devices/src/virtio/video/mod.rs - platform/external/crosvm - Gitiles

 // Copyright 2020 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 //! This module implements the virtio video encoder and decoder devices.
 //! The current implementation uses [v3 RFC] of the virtio-video protocol.
 //!
 //! [v3 RFC]: https://markmail.org/thread/wxdne5re7aaugbjg

 use std::thread;

 #[cfg(feature = "video-encoder")]
 use base::info;
 use base::{error, AsRawDescriptor, Error as SysError, Event, RawDescriptor, Tube};
 use data_model::{DataInit, Le32};
 use remain::sorted;
 use thiserror::Error;
 use vm_memory::GuestMemory;

 use crate::virtio::virtio_device::VirtioDevice;
 use crate::virtio::{self, copy_config, DescriptorError, Interrupt};

 #[macro_use]
 mod macros;
 mod async_cmd_desc_map;
 mod command;
 mod control;
 #[cfg(feature = "video-decoder")]
 mod decoder;
 mod device;
 #[cfg(feature = "video-encoder")]
 mod encoder;
 mod error;
 mod event;
 mod format;
 mod params;
 mod protocol;
 mod resource;
 mod response;
 mod worker;

 #[cfg(all(feature = "video-decoder", not(feature = "libvda")))]
 compile_error!("The \"video-decoder\" feature requires \"libvda\" to also be enabled.");

 #[cfg(all(feature = "video-encoder", not(feature = "libvda")))]
 compile_error!("The \"video-encoder\" feature requires \"libvda\" to also be enabled.");

 #[cfg(feature = "libvda")]
 mod vda;

 use command::ReadCmdError;
 use device::Device;
 use worker::Worker;

 const QUEUE_SIZE: u16 = 256;
 const QUEUE_SIZES: &[u16] = &[QUEUE_SIZE, QUEUE_SIZE];

 /// An error indicating something went wrong in virtio-video's worker.
 #[sorted]
 #[derive(Error, Debug)]
 pub enum Error {
     /// No available descriptor in which an event is written to.
     #[error("no available descriptor in which an event is written to")]
     DescriptorNotAvailable,
     /// A DescriptorChain contains invalid data.
     #[error("DescriptorChain contains invalid data: {0}")]
     InvalidDescriptorChain(DescriptorError),
     /// Failed to read a virtio-video command.
     #[error("failed to read a command from the guest: {0}")]
     ReadFailure(ReadCmdError),
     /// Creating WaitContext failed.
     #[error("failed to create WaitContext: {0}")]
     WaitContextCreationFailed(SysError),
     /// Error while polling for events.
     #[error("failed to wait for events: {0}")]
     WaitError(SysError),
     /// Failed to write an event into the event queue.
     #[error("failed to write an event {event:?} into event queue: {error}")]
     WriteEventFailure {
         event: event::VideoEvt,
         error: std::io::Error,
     },
 }

 pub type Result<T> = std::result::Result<T, Error>;

 #[derive(Debug)]
 pub enum VideoDeviceType {
     #[cfg(feature = "video-decoder")]
     Decoder,
     #[cfg(feature = "video-encoder")]
     Encoder,
 }

 pub struct VideoDevice {
     device_type: VideoDeviceType,
     backend: VideoBackendType,
     kill_evt: Option<Event>,
     resource_bridge: Option<Tube>,
     base_features: u64,
 }

 impl VideoDevice {
     pub fn new(
         base_features: u64,
         device_type: VideoDeviceType,
         backend: VideoBackendType,
         resource_bridge: Option<Tube>,
     ) -> VideoDevice {
         VideoDevice {
             device_type,
             backend,
             kill_evt: None,
             resource_bridge,
             base_features,
         }
     }
 }

 impl Drop for VideoDevice {
     fn drop(&mut self) {
         if let Some(kill_evt) = self.kill_evt.take() {
             // Ignore the result because there is nothing we can do about it.
             let _ = kill_evt.write(1);
         }
     }
 }

