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Wed, 18 Dec 2019 17:29:42 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C80F8620DA; Wed, 18 Dec 2019 17:29:42 +0000 (UTC) Received: from zmail25.collab.prod.int.phx2.redhat.com (zmail25.collab.prod.int.phx2.redhat.com [10.5.83.31]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 51CC61803C32; Wed, 18 Dec 2019 17:29:42 +0000 (UTC) Date: Wed, 18 Dec 2019 12:29:40 -0500 (EST) From: Frediano Ziglio To: Keiichi Watanabe Cc: virtio-dev@lists.oasis-open.org, linux-media@vger.kernel.org, acourbot@chromium.org, alexlau@chromium.org, daniel@ffwll.ch, dgreid@chromium.org, dmitry sepp , egranata@google.com, hverkuil@xs4all.nl, kraxel@redhat.com, marcheu@chromium.org, posciak@chromium.org, spice-devel@lists.freedesktop.org, stevensd@chromium.org, tfiga@chromium.org, uril@redhat.com Message-ID: <718815324.16531975.1576690180746.JavaMail.zimbra@redhat.com> In-Reply-To: <20191218130214.170703-2-keiichiw@chromium.org> References: <20191218130214.170703-1-keiichiw@chromium.org> <20191218130214.170703-2-keiichiw@chromium.org> Subject: Re: [PATCH v2 1/1] virtio-video: Add virtio video device specification MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.33.32.29, 10.4.195.12] Thread-Topic: virtio-video: Add virtio video device specification Thread-Index: sv2iHEQPrGsY2WgvMxh5eGUyZHuveg== X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org > > From: Dmitry Sepp > > The virtio video encoder device and decoder device provide functionalities to > encode and decode video stream respectively. > Though video encoder and decoder are provided as different devices, they use > a > same protocol. > > Signed-off-by: Dmitry Sepp > Signed-off-by: Keiichi Watanabe > --- > content.tex | 1 + > virtio-video.tex | 579 +++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 580 insertions(+) > create mode 100644 virtio-video.tex > > diff --git a/content.tex b/content.tex > index 556b373..9e56839 100644 > --- a/content.tex > +++ b/content.tex > @@ -5743,6 +5743,7 @@ \subsubsection{Legacy Interface: Framing > Requirements}\label{sec:Device > \input{virtio-vsock.tex} > \input{virtio-fs.tex} > \input{virtio-rpmb.tex} > +\input{virtio-video.tex} > > \chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits} > > diff --git a/virtio-video.tex b/virtio-video.tex > new file mode 100644 > index 0000000..30e728d > --- /dev/null > +++ b/virtio-video.tex > @@ -0,0 +1,579 @@ > +\section{Video Device}\label{sec:Device Types / Video Device} > + > +The virtio video encoder device and decoder device are virtual devices that > +supports encoding and decoding respectively. Though the encoder and the > decoder > +are different devices, they use the same protocol. > + > +\subsection{Device ID}\label{sec:Device Types / Video Device / Device ID} > + > +\begin{description} > +\item[30] encoder device > +\item[31] decoder device > +\end{description} > + > +\subsection{Virtqueues}\label{sec:Device Types / Video Device / Virtqueues} > + > +\begin{description} > +\item[0] controlq - queue for sending control commands. > +\item[1] eventq - queue for sending events happened in the device. > +\end{description} > + > +\subsection{Feature bits}\label{sec:Device Types / Video Device / Feature > bits} > + > +\begin{description} > +\item[VIRTIO_VIDEO_F_RESOURCE_GUEST_PAGES (0)] Guest pages can be used for > video > + buffers. > +\end{description} > + > +\devicenormative{\subsubsection}{Feature bits}{Device Types / Video Device / > Feature bits} > + > +The device MUST offer at least one of feature bits. > + > +\subsection{Device configuration layout}\label{sec:Device Types / Video > Device / Device configuration layout} > + > +Video device configuration uses the following layout structure: > + > +\begin{lstlisting} > +struct virtio_video_config { > + le32 max_cap_len; > +}; > +\end{lstlisting} > + > +\begin{description} > +\item[\field{max_cap_len}] defines the maximum length of a descriptor > + required to call VIRTIO_VIDEO_GET_CAPABILITY in bytes. The device > + MUST set this value. > +\end{description} > + > +\subsection{Device Initialization}\label{sec:Device Types / Video Device / > Device Initialization} > + > +\devicenormative{\subsubsection}{Device Initialization}{Device Types / Video > Device / Device Initialization} > + > +The driver SHOULD query device capability by using the > +VIRTIO_VIDEO_T_GET_CAPABILITY and use that information for the initial > +setup. > + > +\subsection{Device Operation}\label{sec:Device Types / Video Device / Device > Operation} > + > +The driver allocates input and output buffers and queues the buffers > +to the device. The device performs operations on the buffers according > +to the function in question. > + > +\subsubsection{Device Operation: Create stream} > + > +To process buffers, the device needs to associate them with a certain > +video stream (essentially, a context). Streams are created by > +VIRTIO_VIDEO_T_STREAM_CREATE with a default set of parameters > +determined by the device. > + > +\subsubsection{Device Operation: Create buffers} > + > +Buffers are used to store the actual data as well as the relevant > +metadata. Scatter lists are supported, so the buffer doesn't need to > +be contiguous in guest physical memory. > + > +\begin{itemize*} > +\item Use VIRTIO_VIDEO_T_RESOURCE_CREATE to create a virtio video > + resource that is backed by a buffer allocated from the driver's > + memory. > +\item Use VIRTIO_VIDEO_T_RESOURCE_DESTROY to destroy a resource that > + is no longer needed. > +\end{itemize*} > + > +\subsubsection{Device Operation: Stream parameter control} > + > +\begin{itemize*} > +\item Use VIRTIO_VIDEO_T_GET_PARAMS to get the current stream parameters for > + input and output streams from the device. > +\item Use VIRTIO_VIDEO_T_SET_PARAMS to provide new stream parameters to the > + device. > +\item After setting stream parameters, the driver may issue > + VIRTIO_VIDEO_T_GET_PARAMS as some parameters of both input and output can > be > + changed implicitly by the device during the set operation. > +\end{itemize*} > + > +\subsubsection{Device Operation: Process buffers} > + > +\begin{itemize*} > +\item If the function and the buffer type require so, write data to > +the buffer memory. > +\item Use VIRTIO_VIDEO_T_RESOURCE_QUEUE to queue the buffer for > +processing in the device. > +\item The request completes asynchronously when the device has > +finished with the buffer. > +\end{itemize*} > + > +\subsubsection{Device Operation: Buffer processing control} > + > +\begin{itemize*} > +\item Use VIRTIO_VIDEO_T_STREAM_DRAIN to ask the device to process and > + return all of the already queued buffers. > +\item Use VIRTIO_VIDEO_T_QUEUE_CLEAR to ask the device to return back > + already queued buffers from the input or the output queue. This also > + includes input or output buffers that can be currently owned by the > + device's processing pipeline. > +\end{itemize*} > + > +\subsubsection{Device