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Re: [Xen-devel] [PATCH v3 1/1] cameraif: add ABI for para-virtual camera
- To: Hans Verkuil <hverkuil@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, konrad.wilk@xxxxxxxxxx, jgross@xxxxxxxx, boris.ostrovsky@xxxxxxxxxx, mchehab@xxxxxxxxxx, linux-media@xxxxxxxxxxxxxxx, sakari.ailus@xxxxxxxxxxxxxxx, koji.matsuoka.xm@xxxxxxxxxxx
- From: Oleksandr Andrushchenko <andr2000@xxxxxxxxx>
- Date: Mon, 14 Jan 2019 11:23:41 +0200
- Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
- Delivery-date: Mon, 14 Jan 2019 09:23:55 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Hello, Hans!
Could you please take a look at my answers below and kindly let me know
if we are ready for (final?) v4 from your point of view.
Konrad, Xen-devel - do you have any objections/comments on this?
Thank you,
Oleksandr
On 12/17/18 9:37 AM, Oleksandr Andrushchenko wrote:
Hello, Hans!
Thank you for reviewing, please find my answers inline
On 12/14/18 2:14 PM, Hans Verkuil wrote:
Hi Oleksandr,
This is looking a lot better than v2. I do have a few remaining
comments about
some things that are a bit unclear to me.
On 12/12/18 10:49 AM, Oleksandr Andrushchenko wrote:
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
This is the ABI for the two halves of a para-virtualized
camera driver which extends Xen's reach multimedia capabilities even
farther enabling it for video conferencing, In-Vehicle Infotainment,
high definition maps etc.
The initial goal is to support most needed functionality with the
final idea to make it possible to extend the protocol if need be:
1. Provide means for base virtual device configuration:
- pixel formats
- resolutions
- frame rates
2. Support basic camera controls:
- contrast
- brightness
- hue
- saturation
3. Support streaming control
Signed-off-by: Oleksandr Andrushchenko
<oleksandr_andrushchenko@xxxxxxxx>
---
xen/include/public/io/cameraif.h | 1374
++++++++++++++++++++++++++++++
1 file changed, 1374 insertions(+)
create mode 100644 xen/include/public/io/cameraif.h
diff --git a/xen/include/public/io/cameraif.h
b/xen/include/public/io/cameraif.h
new file mode 100644
index 000000000000..9aae0f47743b
--- /dev/null
+++ b/xen/include/public/io/cameraif.h
@@ -0,0 +1,1374 @@
+/******************************************************************************
+ * cameraif.h
+ *
+ * Unified camera 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) 2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
+ */
+
+#ifndef __XEN_PUBLIC_IO_CAMERAIF_H__
+#define __XEN_PUBLIC_IO_CAMERAIF_H__
+
+#include "ring.h"
+#include "../grant_table.h"
+
+/*
+
******************************************************************************
+ * Protocol version
+
******************************************************************************
+ */
+#define XENCAMERA_PROTOCOL_VERSION "1"
+
+/*
+
******************************************************************************
+ * Feature and Parameter Negotiation
+
******************************************************************************
+ *
+ * Front->back notifications: when enqueuing a new request, sending a
+ * notification can be made conditional on xencamera_req (i.e., the
generic
+ * hold-off mechanism provided by the ring macros). Backends must set
+ * xencamera_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 xencamera_resp (i.e.,
the generic
+ * hold-off mechanism provided by the ring macros). Frontends must set
+ * xencamera_resp appropriately (e.g., using
RING_FINAL_CHECK_FOR_RESPONSES()).
+ *
+ * The two halves of a para-virtual camera 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 formatted node string, without loss of information.
+ *
+
******************************************************************************
+ * Example configuration
+
******************************************************************************
+ *
+ * This is an example of backend and frontend configuration:
+ *
+ *--------------------------------- Backend
-----------------------------------
+ *
+ * /local/domain/0/backend/vcamera/1/0/frontend-id = "1"
+ * /local/domain/0/backend/vcamera/1/0/frontend =
"/local/domain/1/device/vcamera/0"
+ * /local/domain/0/backend/vcamera/1/0/state = "4"
+ * /local/domain/0/backend/vcamera/1/0/versions = "1,2"
+ *
+ *--------------------------------- Frontend
----------------------------------
+ *
+ * /local/domain/1/device/vcamera/0/backend-id = "0"
+ * /local/domain/1/device/vcamera/0/backend =
"/local/domain/0/backend/vcamera/1"
+ * /local/domain/1/device/vcamera/0/state = "4"
+ * /local/domain/1/device/vcamera/0/version = "1"
+ * /local/domain/1/device/vcamera/0/be-alloc = "1"
+ *
+ *---------------------------- Device 0 configuration
-------------------------
+ *
+ * /local/domain/1/device/vcamera/0/max-buffers = "3"
+ * /local/domain/1/device/vcamera/0/controls = "contrast,hue"
+ *
/local/domain/1/device/vcamera/0/formats/YUYV/640x480/frame-rates =
"30/1,15/1"
+ *
/local/domain/1/device/vcamera/0/formats/YUYV/1920x1080/frame-rates
= "15/2"
+ *
/local/domain/1/device/vcamera/0/formats/BGRA/640x480/frame-rates =
"15/1,15/2"
+ *
/local/domain/1/device/vcamera/0/formats/BGRA/1200x720/frame-rates =
"15/2"
+ * /local/domain/1/device/vcamera/0/unique-id = "0"
+ * /local/domain/1/device/vcamera/0/req-ring-ref = "2832"
+ * /local/domain/1/device/vcamera/0/req-event-channel = "15"
+ * /local/domain/1/device/vcamera/0/evt-ring-ref = "387"
+ * /local/domain/1/device/vcamera/0/evt-event-channel = "16"
+ *
+ *---------------------------- Device 1 configuration
-------------------------
+ *
+ * /local/domain/1/device/vcamera/1/max-buffers = "8"
+ * /local/domain/1/device/vcamera/1/controls =
"brightness,saturation,hue"
+ *
/local/domain/1/device/vcamera/1/formats/YUYV/640x480/frame-rates =
"30/1,15/2"
+ *
/local/domain/1/device/vcamera/1/formats/YUYV/1920x1080/frame-rates
= "15/2"
+ * /local/domain/1/device/vcamera/1/unique-id = "1"
+ * /local/domain/1/device/vcamera/1/req-ring-ref = "2833"
+ * /local/domain/1/device/vcamera/1/req-event-channel = "17"
+ * /local/domain/1/device/vcamera/1/evt-ring-ref = "388"
+ * /local/domain/1/device/vcamera/1/evt-event-channel = "18"
+ *
+
******************************************************************************
+ * Backend XenBus Nodes
+
******************************************************************************
+ *
+ *----------------------------- Protocol version
------------------------------
+ *
+ * versions
+ * Values: <string>
+ * | index | reserved | 12
+ *
+ * List of XENCAMERA_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.
