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Subject: Re: [PATCH v2 1/1] virtio-video: Add virtio video device specification
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Hi Keiichi,
On Freitag, 20. Dezember 2019 16:26:50 CET Keiichi Watanabe wrote: > Hi Dmitry, > Thanks for the feedback. > > On Thu, Dec 19, 2019 at 10:28 PM Dmitry Sepp > > <dmitry.sepp@opensynergy.com> wrote: > > Hi Keiichi, > > > > Thank you for the update. Please see some comments below. > > > > Also, we need to bring the virtio_video_control back as it is in fact used > > by the driver to enumerate supported encoder controls. But yes, it still > > needs to be documemnted, it's true. > > Yeah, we need it eventually, but I'm wondering what is the difference > between values set by SET_PARAMS and ones by controls. > I saw your driver implementation has BITRATE, PROFILE and LEVEL as > controls. What's the reason why you didn't add them in > virtio_video_params? >
In fact I think the reasons was not to blow up the params structure. Also, virtio_video_param is used to inform the driver about the supported controls, very much like frame_formats, frame_sizes and so on. But for setting we probably can use the set_params structure, right.
> > On Mittwoch, 18. Dezember 2019 14:02:14 CET Keiichi Watanabe wrote: > > > From: Dmitry Sepp <dmitry.sepp@opensynergy.com> > > > > > > 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 <dmitry.sepp@opensynergy.com> > > > Signed-off-by: Keiichi Watanabe <keiichiw@chromium.org> > > > --- > > > > > > 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. > > > +\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, > > > +}; > > > > I personally didn't like the previous term: pin_type. But, to be honest, I > > don't like the buf_type neither. Consider the GET/SET_PARAMS request: > > buf_type there looks a bit unnatural. We are trying to get stream > > parameters there, not some parameters of whatever buffer. Also I don't > > see any strict reason to mimic v4l2 naming scheme. > > > > I'd better rename it to PORT_TYPE or QUEUE_TYPE. > > To be honest, I also wasn't satisfied with the name "buf_type". > QUEUE_TYPE sounds better. > Will rename it. > > > > + > > > +struct virtio_video_get_capability { > > > + struct virtio_video_ctrl_hdr hdr; > > > + enum virtio_video_buf_type buf_type; > > > +}; > > > +\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, > > > + /* Raw formats */ > > > + VIRTIO_VIDEO_FORMAT_NV12 = 1, > > > + VIRTIO_VIDEO_FORMAT_YUV420, > > > + VIRTIO_VIDEO_FORMAT_YVU420, > > > > Let's add some variants of RGB, like RGBA, ARGB. We need it for the > > encoder in particular . > > Sounds good. > BTW, which "ARGB8888" or "A8R8G8B8" is preferred? While the first one > comes from DRM's FourCC, the second one comes from virtio_gpu_formats. > I personally prefer the first one, then we can have a naming convention > like: VIRTIO_VIDEO_FORMAT_<name from drm_fourcc.h> >
I'd go with ARGB8888 and BGRA8888 (might be with X variants).
Best regards, Dmitry.