 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum VideoBackendType {
     #[cfg(feature = "libvda")]
     Libvda,
 }

 impl VirtioDevice for VideoDevice {
     fn keep_rds(&self) -> Vec<RawDescriptor> {
         let mut keep_rds = Vec::new();
         if let Some(resource_bridge) = &self.resource_bridge {
             keep_rds.push(resource_bridge.as_raw_descriptor());
         }
         keep_rds
     }

     fn device_type(&self) -> u32 {
         match &self.device_type {
             #[cfg(feature = "video-decoder")]
             VideoDeviceType::Decoder => virtio::TYPE_VIDEO_DEC,
             #[cfg(feature = "video-encoder")]
             VideoDeviceType::Encoder => virtio::TYPE_VIDEO_ENC,
         }
     }

     fn queue_max_sizes(&self) -> &[u16] {
         QUEUE_SIZES
     }

     fn features(&self) -> u64 {
         self.base_features
             | 1u64 << protocol::VIRTIO_VIDEO_F_RESOURCE_NON_CONTIG
             | 1u64 << protocol::VIRTIO_VIDEO_F_RESOURCE_VIRTIO_OBJECT
     }

     fn read_config(&self, offset: u64, data: &mut [u8]) {
         let mut cfg = protocol::virtio_video_config {
             version: Le32::from(0),
             max_caps_length: Le32::from(1024), // Set a big number
             max_resp_length: Le32::from(1024), // Set a big number
         };
         copy_config(data, 0, cfg.as_mut_slice(), offset);
     }

     fn activate(
         &mut self,
         mem: GuestMemory,
         interrupt: Interrupt,
         mut queues: Vec<virtio::queue::Queue>,
         mut queue_evts: Vec<Event>,
     ) {
         if queues.len() != QUEUE_SIZES.len() {
             error!(
                 "wrong number of queues are passed: expected {}, actual {}",
                 queues.len(),
                 QUEUE_SIZES.len()
             );
             return;
         }
         if queue_evts.len() != QUEUE_SIZES.len() {
             error!(
                 "wrong number of events are passed: expected {}, actual {}",
                 queue_evts.len(),
                 QUEUE_SIZES.len()
             );
         }

         let (self_kill_evt, kill_evt) = match Event::new().and_then(|e| Ok((e.try_clone()?, e))) {
             Ok(v) => v,
             Err(e) => {
                 error!("failed to create kill Event pair: {:?}", e);
                 return;
             }
         };
         self.kill_evt = Some(self_kill_evt);

         let cmd_queue = queues.remove(0);
         let cmd_evt = queue_evts.remove(0);
         let event_queue = queues.remove(0);
         let event_evt = queue_evts.remove(0);
         let backend = self.backend;
         let resource_bridge = match self.resource_bridge.take() {
             Some(r) => r,
             None => {
                 error!("no resource bridge is passed");
                 return;
             }
         };
         let mut worker = Worker::new(
             interrupt,
             mem,
             cmd_queue,
             cmd_evt,
             event_queue,
             event_evt,
             kill_evt,
         );
         let worker_result = match &self.device_type {
             #[cfg(feature = "video-decoder")]
             VideoDeviceType::Decoder => thread::Builder::new()
                 .name("virtio video decoder".to_owned())
                 .spawn(move || {
                     let device: Box<dyn Device> = match backend {
                         #[cfg(feature = "libvda")]
                         VideoBackendType::Libvda => {
                             let vda = match decoder::backend::vda::LibvdaDecoder::new() {
                                 Ok(vda) => vda,
                                 Err(e) => {
                                     error!("Failed to initialize VDA for decoder: {}", e);
                                     return;
                                 }
                             };
                             Box::new(decoder::Decoder::new(vda, resource_bridge))
                         }
                     };

                     if let Err(e) = worker.run(device) {
                         error!("Failed to start decoder worker: {}", e);
                     };
                     // Don't return any information since the return value is never checked.
                 }),
             #[cfg(feature = "video-encoder")]
             VideoDeviceType::Encoder => thread::Builder::new()
                 .name("virtio video encoder".to_owned())
                 .spawn(move || {
                     let device: Box<dyn Device> = match backend {
                         #[cfg(feature = "libvda")]
                         VideoBackendType::Libvda => {
                             let vda = match encoder::backend::vda::LibvdaEncoder::new() {
                                 Ok(vda) => vda,
                                 Err(e) => {
                                     error!("Failed to initialize VDA for encoder: {}", e);
                                     return;
                                 }
                             };