+ *
+ * /local/domain/<dom-id>/device/vcamera/<dev-id>/...
+ *
+ *----------------------------- 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 will be the buffer
+ * provider/allocator for this domain during
XENCAMERA_OP_BUF_CREATE
+ * operation.
+ * If value is not "1" or omitted frontend must allocate
buffers itself.
+ *
+ *------------------------------- Camera settings
-----------------------------
+ *
+ * unique-id
+ * Values: <string>
+ *
+ * After device instance initialization each camera is assigned a
+ * unique ID, so it can be identified by the backend by this ID.
+ * This can be UUID or such.
+ *
+ * max-buffers
+ * Values: <uint8_t>
+ *
+ * Maximum number of camera buffers this frontend may use.
Who determines this value? The backend?
This is determined by the system integrator while configuring
the system, e.g. depending on use-cases every domain will have
its own requirements on number of buffers needed. Knowing that
one can optimize memory usage and allow some of the domains more
buffers and have some of those limited.
So how does this relate to num_bufs when requesting buffers? Will
num_bufs
be clamped to max-buffers?
The number of buffers here is up to the SW running in a guest domain,
for example, if we allow the guest to use up to max-buffers it is
still up to guest's software to request max-buffers or less.
I don't really understand the use-case of this setting and the
description
is very short and vague.
The backend needs to know how many buffers will be used as
the worst case, so while requesting buffers from host driver
it can allocate the maximum from the start. This allows solving
the use-case when first guest requests less buffers than others and
requests streaming (so at this moment backend needs to allocate the
buffers
and also start streaming) and then a new guest with bigger number of
buffers
comes. So, to make the implementation simpler we configure the backend
to allocate max(guest[i].max_buffers) buffers on start.
+ *
+ * controls
+ * Values: <list of string>
+ *
+ * List of supported camera controls separated by
XENCAMERA_LIST_SEPARATOR.
+ * Camera controls are expressed as a list of string values
w/o any
+ * ordering requirement.
+ *
+ * formats
+ * Values: <format, char[7]>
+ *
+ * Formats are organized as a set of directories one per each
+ * supported pixel format. The name of the directory is the
+ * corresponding FOURCC string label. The next level of
+ * the directory under <formats> represents supported
resolutions.
+ * If the format represents a big-endian variant of a little
+ * endian format, then the "-BE" suffix must be added. E.g.
'AR15' vs
+ * 'AR15-BE'.
+ * If FOURCC string label has spaces then those are only
allowed to
+ * be at the end of the label and must be trimmed.
It might be useful to give examples for this: 'Y16' and 'Y16-BE' should
clarify how the trimming of spaces work.
Ok, will add
+ *
+ * resolution
+ * Values: <width, uint32_t>x<height, uint32_t>
+ *
+ * Resolutions are organized as a set of directories one per each
+ * supported resolution under corresponding <formats> directory.
+ * The name of the directory is the supported width and height
+ * of the camera resolution in pixels.
+ *
+ * frame-rates
+ * Values: <numerator, uint32_t>/<denominator, uint32_t>
+ *
+ * List of XENCAMERA_FRAME_RATE_SEPARATOR separated supported
frame rates
+ * of the camera expressed as numerator and denominator of the
+ * corresponding frame rate.
+ *
+ *------------------- Camera 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 virtual camera device.
+ *
+ * req-event-channel
+ * Values: <uint32_t>
+ *
+ * The identifier of the Xen camera'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 camera's control ring buffer.
+ *
+ *-------------------- Camera Event Transport Parameters
----------------------
+ *
+ * This communication path is used to deliver asynchronous events
from backend
+ * to frontend, set up per virtual camera device.
+ *
+ * evt-event-channel
+ * Values: <uint32_t>
+ *
+ * The identifier of the Xen camera'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 camera'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 camera 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
+ * camera.