> > > + > > > + /* Compressed formats */ > > > + VIRTIO_VIDEO_FORMAT_H264 = 0x1001, > > > + VIRTIO_VIDEO_FORMAT_VP8 = 0x1002, > > > + VIRTIO_VIDEO_FORMAT_VP9 = 0x1003, > > > > Let's add H265, MPEG4, MPEG2. We already support and use them. > > Sure. > > Best regards, > Keiichi > > > Regards, > > Dmitry. > > > > > +}; > > > + > > > +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, + > > > 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]; > > > +}; > > > + > > > +struct virtio_video_format_desc { > > > + le32 format; /* One of VIRTIO_VIDEO_FORMAT_* types */ > > > + le32 profile; /* One of VIRTIO_VIDEO_PROFILE_* types */ > > > + le64 mask; > > > + 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. > > > +\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. > > > +\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]; > > > +}; > > > +\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. > > > +\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. > > > +\item[\field{nr_entries}] number of \field{struct > > > + virtio_video_mem_entry} memory entries. > > > +\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]; > > > +}; > > > +\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; > > > + 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} > > > + > > > +\begin{lstlisting} > > > +enum virtio_video_buffer_flag { > > > + VIRTIO_VIDEO_BUFFER_F_ERR = 0x0001, > > > + VIRTIO_VIDEO_BUFFER_F_EOS = 0x0002, > > > + /* Encoder only */ > > > + VIRTIO_VIDEO_BUFFER_IFRAME = 0x0004, > > > + VIRTIO_VIDEO_BUFFER_PFRAME = 0x0008, > > > + VIRTIO_VIDEO_BUFFER_BFRAME = 0x0010, > > > +}; > > > + > > > +struct virtio_video_resource_queue_resp { > > > + struct virtio_video_ctrl_hdr hdr; > > > + le64 timestamp; > > > + le32 flags; /* One of VIRTIO_VIDEO_BUFFER_* flags */ > > > + le32 size; /* Encoded size */ > > > +}; > > > +\end{lstlisting} > > > + > > > +\begin{description} > > > +\item[\field{timestamp}] an abstract sequence counter that can be used > > > + for synchronisation. > > > +\item[\field{flags}] mark specific buffers in the sequence. > > > +\item[\field{size}] data size in the buffer (encoder only). > > > +\end{description} > > > + > > > +The device sends a response to the queue request asynchronously when > > > +it has finished processing the buffer. > > > + > > > +The device SHOULD mark a buffer that triggered a processing error with > > > +the VIRTIO_VIDEO_BUFFER_F_ERR flag. > > > + > > > +The device MUST mark the last buffer with the > > > +VIRTIO_VIDEO_BUFFER_F_EOS flag to denote completion of the drain > > > +sequence. > > > + > > > +In case of encoder, to denote a particular frame type the devie MUST > > > +mark the respective buffer with VIRTIO_VIDEO_BUFFER_IFRAME, > > > +VIRTIO_VIDEO_BUFFER_PFRAME, VIRTIO_VIDEO_BUFFER_BFRAME. > > > + > > > +\item[VIRTIO_VIDEO_T_RESOURCE_QUEUE_CLEAR] Return already queued > > > + buffers back from the input or the output queue of the device. The > > > + device SHOULD return all of the buffers from the respective queue as > > > + soon as possible without pushing the buffers through the processing > > > + pipeline. > > > + > > > +\begin{lstlisting} > > > +struct virtio_video_queue_clear { > > > + struct virtio_video_ctrl_hdr hdr; > > > + le32 buf_type; > > > + u8 padding[4]; > > > +}; > > > +\end{lstlisting} > > > + > > > +\begin{description} > > > +\item[\field{buf_type}] buffer type. > > > +\end{description} > > > + > > > +\item[VIRTIO_VIDEO_T_GET_PARAMS] Get parameters of the input or the > > > + output of a stream. > > > + > > > +\begin{lstlisting} > > > +struct virtio_video_plane_format { > > > + le32 plane_size; > > > + le32 stride; > > > + u8 padding[4]; > > > +}; > > > +\end{lstlisting} > > > + > > > +\begin{description} > > > +\item[\field{plane_size}] size of the plane in bytes. > > > +\item[\field{stride}] stride used for the plane in bytes. > > > +\end{description} > > > + > > > +\begin{lstlisting} > > > +struct virtio_video_params { > > > + le32 