Operation: Asynchronous events} > + > +While processing buffers, the device can send asynchronous event > +notifications to the driver. The behaviour depends on the exact > +stream. For example, the decoder device sends a resolution change > +event when it encounters new resolution metadata in the stream. > + > +\subsubsection{Device Operation: Request header} > + > +All requests and responses on the control virt queue have a fixed > +header using the following layout structure and definitions: > + > +\begin{lstlisting} > +enum virtio_video_ctrl_type { > + VIRTIO_VIDEO_CTRL_UNDEFINED = 0, > + > + /* request */ > + VIRTIO_VIDEO_T_GET_CAPABILITY = 0x0100, > + VIRTIO_VIDEO_T_STREAM_CREATE, > + VIRTIO_VIDEO_T_STREAM_DESTROY, > + VIRTIO_VIDEO_T_STREAM_DRAIN, > + VIRTIO_VIDEO_T_RESOURCE_CREATE, > + VIRTIO_VIDEO_T_RESOURCE_DESTROY, > + VIRTIO_VIDEO_T_RESOURCE_QUEUE, > + VIRTIO_VIDEO_T_QUEUE_CLEAR, > + VIRTIO_VIDEO_T_SET_PARAMS, > + VIRTIO_VIDEO_T_GET_PARAMS, > + > + /* response */ > + VIRTIO_VIDEO_S_OK = 0x0200, > + VIRTIO_VIDEO_S_OK_RESOURCE_QUEUE, > + VIRTIO_VIDEO_S_OK_GET_PARAMS, > + > + VIRTIO_VIDEO_S_ERR_UNSPEC = 0x0300, > + VIRTIO_VIDEO_S_ERR_OUT_OF_MEMORY, > + VIRTIO_VIDEO_S_ERR_INVALID_RESOURCE_ID, > + VIRTIO_VIDEO_S_ERR_INVALID_STREAM_ID, > + VIRTIO_VIDEO_S_ERR_INVALID_PARAMETER, > +}; > + > +struct virtio_video_ctrl_hdr { > + le32 type; > + le32 stream_id; > + le32 len; /* Length of the structure in bytes. */ > +}; > +\end{lstlisting} > + > +\begin{description} > +\item[\field{type}] is the type of the driver request or the device > +response. > +\item[\field{stream_id}] specifies a target stream. > +\item[\field{len}] is the length of data in bytes, which includes > +length of the header. I suppose is implicit that it's the size of the container structure. > +\end{description} > + > +\subsubsection{Device Operation: controlq} > + > +\begin{description} > + > +\item[VIRTIO_VIDEO_T_GET_CAPABILITY] Retrieve information about > +supported formats. > + > +The driver uses \field{struct virtio_video_get_capability} to send a > +query request. > + > +\begin{lstlisting} > +enum virtio_video_buf_type { > + VIRTIO_VIDEO_BUF_TYPE_INPUT, > + VIRTIO_VIDEO_BUF_TYPE_OUTPUT, > +}; > + > +struct virtio_video_get_capability { > + struct virtio_video_ctrl_hdr hdr; > + enum virtio_video_buf_type buf_type; Here you used an enumeration but later you are using just le32 type with a comment. Why this difference? > +}; > +\end{lstlisting} > +\begin{description} > +\item[\field{buf_type}] is the buffer type that the driver asks > +information about. The driver MUST set either > +\field{VIRTIO_VIDEO_BUF_TYPE_INPUT} or \field{VIRTIO_VIDEO_BUF_TYPE_OUTPUT}. > +\end{description} > + > +The device responds a capability by using \field{struct > +virtio_video_get_capability_resp}. > +\begin{lstlisting} > +enum virtio_video_format { > + VIRTIO_VIDEO_FORMAT_UNDEFINED = 0, Really minor: maybe you want to insert an empty line to be coherent with other enumerations? > + /* Raw formats */ > + VIRTIO_VIDEO_FORMAT_NV12 = 1, > + VIRTIO_VIDEO_FORMAT_YUV420, > + VIRTIO_VIDEO_FORMAT_YVU420, > + > + /* Compressed formats */ > + VIRTIO_VIDEO_FORMAT_H264 = 0x1001, > + VIRTIO_VIDEO_FORMAT_VP8 = 0x1002, > + VIRTIO_VIDEO_FORMAT_VP9 = 0x1003, > +}; > + > +enum virtio_video_profile { > + VIRTIO_VIDEO_PROFILE_UNDEFINED = 0, > + > + /* H.264 */ > + VIRTIO_VIDEO_PROFILE_H264_MIN = 0x100, > + VIRTIO_VIDEO_PROFILE_H264_BASELINE = > VIRTIO_VIDEO_PROFILE_H264_BASELINE, Maybe you want VIRTIO_VIDEO_PROFILE_H264_BASELINE = VIRTIO_VIDEO_PROFILE_H264_MIN, like others? > + VIRTIO_VIDEO_PROFILE_H264_MAIN, > + VIRTIO_VIDEO_PROFILE_H264_EXTENDED, > + VIRTIO_VIDEO_PROFILE_H264_HIGH, > + VIRTIO_VIDEO_PROFILE_H264_HIGH10PROFILE, > + VIRTIO_VIDEO_PROFILE_H264_HIGH422PROFILE, > + VIRTIO_VIDEO_PROFILE_H264_HIGH444PREDICTIVEPROFILE, > + VIRTIO_VIDEO_PROFILE_H264_SCALABLEBASELINE, > + VIRTIO_VIDEO_PROFILE_H264_SCALABLEHIGH, > + VIRTIO_VIDEO_PROFILE_H264_STEREOHIGH, > + VIRTIO_VIDEO_PROFILE_H264_MULTIVIEWHIGH, > + VIRTIO_VIDEO_PROFILE_H264_MAX = > VIRTIO_VIDEO_PROFILE_H264_MULTIVIEWHIGH, > + > + /* VP8 */ > + VIRTIO_VIDEO_PROFILE_VP8_MIN = 0x200, > + VIRTIO_VIDEO_PROFILE_VP8_ANY = VIRTIO_VIDEO_PROFILE_VP8_MIN, > + VIRTIO_VIDEO_PROFILE_VP8_MAX = VIRTIO_VIDEO_PROFILE_VP8_ANY, > + > + /* VP9 */ > + VIRTIO_VIDEO_PROFILE_VP9_MIN = 0x300, > + VIRTIO_VIDEO_PROFILE_VP9_PROFILE0 = VIRTIO_VIDEO_PROFILE_VP9_MIN, > + VIRTIO_VIDEO_PROFILE_VP9_PROFILE1, > + VIRTIO_VIDEO_PROFILE_VP9_PROFILE2, > + VIRTIO_VIDEO_PROFILE_VP9_PROFILE3, > + VIRTIO_VIDEO_PROFILE_VP9_MAX = VIRTIO_VIDEO_PROFILE_VP9_PROFILE3, > +}; > + > +struct virtio_video_format_range { > + le32 min; > + le32 max; > + le32 step; > + u8 paddings[4]; Here you padded at 8-byte like many other structures but not for virtio_video_ctrl_hdr. Is this expected? > +}; > + > +struct virtio_video_format_desc { > + le32 format; /* One of VIRTIO_VIDEO_FORMAT_* types */ > + le32 profile; /* One of VIRTIO_VIDEO_PROFILE_* types */ > + le64 mask; This will limit the formats to 64 while "num_descs" below is a 32 bit. > + struct virtio_video_format_range width; > + struct virtio_video_format_range height; > + le32 num_rates; > + u8 padding[4]; > + /* Followed by struct virtio_video_frame_rate frame_rates[] */ > +}; > + > +struct virtio_video_get_capability_resp { > + struct virtio_video_ctrl_hdr hdr; > + le32 num_descs; > + /* Followed by struct virtio_video_format_desc desc[] */ > +}; > +\end{lstlisting} > + > +The format description \field{struct virtio_video_format_desc} > +includes the following fields: > +\begin{description} > +\item[\field{format}] specifies an image format. The device MUST set one > + of \field{enum virtio_video_format}. > +\item[\field{profile}] specifies a profile of the compressed image format > + specified in \field{format}. The driver SHOULD ignore this value if > + \field{format} is a raw format. Why not documenting that MUST be VIRTIO_VIDEO_PROFILE_UNDEFINED for raw formats so the field could be extended in the future? > +\item[\field{mask}] is a bitset that represents the supported > + combination of input and output format. If \textit{i}-th bit is set > + in \field{mask} of \textit{j}-th \field{struct > + virtio_video_format_desc} for input, the device supports encoding or > + decoding from the \textit{j}-th input format to \textit{i}-th output > + format. > +\item[\field{width, height}] represents a range of resolutions > + supported by the device. If its \field{step} is not applicable, its > + \field{min} is equal to its \field{max}. > +\item[\field{num_rates}] is the length of an array \field{frame_rates}. In > case of decoder, the driver SHOULD ignore this value. > +\item[\field{frame_rates}] is an array of supported frame rates. I suppose here we are talking about bitrates, right? Could be confused by FPS. > +\end{description} > + > +\item[VIRTIO_VIDEO_T_STREAM_CREATE] create a video stream (context) > + within the