+ * 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 camera as per
+ * configuration.
+ * |
+ * |
+ * V
+ * XenbusStateConnected
+ *
+ * XenbusStateUnknown
+ * XenbusStateClosed
+ * XenbusStateClosing
+ * o Remove virtual camera 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
+
******************************************************************************
+ */
+#define XENCAMERA_OP_CONFIG_SET 0x00
+#define XENCAMERA_OP_CONFIG_GET 0x01
+#define XENCAMERA_OP_CONFIG_VALIDATE 0x02
+#define XENCAMERA_OP_FRAME_RATE_SET 0x03
+#define XENCAMERA_OP_BUF_GET_LAYOUT 0x04
+#define XENCAMERA_OP_BUF_REQUEST 0x05
+#define XENCAMERA_OP_BUF_CREATE 0x06
+#define XENCAMERA_OP_BUF_DESTROY 0x07
+#define XENCAMERA_OP_BUF_QUEUE 0x08
+#define XENCAMERA_OP_BUF_DEQUEUE 0x09
+#define XENCAMERA_OP_CTRL_ENUM 0x0a
+#define XENCAMERA_OP_CTRL_SET 0x0b
+#define XENCAMERA_OP_CTRL_GET 0x0c
+#define XENCAMERA_OP_STREAM_START 0x0d
+#define XENCAMERA_OP_STREAM_STOP 0x0e
+
+#define XENCAMERA_CTRL_BRIGHTNESS 0
+#define XENCAMERA_CTRL_CONTRAST 1
+#define XENCAMERA_CTRL_SATURATION 2
+#define XENCAMERA_CTRL_HUE 3
+
+/* Number of supported controls. */
+#define XENCAMERA_MAX_CTRL 4
+
+/* Control is read-only. */
+#define XENCAMERA_CTRL_FLG_RO (1 << 0)
+/* Control is write-only. */
+#define XENCAMERA_CTRL_FLG_WO (1 << 1)
+/* Control's value is volatile. */
+#define XENCAMERA_CTRL_FLG_VOLATILE (1 << 2)
+
+/* Supported color spaces. */
+#define XENCAMERA_COLORSPACE_DEFAULT 0
+#define XENCAMERA_COLORSPACE_SMPTE170M 1
+#define XENCAMERA_COLORSPACE_REC709 2
+#define XENCAMERA_COLORSPACE_SRGB 3
+#define XENCAMERA_COLORSPACE_OPRGB 4
+#define XENCAMERA_COLORSPACE_BT2020 5
+#define XENCAMERA_COLORSPACE_DCI_P3 6
+
+/* Color space transfer function. */
+#define XENCAMERA_XFER_FUNC_DEFAULT 0
+#define XENCAMERA_XFER_FUNC_709 1
+#define XENCAMERA_XFER_FUNC_SRGB 2
+#define XENCAMERA_XFER_FUNC_OPRGB 3
+#define XENCAMERA_XFER_FUNC_NONE 4
+#define XENCAMERA_XFER_FUNC_DCI_P3 5
+#define XENCAMERA_XFER_FUNC_SMPTE2084 6
+
+/* Color space Y’CbCr encoding. */
+#define XENCAMERA_YCBCR_ENC_IGNORE 0
+#define XENCAMERA_YCBCR_ENC_601 1
+#define XENCAMERA_YCBCR_ENC_709 2
+#define XENCAMERA_YCBCR_ENC_XV601 3
+#define XENCAMERA_YCBCR_ENC_XV709 4
+#define XENCAMERA_YCBCR_ENC_BT2020 5
+#define XENCAMERA_YCBCR_ENC_BT2020_CONST_LUM 6
+
+/* Quantization range. */
+#define XENCAMERA_QUANTIZATION_DEFAULT 0
+#define XENCAMERA_QUANTIZATION_FULL_RANGE 1
+#define XENCAMERA_QUANTIZATION_LIM_RANGE 2
+
+/*
+
******************************************************************************
+ * EVENT CODES
+
******************************************************************************
+ */
+#define XENCAMERA_EVT_FRAME_AVAIL 0x00
+#define XENCAMERA_EVT_CTRL_CHANGE 0x01
+
+/* Resolution has changed. */
+#define XENCAMERA_EVT_CFG_FLG_RESOL (1 << 0)
+
+/*
+
******************************************************************************
+ * XENSTORE FIELD AND PATH NAME STRINGS, HELPERS
+
******************************************************************************
+ */
+#define XENCAMERA_DRIVER_NAME "vcamera"
+
+#define XENCAMERA_LIST_SEPARATOR ","
+#define XENCAMERA_RESOLUTION_SEPARATOR "x"
+#define XENCAMERA_FRACTION_SEPARATOR "/"
+
+#define XENCAMERA_FIELD_BE_VERSIONS "versions"
+#define XENCAMERA_FIELD_FE_VERSION "version"
+#define XENCAMERA_FIELD_REQ_RING_REF "req-ring-ref"
+#define XENCAMERA_FIELD_REQ_CHANNEL "req-event-channel"
+#define XENCAMERA_FIELD_EVT_RING_REF "evt-ring-ref"
+#define XENCAMERA_FIELD_EVT_CHANNEL "evt-event-channel"
+#define XENCAMERA_FIELD_MAX_BUFFERS "max-buffers"
+#define XENCAMERA_FIELD_CONTROLS "controls"
+#define XENCAMERA_FIELD_FORMATS "formats"
+#define XENCAMERA_FIELD_FRAME_RATES "frame-rates"
+#define XENCAMERA_FIELD_BE_ALLOC "be-alloc"
+#define XENCAMERA_FIELD_UNIQUE_ID "unique-id"
+
+#define XENCAMERA_CTRL_BRIGHTNESS_STR "brightness"
+#define XENCAMERA_CTRL_CONTRAST_STR "contrast"
+#define XENCAMERA_CTRL_SATURATION_STR "saturation"
+#define XENCAMERA_CTRL_HUE_STR "hue"
+
+#define XENCAMERA_FOURCC_BIGENDIAN_STR "-BE"
+
+/* Maximum number of buffer planes supported. */
+#define XENCAMERA_MAX_PLANE 4
+
+/*
+
******************************************************************************
+ * STATUS RETURN CODES
+
******************************************************************************
+ *
+ * Status return code is zero on success and -XEN_EXX on failure.
