capture:
+ *     0    1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |                      id                       |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       operation       |      stream_idx       |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |      pcm_format       |      pcm_channels     |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       pcm_rate        |       reserved        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       reserved        |       reserved        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/+
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       reserved        |       reserved        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ * id - private guest value, echoed in resp
+ * operation - XENSND_OP_OPEN
+ * stream_idx - index of the stream (from 0 to 'streams_cnt' - 1.
+ *   'streams_cnt' is read from the XenStore)
+ * pcm_format - XENSND_PCM_FORMAT_???
+ * pcm_channels - channels count in stream
+ * pcm_rate - stream data rate
+ *
+ *
+ * Request close - close an opened pcm stream:
+ *     0    1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |                      id                       |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       operation       |       stream_idx      |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       reserved        |       reserved        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/+
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       reserved        |       reserved        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ * id - private guest value, echoed in resp
+ * operation - XENSND_OP_CLOSE
+ * stream_idx - index of the stream (from 0 to 'streams_cnt' - 1.
+ *   'streams_cnt' is read from the XenStore)
+ *
+ *
+ * Request read/write - used for read (for capture) or write (for playback):
+ *     0    1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |                      id                       |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       operation       |       stream_idx      |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |         length        |         gref0         |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |         gref1         |         gref2         |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/+
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |          gref9        |       reserved        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ * id - private guest value, echoed in resp
+ * operation - XENSND_OP_READ or XENSND_OP_WRITE
+ * stream_idx - index of the stream (from 0 to 'streams_cnt' - 1.
+ *   'streams_cnt' is read from the XenStore)
+ * length - read or write data length
+ * gref0 - gref9 - references to a grant entries for used pages in read/write
+ * request.
+ *
+ *
+ * Request set volume - set/get channels volume in stream:
+ *     0    1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |                      id                       |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       operation       |       stream_idx      |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |         gref          |       reserved        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       reserved        |       reserved        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/+
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       reserved        |       reserved        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ * id - private guest value, echoed in resp
+ * operation - XENSND_OP_SET_VOLUME or XENSND_OP_GET_VOLUME
+ * stream_idx - index of the stream (from 0 to 'streams_cnt' - 1.
+ *   'streams_cnt' is read from the XenStore)
+ * gref - references to a grant entry for page with the volume values
+ *
+ *
+ * Shared page for set/get volume:
+ *
+ *     0    1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |        vol_ch0        |        vol_ch1        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |        vol_ch2        |        vol_ch3        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/+
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       vol_ch126       |       vol_ch127       |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ * vol_ch0 - vol_ch127 - volume for the channel from 0 to
+ *   XENSND_MAX_CHANNELS_PER_STREAM
+ * Please, note that only first 'stream%u_channels' are used in this command,
+ *   where 'stream%u_channels' is read from the XenStore (channels count for
+ *   stream with index '%u' which equals to 'stream_idx')
+ *
+ *
+ * All response packets have the same length (64 bytes)
+ *
+ * Response for all requests:
+ *     0    1     2     3     4     5     6     7  octet
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |                      id                       |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       operation       |         status        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       stream_idx      |       reserved        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       reserved        |       reserved        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * +/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/+
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ * |       reserved        |       reserved        |
+ * +-----+-----+-----+-----+-----+-----+-----+-----+
+ *
+ * id - copied from request
+ * stream_idx - copied from request
+ * operation - XENSND_OP_??? - copied from request
+ * status - XENSND_RSP_???
+ */
+
+struct xensnd_request {
+    uint8_t raw[64];
+};
+
+struct xensnd_response {
+    uint8_t raw[64];
+};
+
+DEFINE_RING_TYPES(xensnd, struct xensnd_request, struct xensnd_response);
+
+#endif /* __XEN_PUBLIC_IO_XENSND_H__ */
-- 
1.9.1


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