    /******************************************************************************
     * displif.h
     *
     * Unified display 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) 2016-2017 EPAM Systems Inc.
     *
     * Authors: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
     *          Oleksandr Grytsov <oleksandr_grytsov@epam.com>
     */

    #ifndef __XEN_PUBLIC_IO_DISPLIF_H__
    #define __XEN_PUBLIC_IO_DISPLIF_H__

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

    /*
     ******************************************************************************
     *                           Protocol version
     ******************************************************************************
     */
    #define XENDISPL_PROTOCOL_VERSION     "1"

    /*
     ******************************************************************************
     *                  Main features provided by the protocol
     ******************************************************************************
     * This protocol aims to provide a unified protocol which fits more
     * sophisticated use-cases than a framebuffer device can handle. At the
     * moment basic functionality is supported with the intention to be extended:
     *  o multiple dynamically allocated/destroyed framebuffers
     *  o buffers of arbitrary sizes
     *  o buffer allocation at either back or front end
     *  o better configuration options including multiple display support
     *
     * Note: existing fbif can be used together with displif running at the
     * same time, e.g. on Linux one provides framebuffer and another DRM/KMS
     *
     * Note: display resolution (XenStore's "resolution" property) defines
     * visible area of the virtual display. At the same time resolution of
     * the display and frame buffers may differ: buffers can be smaller, equal
     * or bigger than the visible area. This is to enable use-cases, where backend
     * may do some post-processing of the display and frame buffers supplied,
     * e.g. those buffers can be just a part of the final composition.
     *
     ******************************************************************************
     *                        Direction of improvements
     ******************************************************************************
     * Future extensions to the existing protocol may include:
     *  o display/connector cloning
     *  o allocation of objects other than display buffers
     *  o plane/overlay support
     *  o scaling support
     *  o rotation support
     *
     ******************************************************************************
     *                  Feature and Parameter Negotiation
     ******************************************************************************
     *
     * Front->back notifications: when enqueuing a new request, sending a
     * notification can be made conditional on xendispl_req (i.e., the generic
     * hold-off mechanism provided by the ring macros). Backends must set
     * xendispl_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 xendispl_resp (i.e., the generic
     * hold-off mechanism provided by the ring macros). Frontends must set
     * xendispl_resp appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
     *
     * The two halves of a para-virtual display 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 display connectors
     * than the underlying HW physically has by employing SW graphics compositors
     *
     * This is an example of backend and frontend configuration:
     *
     *--------------------------------- Backend -----------------------------------
     *
     * /local/domain/0/backend/vdispl/1/0/frontend-id = "1"
     * /local/domain/0/backend/vdispl/1/0/frontend = "/local/domain/1/device/vdispl/0"
     * /local/domain/0/backend/vdispl/1/0/state = "4"
     * /local/domain/0/backend/vdispl/1/0/versions = "1,2"
     *
     *--------------------------------- Frontend ----------------------------------
     *
     * /local/domain/1/device/vdispl/0/backend-id = "0"
     * /local/domain/1/device/vdispl/0/backend = "/local/domain/0/backend/vdispl/1/0"
     * /local/domain/1/device/vdispl/0/state = "4"
     * /local/domain/1/device/vdispl/0/version = "1"
     * /local/domain/1/device/vdispl/0/be-alloc = "1"
     *
     *-------------------------- Connector 0 configuration ------------------------
     *
     * /local/domain/1/device/vdispl/0/0/resolution = "1920x1080"
     * /local/domain/1/device/vdispl/0/0/req-ring-ref = "2832"
     * /local/domain/1/device/vdispl/0/0/req-event-channel = "15"
     * /local/domain/1/device/vdispl/0/0/evt-ring-ref = "387"
     * /local/domain/1/device/vdispl/0/0/evt-event-channel = "16"
     *
     *-------------------------- Connector 1 configuration ------------------------
     *
     * /local/domain/1/device/vdispl/0/1/resolution = "800x600"
     * /local/domain/1/device/vdispl/0/1/req-ring-ref = "2833"
     * /local/domain/1/device/vdispl/0/1/req-event-channel = "17"
     * /local/domain/1/device/vdispl/0/1/evt-ring-ref = "388"
     * /local/domain/1/device/vdispl/0/1/evt-event-channel = "18"
     *
     ******************************************************************************
     *                            Backend XenBus Nodes
     ******************************************************************************
     *
     *----------------------------- Protocol version ------------------------------
     *
     * versions
     *      Values:         <string>
     *
     *      List of XENDISPL_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.
     *
     * conn-idx
     *      Values:         <uint8_t>
     *
     *      Zero based contigous index of the connector.
     *      /local/domain/<dom-id>/device/vdispl/<dev-id>/<conn-idx>/...
     *
     *----------------------------- Protocol version ------------------------------
     *
     * version
     *      Values:         <string>
     *
     *      Protocol version, chosen among the ones supported by the backend.
     *
     *------------------------- Backend buffer allocation -------------------------
     *
     * be-alloc
     *      Values:         "0", "1"
     *
     *      If value is set to "1", then backend can be a buffer provider/allocator
     *      for this domain during XENDISPL_OP_DBUF_CREATE operation (see below
     *      for negotiation).
     *      If value is not "1" or omitted frontend must allocate buffers itself.
     *
     *----------------------------- Connector settings ----------------------------
     *
     * resolution
     *      Values:         <width, uint32_t>x<height, uint32_t>
     *
     *      Width and height of the connector in pixels separated by
     *      XENDISPL_RESOLUTION_SEPARATOR. This defines visible area of the
     *      display.
     *
     *------------------ Connector Request Transport Parameters -------------------
     *
     * This communication path is used to deliver requests from frontend to backend
     * and get the corresponding responses from backend to frontend,
     * set up per connector.
     *
     * req-event-channel
     *      Values:         <uint32_t>
     *
     *      The identifier of the Xen connector's control event channel
     *      used to signal activity in the ring buffer.
     *
     * req-ring-ref
     *      Values:         <uint32_t>
     *
     *      The Xen grant reference granting permission for the backend to map
     *      a sole page of connector's control ring buffer.
     *
     *------------------- Connector Event Transport Parameters --------------------
     *
     * This communication path is used to deliver asynchronous events from backend
     * to frontend, set up per connector.
     *
     * evt-event-channel
     *      Values:         <uint32_t>
     *
     *      The identifier of the Xen connector's event channel
     *      used to signal activity in the ring buffer.
     *
     * evt-ring-ref
     *      Values:         <uint32_t>
     *
     *      The Xen grant reference granting permission for the backend to map
     *      a sole page of connector's event ring buffer.
     */