+ *
+
******************************************************************************
+ * Assumptions
+
******************************************************************************
+ *
+ * - 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.
+ * - all references in this document to page sizes must be treated
+ * as pages of size XEN_PAGE_SIZE unless otherwise noted.
+ * - all FOURCC mappings used for configuration and messaging are
+ * Linux V4L2 ones:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/videodev2.h
+ * with the following exceptions:
+ * - characters are allowed in [0x20; 0x7f] range
+ * - when used for XenStore configuration entries the following
+ * are not allowed:
+ * - '/', '\', ' ' (space), '<', '>', ':', '"', '|', '?', '*'
+ * - if trailing spaces are part of the FOURCC code then
those must be
+ * trimmed
+ *
+ *
+
******************************************************************************
+ * Description of the protocol between frontend and backend
driver
+
******************************************************************************
+ *
+ * The two halves of a Para-virtual camera 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.
+ *
+ * For all request/response/event packets:
+ * - frame rate parameter is represented as a pair of 4 octet long
+ * numerator and denominator:
+ * - frame_rate_numer - uint32_t, numerator of the frame rate
+ * - frame_rate_denom - uint32_t, denominator of the frame rate
+ * The corresponding frame rate (Hz) is calculated as:
+ * frame_rate = frame_rate_numer / frame_rate_denom
+ * - buffer index is a zero based index of the buffer. Must be
less than
+ * the value of XENCAMERA_OP_CONFIG_SET.num_bufs response:
+ * - index - uint8_t, index of the buffer.
+ *
+ *
+ *---------------------------------- Requests
---------------------------------
+ *
+ * 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, XENCAMERA_OP_XXX.
+ *
+ *
+ * Request to set/validate the configuration - request to set the
+ * configuration/mode of the camera (XENCAMERA_OP_CONFIG_SET) or to
+ * check if the configuration is valid and can be used
+ * (XENCAMERA_OP_CONFIG_VALIDATE):
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _OP_CONFIG_XXX |
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | pixel
format | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | width | 16
+ *
+----------------+----------------+----------------+----------------+
+ * | height | 20
+ *
+----------------+----------------+----------------+----------------+
+ * | colorspace | 24
+ *
+----------------+----------------+----------------+----------------+
+ * | xfer_func | 28
+ *
+----------------+----------------+----------------+----------------+
+ * | ycbcr_enc | 32
+ *
+----------------+----------------+----------------+----------------+
+ * | quantization | 36
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 40
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * pixel_format - uint32_t, pixel format to be used, FOURCC code.
+ * width - uint32_t, width in pixels.
+ * height - uint32_t, height in pixels.
+ * colorspace - uint32_t, this supplements pixel_format parameter,
+ * one of the XENCAMERA_COLORSPACE_XXX.
+ * xfer_func - uint32_t, this supplements colorspace parameter,
+ * one of the XENCAMERA_XFER_FUNC_XXX.
+ * ycbcr_enc - uint32_t, this supplements colorspace parameter,
+ * one of the XENCAMERA_YCBCR_ENC_XXX. Please note, that
ycbcr_enc is only
+ * valid for YCbCr pixelformats and should be ignored otherwise.
+ * quantization - uint32_t, this supplements colorspace parameter,
+ * one of the XENCAMERA_QUANTIZATION_XXX.
Should you really include colorspace, xfer_func, ycbcr_enc and
quantization
here? They should be in the response, but for now at least all video
capture
drivers just set these fields. I.e., you cannot request a specific
e.g. colorspace.
It might become possible in the future, but I think it is
out-of-scope for
the purpose of this Xen project.
Yes, after implementing the front driver I was not really convinced
we need these, but decided to keep. But, yes, I'll remove these from
the request and have them in the response as you suggest.
+ *
+ * See response format for this request.
+ *
+ * Notes:
+ * - the only difference between XENCAMERA_OP_CONFIG_VALIDATE and
+ * XENCAMERA_OP_CONFIG_SET is that the former doesn't actually
change
+ * camera configuration, but queries if the configuration is valid.
+ * This can be used while stream is active and/or buffers
allocated.
+ * - frontend must check the corresponding response in order to see
+ * if the values reported back by the backend do match the
desired ones
+ * and can be accepted.
+ * - frontend may send multiple XENCAMERA_OP_CONFIG_SET requests
before
+ * sending XENCAMERA_OP_STREAM_START request to update or tune the
+ * final stream configuration.