                             match encoder::EncoderDevice::new(vda, resource_bridge) {
                                 Ok(encoder) => Box::new(encoder),
                                 Err(e) => {
                                     error!("Failed to create encoder device: {}", e);
                                     return;
                                 }
                             }
                         }
                     };

                     if let Err(e) = worker.run(device) {
                         error!("Failed to start encoder worker: {}", e);
                     }
                 }),
         };
         if let Err(e) = worker_result {
             error!(
                 "failed to spawn virtio_video worker for {:?}: {}",
                 &self.device_type, e
             );
             return;
         }
     }
 }

 /// Manages the zero-length, EOS-marked buffer signaling the end of a stream.
 ///
 /// Both the decoder and encoder need to signal end-of-stream events using a zero-sized buffer
 /// marked with the `VIRTIO_VIDEO_BUFFER_FLAG_EOS` flag. This struct allows to keep a buffer aside
 /// for that purpose.
 ///
 /// TODO(b/149725148): Remove this when libvda supports buffer flags.
 #[cfg(feature = "video-encoder")]
 struct EosBufferManager {
     stream_id: u32,
     eos_buffer: Option<u32>,
     client_awaits_eos: bool,
     responses: Vec<device::VideoEvtResponseType>,
 }

 #[cfg(feature = "video-encoder")]
 impl EosBufferManager {
     /// Create a new EOS manager for stream `stream_id`.
     fn new(stream_id: u32) -> Self {
         Self {
             stream_id,
             eos_buffer: None,
             client_awaits_eos: false,
             responses: Default::default(),
         }
     }

     /// Attempt to reserve buffer `buffer_id` for use as EOS buffer.
     ///
     /// This method should be called by the output buffer queueing code of the device. It returns
     /// `true` if the buffer has been kept aside for EOS, `false` otherwise (which means another
     /// buffer is already kept aside for EOS). If `true` is returned, the client must not use the
     /// buffer for any other purpose.
     fn try_reserve_eos_buffer(&mut self, buffer_id: u32) -> bool {
         let is_none = self.eos_buffer.is_none();

         if is_none {
             info!(
                 "stream {}: keeping buffer {} aside to signal EOS.",
                 self.stream_id, buffer_id
             );
             self.eos_buffer = Some(buffer_id);
         }

         is_none
     }

     /// Attempt to complete an EOS event using the previously reserved buffer, if available.
     ///
     /// `responses` is a vector of responses to be sent to the driver along with the EOS buffer. If
     /// an EOS buffer has been made available using the `try_reserve_eos_buffer` method, then this
     /// method returns the `responses` vector with the EOS buffer dequeue appended in first
     /// position.
     ///
     /// If no EOS buffer is available, then the contents of `responses` is put aside, and will be
     /// returned the next time this method is called with an EOS buffer available. When this
     /// happens, `client_awaits_eos` will be set to true, and the client can check this member and
     /// call this method again right after queuing the next buffer to obtain the EOS response as
     /// soon as is possible.
     fn try_complete_eos(
         &mut self,
         responses: Vec<device::VideoEvtResponseType>,
     ) -> Option<Vec<device::VideoEvtResponseType>> {
         let eos_buffer_id = self.eos_buffer.take().or_else(|| {
             info!("stream {}: no EOS resource available on successful flush response, waiting for next buffer to be queued.", self.stream_id);
             self.client_awaits_eos = true;
             if !self.responses.is_empty() {
                 error!("stream {}: EOS requested while one is already in progress. This is a bug!", self.stream_id);
             }
             self.responses = responses;
             None
         })?;

         let eos_tag = device::AsyncCmdTag::Queue {
             stream_id: self.stream_id,
             queue_type: command::QueueType::Output,
             resource_id: eos_buffer_id,
         };

         let eos_response = response::CmdResponse::ResourceQueue {
             timestamp: 0,
             flags: protocol::VIRTIO_VIDEO_BUFFER_FLAG_EOS,
             size: 0,
         };

         self.client_awaits_eos = false;

         info!(
             "stream {}: signaling EOS using buffer {}.",
             self.stream_id, eos_buffer_id
         );

         let mut responses = std::mem::take(&mut self.responses);
         responses.insert(
             0,
             device::VideoEvtResponseType::AsyncCmd(device::AsyncCmdResponse::from_response(
                 eos_tag,
                 eos_response,
             )),
         );