    /*
     ******************************************************************************
     *                               STATE DIAGRAMS
     ******************************************************************************
     *
     * Tool stack creates front and back state nodes with initial state
     * XenbusStateInitialising.
     * Tool stack creates and sets up frontend display configuration
     * nodes per domain.
     *
     *-------------------------------- Normal flow --------------------------------
     *
     * 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
     *   connector.
     * 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 display connectors
     *    as per configuration.
     *              |
     *              |
     *              V
     * XenbusStateConnected
     *
     *                                      XenbusStateUnknown
     *                                      XenbusStateClosed
     *                                      XenbusStateClosing
     * o Remove virtual display 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 is 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.
     * 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.
     *
     ******************************************************************************
     *                             REQUEST CODES
     ******************************************************************************
     * Request codes [0; 15] are reserved and must not be used
     */

    #define XENDISPL_OP_DBUF_CREATE       0x10
    #define XENDISPL_OP_DBUF_DESTROY      0x11
    #define XENDISPL_OP_FB_ATTACH         0x12
    #define XENDISPL_OP_FB_DETACH         0x13
    #define XENDISPL_OP_SET_CONFIG        0x14
    #define XENDISPL_OP_PG_FLIP           0x15

    /*
     ******************************************************************************
     *                                 EVENT CODES
     ******************************************************************************
     */
    #define XENDISPL_EVT_PG_FLIP          0x00