+ * - configuration cannot be changed during active streaming, e.g.
+ * after XENCAMERA_OP_STREAM_START and before
XENCAMERA_OP_STREAM_STOP
+ * requests.
+ */
+struct xencamera_config_req {
+ uint32_t pixel_format;
+ uint32_t width;
+ uint32_t height;
+ uint32_t colorspace;
+ uint32_t xfer_func;
+ uint32_t ycbcr_enc;
+ uint32_t quantization;
+};
+
+/*
+ * Request current configuration of the camera:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _OP_CONFIG_GET |
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * See response format for this request.
+ *
+ *
+ * Request to set the frame rate of the stream:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _FRAME_RATE_SET|
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | frame_rate_numer | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | frame_rate_denom | 16
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 20
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * frame_rate_numer - uint32_t, numerator of the frame rate.
+ * frame_rate_denom - uint32_t, denominator of the frame rate.
+ *
+ * Notes:
+ * - to query the current (actual) frame rate use
XENCAMERA_OP_CONFIG_GET
+ * request.
+ * - this request can be used with camera buffers allocated, but
stream
+ * stopped, e.g. frontend is allowed to stop the stream with
+ * XENCAMERA_OP_STREAM_STOP, hold the buffers allocated (e.g.
keep the
+ * configuration set with XENCAMERA_OP_CONFIG_SET), change the
+ * frame rate of the stream and (re)start the stream again with
+ * XENCAMERA_OP_STREAM_START.
+ * - frame rate cannot be changed during active streaming, e.g.
+ * after XENCAMERA_OP_STREAM_START and before
XENCAMERA_OP_STREAM_STOP
+ * commands.
+ */
+struct xencamera_frame_rate_req {
+ uint32_t frame_rate_numer;
+ uint32_t frame_rate_denom;
+};
+
+/*
+ * Request camera buffer's layout:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _BUF_GET_LAYOUT|
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * See response format for this request.
+ *
+ *
+ * Request number of buffers to be used:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _OP_BUF_REQUEST|
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | num_bufs | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 16
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * num_bufs - uint8_t, desired number of buffers to be used.
If num_bufs is limited to max-buffers, then that should be mentioned
here.
Good point, will add a note
Also, this op requests the buffers from the backend, right? I don't
think that is explicitly stated.
Yes, it requests from the backend. And I am not sure we need
to put any clarification here as all the requests come from
front to back, so it is "by design"
+ *
+ * See response format for this request.
+ *
+ * Notes:
+ * - frontend must check the corresponding response in order to see
+ * if the values reported back by the backend do match the
desired ones
+ * and can be accepted.
+ * - frontend may send multiple XENCAMERA_OP_BUF_REQUEST requests
before
+ * sending XENCAMERA_OP_STREAM_START request to update or tune the
+ * configuration.
Perhaps mention that every time you call it any existing buffers are
destroyed
and an attempt is made to allocate new buffers, as per the request.
So calling this op again will *not* allocate additional buffers.
Well, this is somewhat different from V4L2: this operation doesn't
necessarily allocate buffers (but, in V4L2 based backed it does ;)
The real buffer allocation (according to this protocol) happens when
frontend calls XENCAMERA_OP_BUF_CREATE operation. So, despite the fact
that V4L2 based front/back do what you describe - others may not follow
this convention: this operation just declares that this number of buffer
is desired
+ * - after this request camera configuration cannot be changed,
unless
+ * streaming is stopped and buffers destroyed
+ * - passing zero num_bufs in this request (after streaming has
stopped
+ * and all buffers destroyed) unblocks camera configuration
changes.
I think this last note should not be a note at all but part of the
num_bufs
description. It reads like an afterthought right now when in fact it is
rather important.
Agree, will put it together with num_bufs description
+ */
+struct xencamera_buf_request {
+ uint8_t num_bufs;
+};
+
+/*
+ * Request camera buffer creation:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _OP_BUF_CREATE |
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | index | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | plane_offset[0] | 16
+ *
+----------------+----------------+----------------+----------------+
+ * | plane_offset[1] | 20
+ *
+----------------+----------------+----------------+----------------+
+ * | plane_offset[2] | 24
+ *
+----------------+----------------+----------------+----------------+
+ * | plane_offset[3] | 28
+ *
+----------------+----------------+----------------+----------------+
+ * | gref_directory | 32
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 36
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
And this op deals with frontend buffers, right?
Yes, as I explained before all requests always come from front
to back, so this is the frontend requesting the backend to use
these offsets
+ *
+ * An attempt to create multiple buffers with the same index is an
error.
+ * index can be re-used after destroying the corresponding camera
buffer.
+ *
+ * index - uint8_t, index of the buffer to be created.
How does this index relate to num_bufs in the previous op and with the
max-buffers setting? I expect that the index is in the range
[0...num_bufs-1].
Yes, you are right. I'll put explicit index range here, so
it is clear.
+ * plane_offset - array of uint32_t, offset of the corresponding plane
+ * in octets from the buffer start. Number of offsets returned is
+ * equal to the value returned in
XENCAMERA_OP_BUF_GET_LAYOUT.num_planes.
+ * gref_directory - grant_ref_t, a reference to the first shared page
+ * describing shared buffer references. The size of the buffer is
equal to
+ * XENCAMERA_OP_BUF_GET_LAYOUT.size response. At least one page
exists. If
+ * shared buffer size exceeds what can be addressed by this
single page,
+ * then reference to the next shared page must be supplied (see
+ * gref_dir_next_page below).
