On Mon, Jan 08, 2024 at 06:18:50PM +0100, Mikhail Golubev-Ciuchea wrote: > Hi all! > > I kindly request a vote. > > Fixes: https://github.com/oasis-tcs/virtio-spec/issues/186 > > > Best wishes, > Mikhail Golubev-Ciuchea > > > > On 6/9/23 16:22, Mikhail Golubev-Ciuchea wrote: > > From: Harald Mommer <harald.mommer@xxxxxxxxxxxxxxx> > > > > virtio-can is a virtual CAN device. It provides a way to give access to > > a CAN controller from a driver guest. The device is aimed to be used by > > driver guests running a HLOS as well as by driver guests running a > > typical RTOS as used in controller environments. > > > > Signed-off-by: Harald Mommer <Harald.Mommer@xxxxxxxxxxxxxxx> > > Signed-off-by: Mikhail Golubev-Ciuchea <Mikhail.Golubev-Ciuchea@xxxxxxxxxxxxxxx> > > --- > > > > RFC v3: > > * Add length fields in CAN RX and TX messages. > > * Replace bus off indication queue with a config space bit. > > * Clarify handling of unknown flag bits set in CAN frame. > > * Remove MISRA C suffixes in constants. > > * Reserve 16 bits in RX/TX messages for CAN XL priority. > > * Reserve 8 bits in RX/TX messages for CAN classic DLC. > > * Rework according to general virtio spec POV. > > * Implementation: > > driver: https://lore.kernel.org/all/20230607145613.133203-1-Mikhail.Golubev-Ciuchea@xxxxxxxxxxxxxxx/ > > QEmu device: https://github.com/OpenSynergy/qemu/tree/virtio-can-spec-rfc-v3 > > > > RFC v2: > > * Add CAN classic feature flag. > > * Add feature flag VIRTIO_CAN_F_LATE_TX_ACK. > > * Add feature flag VIRTIO_CAN_F_RTR_FRAMES. > > * Reserve 32 bits in RX/TX messages. > > * Remove priorities of messages. > > > > conformance.tex | 12 +- > > content.tex | 1 + > > device-types/can/description.tex | 249 ++++++++++++++++++++++++ > > device-types/can/device-conformance.tex | 8 + > > device-types/can/driver-conformance.tex | 7 + > > introduction.tex | 2 + > > 6 files changed, 275 insertions(+), 4 deletions(-) > > create mode 100644 device-types/can/description.tex > > create mode 100644 device-types/can/device-conformance.tex > > create mode 100644 device-types/can/driver-conformance.tex > > > > diff --git a/conformance.tex b/conformance.tex > > index 01ccd69..a07ef02 100644 > > --- a/conformance.tex > > +++ b/conformance.tex > > @@ -32,8 +32,9 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} > > \ref{sec:Conformance / Driver Conformance / Memory Driver Conformance}, > > \ref{sec:Conformance / Driver Conformance / I2C Adapter Driver Conformance}, > > \ref{sec:Conformance / Driver Conformance / SCMI Driver Conformance}, > > -\ref{sec:Conformance / Driver Conformance / GPIO Driver Conformance} or > > -\ref{sec:Conformance / Driver Conformance / PMEM Driver Conformance}. > > +\ref{sec:Conformance / Driver Conformance / GPIO Driver Conformance}, > > +\ref{sec:Conformance / Driver Conformance / PMEM Driver Conformance} or > > +\ref{sec:Conformance / Driver Conformance / CAN Driver Conformance}. > > \item Clause \ref{sec:Conformance / Legacy Interface: Transitional Device and Transitional Driver Conformance}. > > \end{itemize} > > @@ -59,8 +60,9 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} > > \ref{sec:Conformance / Device Conformance / Memory Device Conformance}, > > \ref{sec:Conformance / Device Conformance / I2C Adapter Device Conformance}, > > \ref{sec:Conformance / Device Conformance / SCMI Device Conformance}, > > -\ref{sec:Conformance / Device Conformance / GPIO Device Conformance} or > > -\ref{sec:Conformance / Device Conformance / PMEM Device Conformance}. > > +\ref{sec:Conformance / Device Conformance / GPIO Device Conformance}, > > +\ref{sec:Conformance / Device Conformance / PMEM Device Conformance} or > > +\ref{sec:Conformance / Device Conformance / CAN Device Conformance}. > > \item Clause \ref{sec:Conformance / Legacy Interface: Transitional Device and Transitional Driver Conformance}. > > \end{itemize} > > @@ -152,6 +154,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} > > \input{device-types/scmi/driver-conformance.tex} > > \input{device-types/gpio/driver-conformance.tex} > > \input{device-types/pmem/driver-conformance.tex} > > +\input{device-types/can/driver-conformance.tex} > > \conformance{\section}{Device Conformance}\label{sec:Conformance / Device Conformance} > > @@ -238,6 +241,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} > > \input{device-types/scmi/device-conformance.tex} > > \input{device-types/gpio/device-conformance.tex} > > \input{device-types/pmem/device-conformance.tex} > > +\input{device-types/can/device-conformance.tex} > > \conformance{\section}{Legacy