    /*
     ******************************************************************************
     *               XENSTORE FIELD AND PATH NAME STRINGS, HELPERS
     ******************************************************************************
     */
    #define XENDISPL_DRIVER_NAME          "vdispl"

    #define XENDISPL_LIST_SEPARATOR       ","
    #define XENDISPL_RESOLUTION_SEPARATOR "x"

    #define XENDISPL_FIELD_BE_VERSIONS    "versions"
    #define XENDISPL_FIELD_FE_VERSION     "version"
    #define XENDISPL_FIELD_REQ_RING_REF   "req-ring-ref"
    #define XENDISPL_FIELD_REQ_CHANNEL    "req-event-channel"
    #define XENDISPL_FIELD_EVT_RING_REF   "evt-ring-ref"
    #define XENDISPL_FIELD_EVT_CHANNEL    "evt-event-channel"
    #define XENDISPL_FIELD_RESOLUTION     "resolution"
    #define XENDISPL_FIELD_BE_ALLOC       "be-alloc"

    /*
     ******************************************************************************
     *                          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 display driver communicate with
     * each other using shared pages and event channels.
     * Shared page contains a ring with request/response packets.
     *
     * All reserved fields in the structures below must be 0.
     * Display buffers's cookie of value 0 is treated as invalid.
     * Framebuffer's cookie of value 0 is treated as invalid.
     *
     * For all request/response/event packets that use cookies:
     *   dbuf_cookie - uint64_t, unique to guest domain value used by the backend
     *     to map remote display buffer to its local one
     *   fb_cookie - uint64_t, unique to guest domain value used by the backend
     *     to map remote framebuffer to its local one
     *
     *---------------------------------- Requests ---------------------------------
     *
     * All requests/responses, which are not connector specific, must be sent over
     * control ring of the connector which has the index value of 0:
     *   /local/domain/<dom-id>/device/vdispl/<dev-id>/0/req-ring-ref
     *
     * All request packets have the same length (64 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, XENDISPL_OP_???
     *
     * Request dbuf creation - request creation of a display buffer.
     *         0                1                 2               3        octet
     * +----------------+----------------+----------------+----------------+
     * |               id                |_OP_DBUF_CREATE |   reserved     | 4
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 8
     * +----------------+----------------+----------------+----------------+
     * |                       dbuf_cookie low 32-bit                      | 12
     * +----------------+----------------+----------------+----------------+
     * |                       dbuf_cookie high 32-bit                     | 16
     * +----------------+----------------+----------------+----------------+
     * |                               width                               | 20
     * +----------------+----------------+----------------+----------------+
     * |                               height                              | 24
     * +----------------+----------------+----------------+----------------+
     * |                                bpp                                | 28
     * +----------------+----------------+----------------+----------------+
     * |                             buffer_sz                             | 32
     * +----------------+----------------+----------------+----------------+
     * |                               flags                               | 36
     * +----------------+----------------+----------------+----------------+
     * |                           gref_directory                          | 40
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 44
     * +----------------+----------------+----------------+----------------+
     * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 64
     * +----------------+----------------+----------------+----------------+
     *
     * Must be sent over control ring of the connector which has the index
     * value of 0:
     *   /local/domain/<dom-id>/device/vdispl/<dev-id>/0/req-ring-ref
     * All unused bits in flags field must be set to 0.
     *
     * An attempt to create multiple display buffers with the same dbuf_cookie is
     * an error. dbuf_cookie can be re-used after destroying the corresponding
     * display buffer.
     *
     * Width and height of the display buffers can be smaller, equal or bigger
     * than the connector's resolution. Depth/pixel format of the individual
     * buffers can differ as well.
     *
     * width - uint32_t, width in pixels
     * height - uint32_t, height in pixels
     * bpp - uint32_t, bits per pixel
     * buffer_sz - uint32_t, buffer size to be allocated, octets
     * flags - uint32_t, flags of the operation
     *   o XENDISPL_DBUF_FLG_REQ_ALLOC - if set, then backend is requested
     *     to allocate the buffer with the parameters provided in this request.
     *     Page directory is handled as follows:
     *       Frontend on request:
     *         o allocates pages for the directory (gref_directory,
     *           gref_dir_next_page(s)
     *         o grants permissions for the pages of the directory to the backend
     *         o sets gref_dir_next_page fields
     *       Backend on response:
     *         o grants permissions for the pages of the buffer allocated to
     *           the frontend
     *         o fills in page directory with grant references
     *           (gref[] in struct xendispl_page_directory)
     * 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)
     */