device. > + > +\begin{lstlisting} > +enum virtio_video_mem_type { > + VIRTIO_VIDEO_MEM_TYPE_GUEST_PAGES, > +}; > + > +struct virtio_video_stream_create { > + struct virtio_video_ctrl_hdr hdr; > + le32 in_mem_type; /* One of VIRTIO_VIDEO_MEM_TYPE_* types */ > + le32 out_mem_type; /* One of VIRTIO_VIDEO_MEM_TYPE_* types */ > + char debug_name[64]; > +}; This structure has a size not multiple of 8-bytes. Not an issue, but the same apply to other structures that instead are padded to 8-byte size. > +\end{lstlisting} > + > +\begin{description} > +\item[\field{in_mem_type}] is a type of buffer management for input > +buffers. The driver MUST set a value in \field{enum > +virtio_video_mem_type}. > +\item[\field{out_mem_type}] is a type of buffer management for output > +buffers. The driver MUST set a value in \field{enum > +virtio_video_mem_type}. > +\item[\field{debug_name}] is a text string for a debug purpose. Must be NUL-terminated ? UTF-8 ? > +\end{description} > + > +\item[VIRTIO_VIDEO_T_STREAM_DESTROY] destroy a video stream (context) > + within the device. > + > +\begin{lstlisting} > +struct virtio_video_stream_destroy { > + struct virtio_video_ctrl_hdr hdr; > +}; > +\end{lstlisting} > + > +\item[VIRTIO_VIDEO_T_STREAM_DRAIN] ask the device to push all the > + queued buffers through the pipeline. > + > +\begin{lstlisting} > +struct virtio_video_stream_drain { > + struct virtio_video_ctrl_hdr hdr; > +}; > +\end{lstlisting} > + > +\item[VIRTIO_VIDEO_T_RESOURCE_CREATE] create a resource descriptor > + within the device. > + > +\begin{lstlisting} > +struct virtio_video_mem_entry { > + le64 addr; > + le32 length; > + u8 padding[4]; > +}; > + > +struct virtio_video_resource_create { > + struct virtio_video_ctrl_hdr hdr; > + le32 resource_id; > + le32 nr_entries; > +}; > +\end{lstlisting} > + > +\begin{description} > +\item[\field{resource_id}] internal id of the resource. Is it input or output? > +\item[\field{nr_entries}] number of \field{struct > + virtio_video_mem_entry} memory entries. I suppose that the structure is followed by an array of virtio_video_mem_entry after a padding of 4-bytes for alignment. > +\end{description} > + > +\item[VIRTIO_VIDEO_T_RESOURCE_DESTROY] destroy a resource descriptor > + within the device. > + > +\begin{lstlisting} > +struct virtio_video_resource_destroy { > + struct virtio_video_ctrl_hdr hdr; > + le32 resource_id; > + u8 padding[4]; Is this padding for future extensions? > +}; > +\end{lstlisting} > + > +\begin{description} > +\item[\field{resource_id}] internal id of the resource. > +\end{description} > + > +\item[VIRTIO_VIDEO_T_RESOURCE_QUEUE] Add a buffer to the device's > +queue. > + > +\begin{lstlisting} > +#define VIRTIO_VIDEO_MAX_PLANES 8 > + > +struct virtio_video_resource_queue { > + struct virtio_video_ctrl_hdr hdr; > + le32 buf_type; > + le32 resource_id; > + le64 timestamp; I suppose you would like this field aligned to avoid hidden paddings. > + le32 nr_data_size; > + le32 data_size[VIRTIO_VIDEO_MAX_PLANES]; > +}; > +\end{lstlisting} > + > +\begin{description} > +\item[\field{buf_type}] buf_type of the . > +\item[\field{resource_id}] internal id of the resource. > +\item[\field{timestamp}] an abstract sequence counter that can be used > + for synchronisation. > +\item[\field{nr_data_size}] number of \field{data_size} entries. > +\item[\field{data_size}] number of data bytes within a plane. > +\end{description} > + ... omissis ... > -- > 2.24.1.735.g03f4e72817-goog > > Frediano