Interface: Transitional Device and Transitional Driver Conformance}\label{sec:Conformance / Legacy Interface: Transitional Device and Transitional Driver Conformance} > > A conformant implementation MUST be either transitional or > > diff --git a/content.tex b/content.tex > > index d2ab9eb..8806b57 100644 > > --- a/content.tex > > +++ b/content.tex > > @@ -765,6 +765,7 @@ \chapter{Device Types}\label{sec:Device Types} > > \input{device-types/scmi/description.tex} > > \input{device-types/gpio/description.tex} > > \input{device-types/pmem/description.tex} > > +\input{device-types/can/description.tex} > > \chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits} > > diff --git a/device-types/can/description.tex b/device-types/can/description.tex > > new file mode 100644 > > index 0000000..2511d9c > > --- /dev/null > > +++ b/device-types/can/description.tex > > @@ -0,0 +1,249 @@ > > +\section{CAN Device}\label{sec:Device Types / CAN Device} > > + > > +virtio-can is a virtio based CAN (Controller Area Network) controller. > > +It is used to give a virtual machine access to a CAN bus. The CAN bus > > +might either be a physical CAN bus or a virtual CAN bus between virtual > > +machines or a combination of both. > > + > > +\subsection{Device ID}\label{sec:Device Types / CAN Device / Device ID} > > + > > +36 > > + > > +\subsection{Virtqueues}\label{sec:Device Types / CAN Device / Virtqueues} > > + > > +\begin{description} > > +\item[0] Txq > > +\item[1] Rxq > > +\item[2] Controlq > > +\end{description} > > + > > +The \field{Txq} is used to send CAN packets to the CAN bus. > > + > > +The \field{Rxq} is used to receive CAN packets from the CAN bus. > > + > > +The \field{Controlq} is used to control the state of the CAN controller. > > + > > +\subsection{Feature bits}{Device Types / CAN Device / Feature bits} > > + > > +Actual CAN controllers support Extended CAN IDs with 29 bits (CAN~2.0B) > > +as well as Standard CAN IDs with 11 bits (CAN~2.0A). The support of > > +CAN~2.0B Extended CAN IDs is considered as mandatory for this > > +specification. > > + > > +\begin{description} > > + > > +\item[VIRTIO_CAN_F_CAN_CLASSIC (0)] > > + > > +The device supports classic CAN frames with a maximum payload size of 8 > > +bytes. > > + > > +\item[VIRTIO_CAN_F_CAN_FD (1)] > > + > > +The device supports CAN FD frames with a maximum payload size of 64 > > +bytes. > > + > > +\item[VIRTIO_CAN_F_RTR_FRAMES (2)] > > + > > +The device supports RTR (remote transmission request) frames. RTR frames > > +are only supported with classic CAN. > > + > > +\item[VIRTIO_CAN_F_LATE_TX_ACK (3)] > > + > > +The virtio CAN device marks transmission requests from the \field{Txq} > > +as used after the CAN message has been transmitted on the CAN bus. If > > +this feature bit has not been negotiated, the device is allowed to mark > > +transmission requests already as used when the CAN message has been > > +scheduled for transmission but might not yet have been transmitted on > > +the CAN bus. > > + > > +\end{description} > > + > > +\subsubsection{Feature bit requirements}\label{sec:Device Types / CAN Device / Feature bits / Feature bit requirements} > > + > > +Some CAN feature bits require other CAN feature bits: > > +\begin{description} > > +\item[VIRTIO_CAN_F_RTR_FRAMES] Requires VIRTIO_CAN_F_CAN_CLASSIC. > > +\end{description} > > + > > +It is required that at least one of VIRTIO_CAN_F_CAN_CLASSIC and > > +VIRTIO_CAN_F_CAN_FD is negotiated. > > + > > +\subsection{Device configuration layout}\label{sec:Device Types / CAN Device / Device configuration layout} > > + > > +Device configuration fields are listed below, they are read-only for a > > +driver. The \field{status} always exists. A single read-only bit (for > > +the driver) is currently defined for \field{status}: > > + > > +\begin{lstlisting} > > +struct virtio_can_config { > > +#define VIRTIO_CAN_S_CTRL_BUSOFF (1 << 0) > > + le16 status; > > +}; > > +\end{lstlisting} > > + > > +The bit VIRTIO_CAN_S_CTRL_BUSOFF in \field{status} is used to indicate > > +the unsolicited CAN controller state change from started to stopped due > > +to a detected bus off condition. > > + > > +\drivernormative{\subsubsection}{Device Initialization}{Device Types / CAN Device / Device Operation / Initialization} > > + > > +The