+ *
+ * If XENCAMERA_FIELD_BE_ALLOC configuration entry is set, then
backend will
+ * allocate the buffer with the parameters provided in this request
and page
+ * directory is handled as follows:
+ * Frontend on request:
+ * - allocates pages for the directory (gref_directory,
+ * gref_dir_next_page(s)
+ * - grants permissions for the pages of the directory to the
backend
+ * - sets gref_dir_next_page fields
+ * Backend on response:
+ * - grants permissions for the pages of the buffer allocated to
+ * the frontend
+ * - fills in page directory with grant references
+ * (gref[] in struct xencamera_page_directory)
+ */
+struct xencamera_buf_create_req {
+ uint8_t index;
+ uint8_t reserved[3];
+ uint32_t plane_offset[XENCAMERA_MAX_PLANE];
+ grant_ref_t gref_directory;
+};
+
+/*
+ * Shared page for XENCAMERA_OP_BUF_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 XENCAMERA_OP_BUF_CREATE.
+ *
+ * Number of grant_ref_t entries in the whole page directory is not
+ * passed, but instead can be calculated as:
+ * num_grefs_total = (XENCAMERA_OP_BUF_REQUEST.size +
XEN_PAGE_SIZE - 1) /
+ * XEN_PAGE_SIZE
+ */
+struct xencamera_page_directory {
+ grant_ref_t gref_dir_next_page;
+ grant_ref_t gref[1]; /* Variable length */
+};
+
+/*
+ * Request buffer destruction - destroy a previously allocated
camera buffer:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _OP_BUF_DESTROY|
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | index | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 16
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * index - uint8_t, index of the buffer to be destroyed.
+ *
+ *
+ * Request queueing of the buffer for backend use:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _OP_BUF_QUEUE |
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | index | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 16
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * Notes:
+ * - frontends must not access the buffer content after this
request until
+ * response to XENCAMERA_OP_BUF_DEQUEUE has been received.
+ * - buffers must be queued to the backend before destroying them
with
+ * XENCAMERA_OP_BUF_DESTROY.
+ *
+ * index - uint8_t, index of the buffer to be queued.
+ *
+ *
+ * Request dequeueing of the buffer for frontend use:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id |_OP_BUF_DEQUEUE |
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | index | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 16
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * Notes:
+ * - frontend is allowed to access the buffer content after the
corresponding
+ * response to this request.
+ *
+ * index - uint8_t, index of the buffer to be queued.
+ *
+ *
+ * Request camera control details:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _OP_CTRL_ENUM |
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | index | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 16
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * See response format for this request.
+ *
+ * index - uint8_t, index of the control to be queried.
+ */
+struct xencamera_index {
+ uint8_t index;
+};
+
+/*
+ * Request camera control change:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _OP_SET_CTRL |
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | type | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 16
+ *
+----------------+----------------+----------------+----------------+
+ * | value low
32-bit | 20
+ *
+----------------+----------------+----------------+----------------+
+ * | value high
32-bit | 24
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 28
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * type - uint8_t, type of the control, one of the XENCAMERA_CTRL_XXX.
+ * value - int64_t, new value of the control.
+ */
+struct xencamera_ctrl_value {
+ uint8_t type;
+ uint8_t reserved[7];
+ int64_t value;
+};
+
+/*
+ * Request camera control state:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _OP_GET_CTRL |
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | type | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * See response format for this request.
+ *
+ * type - uint8_t, type of the control, one of the XENCAMERA_CTRL_XXX.
+ */
+struct xencamera_get_ctrl_req {
+ uint8_t type;
+};
+
+/*
+ * Request camera capture stream start:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id |_OP_STREAM_START|
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ *
+ * Request camera capture stream stop:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id |_OP_STREAM_STOP |
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ *
+ *---------------------------------- Responses
--------------------------------
+ *
+ * All response packets have the same length (64 octets).
+ *
+ * All response packets have common header:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | operation | reserved
| 4
+ *
+----------------+----------------+----------------+----------------+
+ * | status | 8
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * id - uint16_t, copied from the request.
+ * operation - uint8_t, XENCAMERA_OP_* - copied from request.
+ * status - int32_t, response status, zero on success and -XEN_EXX
on failure.
+ *
+ *
+ * Configuration response - response for XENCAMERA_OP_CONFIG_SET,
+ * XENCAMERA_OP_CONFIG_GET and XENCAMERA_OP_CONFIG_VALIDATE requests:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _OP_CONFIG_XXX | reserved
| 4
+ *
+----------------+----------------+----------------+----------------+
+ * | status | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | pixel
format | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | width | 16
+ *
+----------------+----------------+----------------+----------------+
+ * | height | 20
+ *
+----------------+----------------+----------------+----------------+
+ * | colorspace | 24
+ *
+----------------+----------------+----------------+----------------+
+ * | xfer_func | 28
+ *
+----------------+----------------+----------------+----------------+
+ * | ycbcr_enc | 32
+ *
+----------------+----------------+----------------+----------------+
+ * | quantization | 36
+ *
+----------------+----------------+----------------+----------------+
+ * | displ_asp_ratio_numer | 40
+ *
+----------------+----------------+----------------+----------------+
+ * | displ_asp_ratio_denom | 44
+ *
+----------------+----------------+----------------+----------------+
+ * | frame_rate_numer | 48
+ *
+----------------+----------------+----------------+----------------+
+ * | frame_rate_denom | 52
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 56
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * Meaning of the corresponding values in this response is the same
as for
+ * XENCAMERA_OP_CONFIG_SET and XENCAMERA_OP_FRAME_RATE_SET requests.