         Some(responses)
     }

     /// Reset the state of the manager, for use during e.g. stream resets.
     fn reset(&mut self) {
         self.eos_buffer = None;
         self.client_awaits_eos = false;
         self.responses.clear();
     }
 }
	// Copyright 2020 The Chromium OS Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	//! This module implements the virtio video encoder and decoder devices.
	//! The current implementation uses [v3 RFC] of the virtio-video protocol.
	//!
	//! [v3 RFC]: https://markmail.org/thread/wxdne5re7aaugbjg

	use std::thread;

	#[cfg(feature = "video-encoder")]
	use base::info;
	use base::{error, AsRawDescriptor, Error as SysError, Event, RawDescriptor, Tube};
	use data_model::{DataInit, Le32};
	use remain::sorted;
	use thiserror::Error;
	use vm_memory::GuestMemory;

	use crate::virtio::virtio_device::VirtioDevice;
	use crate::virtio::{self, copy_config, DescriptorError, Interrupt};

	#[macro_use]
	mod macros;
	mod async_cmd_desc_map;
	mod command;
	mod control;
	#[cfg(feature = "video-decoder")]
	mod decoder;
	mod device;
	#[cfg(feature = "video-encoder")]
	mod encoder;
	mod error;
	mod event;
	mod format;
	mod params;
	mod protocol;
	mod resource;
	mod response;
	mod worker;

	#[cfg(all(feature = "video-decoder", not(feature = "libvda")))]
	compile_error!("The \"video-decoder\" feature requires \"libvda\" to also be enabled.");

	#[cfg(all(feature = "video-encoder", not(feature = "libvda")))]
	compile_error!("The \"video-encoder\" feature requires \"libvda\" to also be enabled.");

	#[cfg(feature = "libvda")]
	mod vda;

	use command::ReadCmdError;
	use device::Device;
	use worker::Worker;

	const QUEUE_SIZE: u16 = 256;
	const QUEUE_SIZES: &[u16] = &[QUEUE_SIZE, QUEUE_SIZE];

	/// An error indicating something went wrong in virtio-video's worker.
	#[sorted]
	#[derive(Error, Debug)]
	pub enum Error {
	/// No available descriptor in which an event is written to.
	#[error("no available descriptor in which an event is written to")]
	DescriptorNotAvailable,
	/// A DescriptorChain contains invalid data.
	#[error("DescriptorChain contains invalid data: {0}")]
	InvalidDescriptorChain(DescriptorError),
	/// Failed to read a virtio-video command.
	#[error("failed to read a command from the guest: {0}")]
	ReadFailure(ReadCmdError),
	/// Creating WaitContext failed.
	#[error("failed to create WaitContext: {0}")]
	WaitContextCreationFailed(SysError),
	/// Error while polling for events.
	#[error("failed to wait for events: {0}")]
	WaitError(SysError),
	/// Failed to write an event into the event queue.
	#[error("failed to write an event {event:?} into event queue: {error}")]
	WriteEventFailure {
	event: event::VideoEvt,
	error: std::io::Error,
	},
	}

	pub type Result<T> = std::result::Result<T, Error>;

	#[derive(Debug)]
	pub enum VideoDeviceType {
	#[cfg(feature = "video-decoder")]
	Decoder,
	#[cfg(feature = "video-encoder")]
	Encoder,
	}

	pub struct VideoDevice {
	device_type: VideoDeviceType,
	backend: VideoBackendType,
	kill_evt: Option<Event>,
	resource_bridge: Option<Tube>,
	base_features: u64,
	}

	impl VideoDevice {
	pub fn new(
	base_features: u64,
	device_type: VideoDeviceType,
	backend: VideoBackendType,
	resource_bridge: Option<Tube>,
	) -> VideoDevice {
	VideoDevice {
	device_type,
	backend,
	kill_evt: None,
	resource_bridge,
	base_features,
	}
	}
	}

	impl Drop for VideoDevice {
	fn drop(&mut self) {
	if let Some(kill_evt) = self.kill_evt.take() {
	// Ignore the result because there is nothing we can do about it.
	let _ = kill_evt.write(1);
	}
	}
	}