driver MUST populate the \field{Rxq} with empty device-writeable > > +buffers of at least the size of struct virtio_can_rx, see section > > +\ref{struct virtio_can_rx}. > > + > > +\subsection{Device Operation}\label{sec:Device Types / CAN Device / Device Operation} > > + > > +A device operation has an outcome which is described by one of the > > +following values: > > + > > +\begin{lstlisting} > > +#define VIRTIO_CAN_RESULT_OK 0 > > +#define VIRTIO_CAN_RESULT_NOT_OK 1 > > +\end{lstlisting} > > + > > +Other values are to be treated like VIRTIO_CAN_RESULT_NOT_OK. > > + > > +\subsubsection{Controller Mode}\label{sec:Device Types / CAN Device / Device Operation / Controller Mode} > > + > > +The general format of a request in the \field{Controlq} is > > + > > +\begin{lstlisting} > > +struct virtio_can_control_out { > > +#define VIRTIO_CAN_SET_CTRL_MODE_START 0x0201 > > +#define VIRTIO_CAN_SET_CTRL_MODE_STOP 0x0202 > > + le16 msg_type; > > +}; > > +\end{lstlisting} > > + > > +To participate in bus communication the CAN controller is started by > > +sending a VIRTIO_CAN_SET_CTRL_MODE_START control message, to stop > > +participating in bus communication it is stopped by sending a > > +VIRTIO_CAN_SET_CTRL_MODE_STOP control message. Both requests are > > +confirmed by the result of the operation. > > + > > +\begin{lstlisting} > > +struct virtio_can_control_in { > > + u8 result; > > +}; > > +\end{lstlisting} > > + > > +If the transition succeeded the \field{result} is VIRTIO_CAN_RESULT_OK > > +otherwise it is VIRTIO_CAN_RESULT_NOT_OK. If a status update is > > +necessary, the device updates the configuration \field{status} before > > +marking the request used. As the configuration \field{status} change is > > +caused by a request from the driver the device is allowed to omit the > > +configuration change notification here. The device marks the request > > +used when the CAN controller has finalized the transition to the > > +requested controller mode. > > + > > +On transition to the STOPPED state the device cancels all CAN messages > > +already pending for transmission and marks them as used with > > +\field{result} VIRTIO_CAN_RESULT_NOT_OK. In the STOPPED state the > > +device marks messages received from the > > +\field{Txq} as used with \field{result} VIRTIO_CAN_RESULT_NOT_OK without > > +transmitting them to the CAN bus. > > + > > +Initially the CAN controller is in the STOPPED state. > > + > > +Control queue messages are processed in order. > > + > > +\devicenormative{\subsubsection}{CAN Message Transmission}{Device Types / CAN Device / Device Operation / CAN Message Transmission} > > + > > +The driver transmits messages by placing outgoing CAN messages in the > > +\field{Txq} virtqueue. > > + > > +\label{struct virtio_can_tx_out} > > +\begin{lstlisting} > > +struct virtio_can_tx_out { > > +#define VIRTIO_CAN_TX 0x0001 > > + le16 msg_type; > > + le16 length; /* 0..8 CC, 0..64 CAN-FD, 0..2048 CAN-XL, 12 bits */ > > + u8 reserved_classic_dlc; /* If CAN classic length = 8 then DLC can be 8..15 */ > > + u8 padding; > > + le16 reserved_xl_priority; /* May be needed for CAN XL priority */ > > +#define VIRTIO_CAN_FLAGS_FD 0x4000 > > +#define VIRTIO_CAN_FLAGS_EXTENDED 0x8000 > > +#define VIRTIO_CAN_FLAGS_RTR 0x2000 > > + le32 flags; > > + le32 can_id; > > + u8 sdu[]; > > +}; > > + > > +struct virtio_can_tx_in { > > + u8 result; > > +}; > > +\end{lstlisting} > > + > > +The length of the \field{sdu} is determined by the \field{length}. > > + > > +The type of a CAN message identifier is determined by \field{flags}. The > > +3 most significant bits of \field{can_id} do not bear the information > > +about the type of the CAN message identifier and are 0. > > + > > +The device MUST reject any CAN frame type for which support has not been > > +negotiated with VIRTIO_CAN_RESULT_NOT_OK in \field{result} and MUST NOT > > +schedule the message for transmission. A CAN frame with an undefined bit > > +set in \field{flags} is treated like a CAN frame for which support has > > +not been negotiated. > > + > > +The device MUST reject any CAN frame for which \field{can_id} or > > +\field{sdu} length are out of range or the CAN controller is in an > > +invalid state with VIRTIO_CAN_RESULT_NOT_OK in \field{result} and MUST > > +NOT schedule the message for transmission. > > + I am not very familiar with CAN but how does the device figure out that the can_id is out of range? Thanks, Matias.