+ *
+ * displ_asp_ratio_numer - uint32_t, numerator of the display
aspect ratio.
+ * displ_asp_ratio_denom - uint32_t, denominator of the display
aspect ratio.
+ */
+struct xencamera_config_resp {
+ uint32_t pixel_format;
+ uint32_t width;
+ uint32_t height;
+ uint32_t colorspace;
+ uint32_t xfer_func;
+ uint32_t ycbcr_enc;
+ uint32_t quantization;
+ uint32_t displ_asp_ratio_numer;
+ uint32_t displ_asp_ratio_denom;
+ uint32_t frame_rate_numer;
+ uint32_t frame_rate_denom;
+};
+
+/*
+ * Request buffer response - response for XENCAMERA_OP_BUF_GET_LAYOUT
+ * request:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id |_BUF_GET_LAYOUT | reserved
| 4
+ *
+----------------+----------------+----------------+----------------+
+ * | status | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | num_planes | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | size | 16
+ *
+----------------+----------------+----------------+----------------+
+ * | plane_size[0] | 20
+ *
+----------------+----------------+----------------+----------------+
+ * | plane_size[1] | 24
+ *
+----------------+----------------+----------------+----------------+
+ * | plane_size[2] | 28
+ *
+----------------+----------------+----------------+----------------+
+ * | plane_size[3] | 32
+ *
+----------------+----------------+----------------+----------------+
+ * | plane_stride[0] | 36
+ *
+----------------+----------------+----------------+----------------+
+ * | plane_stride[1] | 40
+ *
+----------------+----------------+----------------+----------------+
+ * | plane_stride[2] | 44
+ *
+----------------+----------------+----------------+----------------+
+ * | plane_stride[3] | 48
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * num_planes - uint8_t, number of planes of the buffer.
+ * size - uint32_t, overall size of the buffer including sizes of the
+ * individual planes and padding if applicable.
+ * plane_size - array of uint32_t, size in octets of the
corresponding plane
+ * including padding.
+ * plane_stride - array of uint32_t, size in octets occupied by the
+ * corresponding single image line including padding if applicable.
+ *
+ * Note! The sizes and strides in this response apply to all
buffers created
+ * with XENCAMERA_OP_BUF_CREATE command, but individual buffers may
have
+ * different plane offsets, see XENCAMERA_OP_BUF_REQUEST.plane_offset.
+ */
+struct xencamera_buf_get_layout_resp {
+ uint8_t num_planes;
+ uint8_t reserved[3];
+ uint32_t size;
+ uint32_t plane_size[XENCAMERA_MAX_PLANE];
+ uint32_t plane_stride[XENCAMERA_MAX_PLANE];
+};
+
+/*
+ * Request buffer response - response for XENCAMERA_OP_BUF_REQUEST
+ * request:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id |_OP_BUF_REQUEST | reserved
| 4
+ *
+----------------+----------------+----------------+----------------+
+ * | status | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | num_buffers | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 16
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * num_buffers - uint8_t, number of buffers to be used.
+ *
+ *
+ * Control enumerate response - response for XENCAMERA_OP_CTRL_ENUM:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _OP_CTRL_ENUM | reserved
| 4
+ *
+----------------+----------------+----------------+----------------+
+ * | status | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | index | type | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | flags | 16
+ *
+----------------+----------------+----------------+----------------+
+ * | min low
32-bits | 20
+ *
+----------------+----------------+----------------+----------------+
+ * | min high
32-bits | 24
+ *
+----------------+----------------+----------------+----------------+
+ * | max low
32-bits | 28
+ *
+----------------+----------------+----------------+----------------+
+ * | max high
32-bits | 32
+ *
+----------------+----------------+----------------+----------------+
+ * | step low
32-bits | 36
+ *
+----------------+----------------+----------------+----------------+
+ * | step high
32-bits | 40
+ *
+----------------+----------------+----------------+----------------+
+ * | def_val low
32-bits | 44
+ *
+----------------+----------------+----------------+----------------+
+ * | def_val high
32-bits | 48
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 52
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * index - uint8_t, index of the camera control in response.
+ * type - uint8_t, type of the control, one of the XENCAMERA_CTRL_XXX.
+ * flags - uint32_t, flags of the control, one of the
XENCAMERA_CTRL_FLG_XXX.
+ * min - int64_t, minimum value of the control.
+ * max - int64_t, maximum value of the control.
+ * step - int64_t, minimum size in which control value can be changed.
+ * def_val - int64_t, default value of the control.
+ */
+struct xencamera_ctrl_enum_resp {
+ uint8_t index;
+ uint8_t type;
+ uint8_t reserved[2];
+ uint32_t flags;
+ int64_t min;
+ int64_t max;
+ int64_t step;
+ int64_t def_val;
+};
+
+/*
+ * Get control response - response for XENCAMERA_OP_CTRL_GET:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id | _OP_CTRL_GET | reserved
| 4
+ *
+----------------+----------------+----------------+----------------+
+ * | status | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | type | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 16
+ *
+----------------+----------------+----------------+----------------+
+ * | value low
32-bit | 20
+ *
+----------------+----------------+----------------+----------------+
+ * | value high
32-bit | 24
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 28
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * type - uint8_t, type of the control, one of the XENCAMERA_CTRL_XXX.