buf_type; /* One of VIRTIO_VIDEO_BUF_TYPE_* types */ > > > + le32 fourcc; /* One of VIRTIO_VIDEO_FOURCC_* types */ > > > + le32 frame_width; > > > + le32 frame_height; > > > + le32 min_buffers; > > > + le32 max_buffers; > > > + le32 frame_rate; > > > + struct virtio_video_crop { > > > + le32 left; > > > + le32 top; > > > + le32 width; > > > + le32 height; > > > + } crop; > > > + le32 num_planes; > > > + struct virtio_video_plane_format > > > plane_formats[VIRTIO_VIDEO_MAX_PLANES]; +}; > > > +\end{lstlisting} > > > + > > > +\begin{description} > > > +\item[\field{frame_width}] the value to get/set. > > > +\item[\field{frame_height}] the value to get/set. > > > +\item[\field{pixel_format}] the value to get/set. > > > +\item[\field{min_buffers}] minimum buffers required to handle the > > > + format (r/o). > > > +\item[\field{max_buffers}] maximum buffers required to handle the > > > + format (r/o). > > > +\item[\field{frame_rate}] the value to get/set. > > > +\item[\field{crop}] cropping (composing) rectangle. > > > +\item[\field{num_planes}] number of planes used to store pixel data > > > +(r/o). > > > +\item[\field{plane_formats}] description of each plane. > > > +\end{description} > > > + > > > +\begin{lstlisting} > > > +struct virtio_video_get_params { > > > + struct virtio_video_ctrl_hdr hdr; > > > + le32 buf_type; /* One of VIRTIO_VIDEO_BUF_TYPE_* types */ > > > +}; > > > + > > > +struct virtio_video_get_params_resp { > > > + struct virtio_video_ctrl_hdr hdr; > > > + struct virtio_video_params params; > > > +}; > > > +\end{lstlisting} > > > + > > > +\begin{description} > > > +\item[\field{buf_type}] buffer type. > > > +\item[\field{params}] parameter values. > > > +\end{description} > > > + > > > +\item[VIRTIO_VIDEO_T_SET_PARAMS] Change parameters of a stream. > > > + > > > + > > > +\begin{lstlisting} > > > +struct virtio_video_set_params { > > > + struct virtio_video_ctrl_hdr hdr; > > > + struct virtio_video_params params; > > > +}; > > > +\end{lstlisting} > > > + > > > +\begin{description} > > > +\item[\field{params}] parameters to set. > > > +\end{description} > > > + > > > +Setting stream parameters might have side effects within the device. > > > +For example, the device MAY perform alignment of width and height, > > > +change the number of planes it uses for the format, or do whatever > > > +changes that are required to continue normal operation using the > > > +updated parameters. It is up to the driver to check the parameter set > > > +after the VIRTIO_VIDEO_T_SET_PARAMS request has been issued. > > > + > > > +\end{description} > > > + > > > +\subsubsection{Device Operation: eventq} > > > + > > > +The device can report events on the event queue. The driver initially > > > +populates the queue with device-writeable buffers. When the device > > > +needs to report an event, it fills a buffer and notifies the driver. > > > +The driver consumes the report and adds a new buffer to the virtqueue. > > > + > > > +\begin{lstlisting} > > > +enum virtio_video_event_type { > > > + VIRTIO_VIDEO_EVENT_T_UNDEFINED = 0, > > > + /* For all functions */ > > > + VIRTIO_VIDEO_EVENT_T_ERROR_UNSPEC = 0x0100, > > > + /* For decoder only */ > > > + VIRTIO_VIDEO_EVENT_T_DECODER_RESOLUTION_CHANGED = 0x0200, > > > +}; > > > + > > > +struct virtio_video_event { > > > + le32 event_type; /* One of VIRTIO_VIDEO_EVENT_T_* types */ > > > + le32 stream_id; > > > + u8 padding[4]; > > > +}; > > > +\end{lstlisting} > > > + > > > +\begin{description} > > > +\item[\field{event_type}] type of the triggered event . > > > +\item[\field{stream_id}] id of the source stream. > > > +\end{description} > > > + > > > +The device MUST send VIRTIO_VIDEO_EVENT_T_DECODER_RESOLUTION_CHANGED > > > +whenever it encounters new resolution data in the stream. This > > > +includes the case of the initial device configuration after metadata > > > +has been parsed and the case of dynamic resolution change. |
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