	#[derive(Clone, Copy, Debug, PartialEq)]
	pub enum VideoBackendType {
	#[cfg(feature = "libvda")]
	Libvda,
	}

	impl VirtioDevice for VideoDevice {
	fn keep_rds(&self) -> Vec<RawDescriptor> {
	let mut keep_rds = Vec::new();
	if let Some(resource_bridge) = &self.resource_bridge {
	keep_rds.push(resource_bridge.as_raw_descriptor());
	}
	keep_rds
	}

	fn device_type(&self) -> u32 {
	match &self.device_type {
	#[cfg(feature = "video-decoder")]
	VideoDeviceType::Decoder => virtio::TYPE_VIDEO_DEC,
	#[cfg(feature = "video-encoder")]
	VideoDeviceType::Encoder => virtio::TYPE_VIDEO_ENC,
	}
	}

	fn queue_max_sizes(&self) -> &[u16] {
	QUEUE_SIZES
	}

	fn features(&self) -> u64 {
	self.base_features
	\| 1u64 << protocol::VIRTIO_VIDEO_F_RESOURCE_NON_CONTIG
	\| 1u64 << protocol::VIRTIO_VIDEO_F_RESOURCE_VIRTIO_OBJECT
	}

	fn read_config(&self, offset: u64, data: &mut [u8]) {
	let mut cfg = protocol::virtio_video_config {
	version: Le32::from(0),
	max_caps_length: Le32::from(1024), // Set a big number
	max_resp_length: Le32::from(1024), // Set a big number
	};
	copy_config(data, 0, cfg.as_mut_slice(), offset);
	}

	fn activate(
	&mut self,
	mem: GuestMemory,
	interrupt: Interrupt,
	mut queues: Vec<virtio::queue::Queue>,
	mut queue_evts: Vec<Event>,
	) {
	if queues.len() != QUEUE_SIZES.len() {
	error!(
	"wrong number of queues are passed: expected {}, actual {}",
	queues.len(),
	QUEUE_SIZES.len()
	);
	return;
	}
	if queue_evts.len() != QUEUE_SIZES.len() {
	error!(
	"wrong number of events are passed: expected {}, actual {}",
	queue_evts.len(),
	QUEUE_SIZES.len()
	);
	}

	let (self_kill_evt, kill_evt) = match Event::new().and_then(\|e\| Ok((e.try_clone()?, e))) {
	Ok(v) => v,
	Err(e) => {
	error!("failed to create kill Event pair: {:?}", e);
	return;
	}
	};
	self.kill_evt = Some(self_kill_evt);

	let cmd_queue = queues.remove(0);
	let cmd_evt = queue_evts.remove(0);
	let event_queue = queues.remove(0);
	let event_evt = queue_evts.remove(0);
	let backend = self.backend;
	let resource_bridge = match self.resource_bridge.take() {
	Some(r) => r,
	None => {
	error!("no resource bridge is passed");
	return;
	}
	};
	let mut worker = Worker::new(
	interrupt,
	mem,
	cmd_queue,
	cmd_evt,
	event_queue,
	event_evt,
	kill_evt,
	);
	let worker_result = match &self.device_type {
	#[cfg(feature = "video-decoder")]
	VideoDeviceType::Decoder => thread::Builder::new()
	.name("virtio video decoder".to_owned())
	.spawn(move \|\| {
	let device: Box<dyn Device> = match backend {
	#[cfg(feature = "libvda")]
	VideoBackendType::Libvda => {
	let vda = match decoder::backend::vda::LibvdaDecoder::new() {
	Ok(vda) => vda,
	Err(e) => {
	error!("Failed to initialize VDA for decoder: {}", e);
	return;
	}
	};
	Box::new(decoder::Decoder::new(vda, resource_bridge))
	}
	};

	if let Err(e) = worker.run(device) {
	error!("Failed to start decoder worker: {}", e);
	};
	// Don't return any information since the return value is never checked.
	}),
	#[cfg(feature = "video-encoder")]
	VideoDeviceType::Encoder => thread::Builder::new()
	.name("virtio video encoder".to_owned())
	.spawn(move \|\| {
	let device: Box<dyn Device> = match backend {
	#[cfg(feature = "libvda")]
	VideoBackendType::Libvda => {
	let vda = match encoder::backend::vda::LibvdaEncoder::new() {
	Ok(vda) => vda,
	Err(e) => {
	error!("Failed to initialize VDA for encoder: {}", e);
	return;
	}
	};

	match encoder::EncoderDevice::new(vda, resource_bridge) {
	Ok(encoder) => Box::new(encoder),
	Err(e) => {
	error!("Failed to create encoder device: {}", e);
	return;
	}
	}
	}
	};

	if let Err(e) = worker.run(device) {
	error!("Failed to start encoder worker: {}", e);
	}
	}),
	};
	if let Err(e) = worker_result {
	error!(
	"failed to spawn virtio_video worker for {:?}: {}",
	&self.device_type, e
	);
	return;
	}
	}
	}