    #define XENDISPL_DBUF_FLG_REQ_ALLOC       (1 << 0)

    struct xendispl_dbuf_create_req {
        uint64_t dbuf_cookie;
        uint32_t width;
        uint32_t height;
        uint32_t bpp;
        uint32_t buffer_sz;
        uint32_t flags;
        grant_ref_t gref_directory;
    };

    /*
     * Shared page for XENDISPL_OP_DBUF_CREATE 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 XENDISPL_OP_DBUF_CREATE
     *
     * Number of grant_ref_t entries in the whole page directory is not
     * passed, but instead can be calculated as:
     *   num_grefs_total = (XENDISPL_OP_DBUF_CREATE.buffer_sz + XEN_PAGE_SIZE - 1) /
     *       XEN_PAGE_SIZE
     */

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

    /*
     * Request dbuf destruction - destroy a previously allocated display buffer:
     *         0                1                 2               3        octet
     * +----------------+----------------+----------------+----------------+
     * |               id                |_OP_DBUF_DESTROY|   reserved     | 4
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 8
     * +----------------+----------------+----------------+----------------+
     * |                       dbuf_cookie low 32-bit                      | 12
     * +----------------+----------------+----------------+----------------+
     * |                       dbuf_cookie high 32-bit                     | 16
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 20
     * +----------------+----------------+----------------+----------------+
     * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 64
     * +----------------+----------------+----------------+----------------+
     *
     * Must be sent over control ring of the connector which has the index
     * value of 0:
     *   /local/domain/<dom-id>/device/vdispl/<dev-id>/0/req-ring-ref
     */

    struct xendispl_dbuf_destroy_req {
        uint64_t dbuf_cookie;
    };

    /*
     * Request framebuffer attachment - request attachment of a framebuffer to
     * previously created display buffer.
     *         0                1                 2               3        octet
     * +----------------+----------------+----------------+----------------+
     * |               id                | _OP_FB_ATTACH  |   reserved     | 4
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 8
     * +----------------+----------------+----------------+----------------+
     * |                       dbuf_cookie low 32-bit                      | 12
     * +----------------+----------------+----------------+----------------+
     * |                       dbuf_cookie high 32-bit                     | 16
     * +----------------+----------------+----------------+----------------+
     * |                        fb_cookie low 32-bit                       | 20
     * +----------------+----------------+----------------+----------------+
     * |                        fb_cookie high 32-bit                      | 24
     * +----------------+----------------+----------------+----------------+
     * |                               width                               | 28
     * +----------------+----------------+----------------+----------------+
     * |                               height                              | 32
     * +----------------+----------------+----------------+----------------+
     * |                            pixel_format                           | 36
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 40
     * +----------------+----------------+----------------+----------------+
     * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 64
     * +----------------+----------------+----------------+----------------+
     *
     * Must be sent over control ring of the connector which has the index
     * value of 0:
     *   /local/domain/<dom-id>/device/vdispl/<dev-id>/0/req-ring-ref
     * Width and height can be smaller, equal or bigger than the connector's
     * resolution.
     *
     * An attempt to create multiple frame buffers with the same fb_cookie is
     * an error. fb_cookie can be re-used after destroying the corresponding
     * frame buffer.
     *
     * width - uint32_t, width in pixels
     * height - uint32_t, height in pixels
     * pixel_format - uint32_t, pixel format of the framebuffer, FOURCC code
     */

    struct xendispl_fb_attach_req {
        uint64_t dbuf_cookie;
        uint64_t fb_cookie;
        uint32_t width;
        uint32_t height;
        uint32_t pixel_format;
    };