+ * value - int64_t, new value of the control.
+ */
+
+/*
+ *----------------------------------- 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.
+ *
+ *
+ * Frame captured event - event from back to front when a new captured
+ * frame is available:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id |_EVT_FRAME_AVAIL|
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | index | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | used_sz | 16
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 20
+ *
+----------------+----------------+----------------+----------------+
+ * | seq_num low
32-bits | 24
+ *
+----------------+----------------+----------------+----------------+
+ * | seq_num high
32-bits | 28
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 20
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * index - uint8_t, index of the buffer that contains new captured
frame.
+ * used_sz - uint32_t, number of octets this frame has. This can be
less
+ * than the XENCAMERA_OP_BUF_REQUEST.size (response) for compressed
formats.
+ * seq_num - uint64_t, sequential number of the frame. Must be
+ * monotonically increasing. If skips are detected in seq_num
then that
+ * means that the frames in-between were dropped.
Hmm, add this line:
Note however that not all video capture hardware is capable of
detecting dropped frames.
In that case there will be no skips in the sequence counter.
ok, will add
+ */
+struct xencamera_frame_avail_evt {
+ uint8_t index;
+ uint8_t reserved0[3];
+ uint32_t used_sz;
+ uint8_t reserved1[4];
+ uint64_t seq_num;
Why use a uint64_t? The sequence number is a u32.
Ah, this is for V4L2 ;) But, ok, 64-bit is overkill here, will trim to
32.
+};
+
+/*
+ * Control change event- event from back to front when camera control
+ * has changed:
+ * 0 1 2 3 octet
+ *
+----------------+----------------+----------------+----------------+
+ * | id |_EVT_CTRL_CHANGE|
reserved | 4
+ *
+----------------+----------------+----------------+----------------+
+ * | type | reserved | 8
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 12
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 16
+ *
+----------------+----------------+----------------+----------------+
+ * | value low
32-bit | 20
+ *
+----------------+----------------+----------------+----------------+
+ * | value high
32-bit | 24
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 28
+ *
+----------------+----------------+----------------+----------------+
+ *
|/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/|
+ *
+----------------+----------------+----------------+----------------+
+ * | reserved | 64
+ *
+----------------+----------------+----------------+----------------+
+ *
+ * type - uint8_t, type of the control, one of the XENCAMERA_CTRL_XXX.
+ * value - int64_t, new value of the control.
+ *
+ * Notes:
+ * - this event is not sent for write-only controls
+ * - this event is not sent to the originator of the control change
+ * - this event is not sent when frontend first connects, e.g.
initial
+ * control state must be explicitly queried
+ */
+
+struct xencamera_req {
+ uint16_t id;
+ uint8_t operation;
+ uint8_t reserved[5];
+ union {
+ struct xencamera_config_req config;
+ struct xencamera_frame_rate_req frame_rate;
+ struct xencamera_buf_request buf_request;
+ struct xencamera_buf_create_req buf_create;
+ struct xencamera_index index;
+ struct xencamera_ctrl_value ctrl_value;
+ struct xencamera_get_ctrl_req get_ctrl;
+ uint8_t reserved[56];
+ } req;
+};
+
+struct xencamera_resp {
+ uint16_t id;
+ uint8_t operation;
+ uint8_t reserved;
+ int32_t status;
+ union {
+ struct xencamera_config_resp config;
+ struct xencamera_buf_get_layout_resp buf_layout;
+ struct xencamera_buf_request buf_request;
+ struct xencamera_ctrl_enum_resp ctrl_enum;
+ struct xencamera_ctrl_value ctrl_value;
+ uint8_t reserved1[56];
+ } resp;
+};
+
+struct xencamera_evt {
+ uint16_t id;
+ uint8_t type;
+ uint8_t reserved[5];
+ union {
+ struct xencamera_frame_avail_evt frame_avail;
+ struct xencamera_ctrl_value ctrl_value;
+ uint8_t reserved[56];
+ } evt;
+};
+
+DEFINE_RING_TYPES(xen_cameraif, struct xencamera_req, struct
xencamera_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 xencamera_event_page {
+ uint32_t in_cons;
+ uint32_t in_prod;
+ uint8_t reserved[56];
+};
+
+#define XENCAMERA_EVENT_PAGE_SIZE 4096
+#define XENCAMERA_IN_RING_OFFS (sizeof(struct xencamera_event_page))
+#define XENCAMERA_IN_RING_SIZE (XENCAMERA_EVENT_PAGE_SIZE -
XENCAMERA_IN_RING_OFFS)
+#define XENCAMERA_IN_RING_LEN (XENCAMERA_IN_RING_SIZE /
sizeof(struct xencamera_evt))
+#define XENCAMERA_IN_RING(page) \
+ ((struct xencamera_evt *)((char *)(page) +
XENCAMERA_IN_RING_OFFS))
+#define XENCAMERA_IN_RING_REF(page, idx) \
+ (XENCAMERA_IN_RING((page))[(idx) % XENCAMERA_IN_RING_LEN])
+
+#endif /* __XEN_PUBLIC_IO_CAMERAIF_H__ */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
Regards,
Hans
Thank you for your time,
Oleksandr
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