	/// Manages the zero-length, EOS-marked buffer signaling the end of a stream.
	///
	/// Both the decoder and encoder need to signal end-of-stream events using a zero-sized buffer
	/// marked with the `VIRTIO_VIDEO_BUFFER_FLAG_EOS` flag. This struct allows to keep a buffer aside
	/// for that purpose.
	///
	/// TODO(b/149725148): Remove this when libvda supports buffer flags.
	#[cfg(feature = "video-encoder")]
	struct EosBufferManager {
	stream_id: u32,
	eos_buffer: Option<u32>,
	client_awaits_eos: bool,
	responses: Vec<device::VideoEvtResponseType>,
	}

	#[cfg(feature = "video-encoder")]
	impl EosBufferManager {
	/// Create a new EOS manager for stream `stream_id`.
	fn new(stream_id: u32) -> Self {
	Self {
	stream_id,
	eos_buffer: None,
	client_awaits_eos: false,
	responses: Default::default(),
	}
	}

	/// Attempt to reserve buffer `buffer_id` for use as EOS buffer.
	///
	/// This method should be called by the output buffer queueing code of the device. It returns
	/// `true` if the buffer has been kept aside for EOS, `false` otherwise (which means another
	/// buffer is already kept aside for EOS). If `true` is returned, the client must not use the
	/// buffer for any other purpose.
	fn try_reserve_eos_buffer(&mut self, buffer_id: u32) -> bool {
	let is_none = self.eos_buffer.is_none();

	if is_none {
	info!(
	"stream {}: keeping buffer {} aside to signal EOS.",
	self.stream_id, buffer_id
	);
	self.eos_buffer = Some(buffer_id);
	}

	is_none
	}

	/// Attempt to complete an EOS event using the previously reserved buffer, if available.
	///
	/// `responses` is a vector of responses to be sent to the driver along with the EOS buffer. If
	/// an EOS buffer has been made available using the `try_reserve_eos_buffer` method, then this
	/// method returns the `responses` vector with the EOS buffer dequeue appended in first
	/// position.
	///
	/// If no EOS buffer is available, then the contents of `responses` is put aside, and will be
	/// returned the next time this method is called with an EOS buffer available. When this
	/// happens, `client_awaits_eos` will be set to true, and the client can check this member and
	/// call this method again right after queuing the next buffer to obtain the EOS response as
	/// soon as is possible.
	fn try_complete_eos(
	&mut self,
	responses: Vec<device::VideoEvtResponseType>,
	) -> Option<Vec<device::VideoEvtResponseType>> {
	let eos_buffer_id = self.eos_buffer.take().or_else(\|\| {
	info!("stream {}: no EOS resource available on successful flush response, waiting for next buffer to be queued.", self.stream_id);
	self.client_awaits_eos = true;
	if !self.responses.is_empty() {
	error!("stream {}: EOS requested while one is already in progress. This is a bug!", self.stream_id);
	}
	self.responses = responses;
	None
	})?;

	let eos_tag = device::AsyncCmdTag::Queue {
	stream_id: self.stream_id,
	queue_type: command::QueueType::Output,
	resource_id: eos_buffer_id,
	};

	let eos_response = response::CmdResponse::ResourceQueue {
	timestamp: 0,
	flags: protocol::VIRTIO_VIDEO_BUFFER_FLAG_EOS,
	size: 0,
	};

	self.client_awaits_eos = false;

	info!(
	"stream {}: signaling EOS using buffer {}.",
	self.stream_id, eos_buffer_id
	);

	let mut responses = std::mem::take(&mut self.responses);
	responses.insert(
	0,
	device::VideoEvtResponseType::AsyncCmd(device::AsyncCmdResponse::from_response(
	eos_tag,
	eos_response,
	)),
	);

	Some(responses)
	}

	/// Reset the state of the manager, for use during e.g. stream resets.
	fn reset(&mut self) {
	self.eos_buffer = None;
	self.client_awaits_eos = false;
	self.responses.clear();
	}
	}