    /*
     * Request framebuffer detach - detach a previously
     * attached framebuffer from the display buffer in request:
     *         0                1                 2               3        octet
     * +----------------+----------------+----------------+----------------+
     * |               id                |  _OP_FB_DETACH |   reserved     | 4
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 8
     * +----------------+----------------+----------------+----------------+
     * |                        fb_cookie low 32-bit                       | 12
     * +----------------+----------------+----------------+----------------+
     * |                        fb_cookie high 32-bit                      | 16
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 20
     * +----------------+----------------+----------------+----------------+
     * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 64
     * +----------------+----------------+----------------+----------------+
     *
     * Must be sent over control ring of the connector which has the index
     * value of 0:
     *   /local/domain/<dom-id>/device/vdispl/<dev-id>/0/req-ring-ref
     */

    struct xendispl_fb_detach_req {
        uint64_t fb_cookie;
    };

    /*
     * Request configuration set/reset - request to set or reset
     * the configuration/mode of the display:
     *         0                1                 2               3        octet
     * +----------------+----------------+----------------+----------------+
     * |               id                | _OP_SET_CONFIG |   reserved     | 4
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 8
     * +----------------+----------------+----------------+----------------+
     * |                        fb_cookie low 32-bit                       | 12
     * +----------------+----------------+----------------+----------------+
     * |                        fb_cookie high 32-bit                      | 16
     * +----------------+----------------+----------------+----------------+
     * |                                 x                                 | 20
     * +----------------+----------------+----------------+----------------+
     * |                                 y                                 | 24
     * +----------------+----------------+----------------+----------------+
     * |                               width                               | 28
     * +----------------+----------------+----------------+----------------+
     * |                               height                              | 32
     * +----------------+----------------+----------------+----------------+
     * |                                bpp                                | 40
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 44
     * +----------------+----------------+----------------+----------------+
     * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 64
     * +----------------+----------------+----------------+----------------+
     *
     * Pass all zeros to reset, otherwise command is treated as
     * configuration set.
     * Framebuffer's cookie defines which framebuffer/dbuf must be
     * displayed while enabling display (applying configuration).
     * x, y, width and height are bound by the connector's resolution and must not
     * exceed it.
     *
     * x - uint32_t, starting position in pixels by X axis
     * y - uint32_t, starting position in pixels by Y axis
     * width - uint32_t, width in pixels
     * height - uint32_t, height in pixels
     * bpp - uint32_t, bits per pixel
     */

    struct xendispl_set_config_req {
        uint64_t fb_cookie;
        uint32_t x;
        uint32_t y;
        uint32_t width;
        uint32_t height;
        uint32_t bpp;
    };

    /*
     * Request page flip - request to flip a page identified by the framebuffer
     * cookie:
     *         0                1                 2               3        octet
     * +----------------+----------------+----------------+----------------+
     * |               id                | _OP_PG_FLIP    |   reserved     | 4
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 8
     * +----------------+----------------+----------------+----------------+
     * |                        fb_cookie low 32-bit                       | 12
     * +----------------+----------------+----------------+----------------+
     * |                        fb_cookie high 32-bit                      | 16
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 20
     * +----------------+----------------+----------------+----------------+
     * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 64
     * +----------------+----------------+----------------+----------------+
     */

    struct xendispl_page_flip_req {
        uint64_t fb_cookie;
    };

    /*
     *---------------------------------- Responses --------------------------------
     *
     * All response packets have the same length (64 octets)
     *
     * All response packets have common header:
     *         0                1                 2               3        octet
     * +----------------+----------------+----------------+----------------+
     * |               id                |            reserved             | 4
     * +----------------+----------------+----------------+----------------+
     * |                              status                               | 8
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 12
     * +----------------+----------------+----------------+----------------+
     * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 64
     * +----------------+----------------+----------------+----------------+
     *
     * id - uint16_t, private guest value, echoed from request
     * status - int32_t, response status, zero on success and -XEN_EXX on failure
     *
     *----------------------------------- Events ----------------------------------
     *
     * Events are sent via a shared page allocated by the front and propagated by
     *   evt-event-channel/evt-ring-ref XenStore entries
     * All event packets have the same length (64 octets)
     * All event packets have common header:
     *         0                1                 2               3        octet
     * +----------------+----------------+----------------+----------------+
     * |               id                |      type      |   reserved     | 4
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 8
     * +----------------+----------------+----------------+----------------+
     *
     * id - uint16_t, event id, may be used by front
     * type - uint8_t, type of the event
     *
     *
     * Page flip complete event - event from back to front on page flip completed:
     *         0                1                 2               3        octet
     * +----------------+----------------+----------------+----------------+
     * |               id                |   _EVT_PG_FLIP |   reserved     | 4
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 8
     * +----------------+----------------+----------------+----------------+
     * |                        fb_cookie low 32-bit                       | 12
     * +----------------+----------------+----------------+----------------+
     * |                        fb_cookie high 32-bit                      | 16
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 20
     * +----------------+----------------+----------------+----------------+
     * |/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
     * +----------------+----------------+----------------+----------------+
     * |                             reserved                              | 64
     * +----------------+----------------+----------------+----------------+
     */

    struct xendispl_pg_flip_evt {
        uint64_t fb_cookie;
    };

    struct xendispl_req {
        uint16_t id;
        uint8_t operation;
        uint8_t reserved[5];
        union {
            struct xendispl_dbuf_create_req dbuf_create;
            struct xendispl_dbuf_destroy_req dbuf_destroy;
            struct xendispl_fb_attach_req fb_attach;
            struct xendispl_fb_detach_req fb_detach;
            struct xendispl_set_config_req set_config;
            struct xendispl_page_flip_req pg_flip;
            uint8_t reserved[56];
        } op;
    };

    struct xendispl_resp {
        uint16_t id;
        uint8_t operation;
        uint8_t reserved;
        int32_t status;
        uint8_t reserved1[56];
    };

    struct xendispl_evt {
        uint16_t id;
        uint8_t type;
        uint8_t reserved[5];
        union {
            struct xendispl_pg_flip_evt pg_flip;
            uint8_t reserved[56];
        } op;
    };

    DEFINE_RING_TYPES(xen_displif, struct xendispl_req, struct xendispl_resp);

    /*
     ******************************************************************************
     *                        Back to front events delivery
     ******************************************************************************
     * In order to deliver asynchronous events from back to front a shared page is
     * allocated by front and its granted reference propagated to back via
     * XenStore entries (evt-ring-ref/evt-event-channel).
     * This page has a common header used by both front and back to synchronize
     * access and control event's ring buffer, while back being a producer of the
     * events and front being a consumer. The rest of the page after the header
     * is used for event packets.
     *
     * Upon reception of an event(s) front may confirm its reception
     * for either each event, group of events or none.
     */

    struct xendispl_event_page {
        uint32_t in_cons;
        uint32_t in_prod;
        uint8_t reserved[56];
    };

    #define XENDISPL_EVENT_PAGE_SIZE 4096
    #define XENDISPL_IN_RING_OFFS (sizeof(struct xendispl_event_page))
    #define XENDISPL_IN_RING_SIZE (XENDISPL_EVENT_PAGE_SIZE - XENDISPL_IN_RING_OFFS)
    #define XENDISPL_IN_RING_LEN (XENDISPL_IN_RING_SIZE / sizeof(struct xendispl_evt))
    #define XENDISPL_IN_RING(page) \
    	((struct xendispl_evt *)((char *)(page) + XENDISPL_IN_RING_OFFS))
    #define XENDISPL_IN_RING_REF(page, idx) \
    	(XENDISPL_IN_RING((page))[(idx) % XENDISPL_IN_RING_LEN])

    #endif /* __XEN_PUBLIC_IO_DISPLIF_H__ */

    /*
     * Local variables:
     * mode: C
     * c-file-style: "BSD"
     * c-basic-offset: 4
     * tab-width: 4
     * indent-tabs-mode: nil
     * End:
     */