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Subject: [PATCH v5] virtio-i2c: add the device specification
virtio-i2c is a virtual I2C adapter device. It provides a way to ïexibly communicate with the host I2C slave devices from the guest. This patch adds the specification for this device. Fixes: https://github.com/oasis-tcs/virtio-spec/issues/88 Signed-off-by: Jie Deng <jie.deng@intel.com> --- conformance.tex | 28 +++++++++-- content.tex | 1 + introduction.tex | 3 ++ virtio-i2c.tex | 139 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 167 insertions(+), 4 deletions(-) create mode 100644 virtio-i2c.tex diff --git a/conformance.tex b/conformance.tex index eb33240..e78adfd 100644 --- a/conformance.tex +++ b/conformance.tex @@ -27,8 +27,10 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} \ref{sec:Conformance / Driver Conformance / Socket Driver Conformance}, \ref{sec:Conformance / Driver Conformance / RPMB Driver Conformance}, \ref{sec:Conformance / Driver Conformance / IOMMU Driver Conformance}, -\ref{sec:Conformance / Driver Conformance / Sound Driver Conformance} or -\ref{sec:Conformance / Driver Conformance / Memory Driver Conformance}. +\ref{sec:Conformance / Driver Conformance / Sound Driver Conformance} +\ref{sec:Conformance / Driver Conformance / Memory Driver Conformance} or +\ref{sec:Conformance / Driver Conformance / I2C Adapter Driver Conformance}. + \item Clause \ref{sec:Conformance / Legacy Interface: Transitional Device and Transitional Driver Conformance}. \end{itemize} \item[Device] A device MUST conform to four conformance clauses: @@ -47,8 +49,10 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} \ref{sec:Conformance / Device Conformance / Socket Device Conformance}, \ref{sec:Conformance / Device Conformance / RPMB Device Conformance}, \ref{sec:Conformance / Device Conformance / IOMMU Device Conformance}, -\ref{sec:Conformance / Device Conformance / Sound Device Conformance} or -\ref{sec:Conformance / Device Conformance / Memory Device Conformance}. +\ref{sec:Conformance / Device Conformance / Sound Device Conformance} +\ref{sec:Conformance / Device Conformance / Memory Device Conformance} or +\ref{sec:Conformance / Device Conformance / I2C Adapter Device Conformance}. + \item Clause \ref{sec:Conformance / Legacy Interface: Transitional Device and Transitional Driver Conformance}. \end{itemize} \end{description} @@ -264,6 +268,14 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} \item \ref{drivernormative:Device Types / Memory Device / Device Operation / STATE request} \end{itemize} +\conformance{\subsection}{I2C Adapter Driver Conformance}\label{sec:Conformance / Driver Conformance / I2C Adapter Driver Conformance} + +An I2C Adapter driver MUST conform to the following normative statements: + +\begin{itemize} +\item \ref{drivernormative:Device Types / I2C Adapter Device / Device Operation} +\end{itemize} + \conformance{\section}{Device Conformance}\label{sec:Conformance / Device Conformance} A device MUST conform to the following normative statements: @@ -483,6 +495,14 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} \item \ref{devicenormative:Device Types / Memory Device / Device Operation / STATE request} \end{itemize} +\conformance{\subsection}{I2C Adapter Device Conformance}\label{sec:Conformance / Device Conformance / I2C Adapter Device Conformance} + +An I2C Adapter device MUST conform to the following normative statements: + +\begin{itemize} +\item \ref{devicenormative:Device Types / I2C Adapter Device / Device Operation} +\end{itemize} + \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 non-transitional, see \ref{intro:Legacy diff --git a/content.tex b/content.tex index 61eab41..48002a2 100644 --- a/content.tex +++ b/content.tex @@ -6484,6 +6484,7 @@ \subsubsection{Legacy Interface: Framing Requirements}\label{sec:Device \input{virtio-iommu.tex} \input{virtio-sound.tex} \input{virtio-mem.tex} +\input{virtio-i2c.tex} \chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits} diff --git a/introduction.tex b/introduction.tex index cc38e29..9f016d5 100644 --- a/introduction.tex +++ b/introduction.tex @@ -73,6 +73,9 @@ \section{Normative References}\label{sec:Normative References} \phantomsection\label{intro:HDA}\textbf{[HDA]} & High Definition Audio Specification, \newline\url{https://www.intel.com/content/dam/www/public/us/en/documents/product-specifications/high-definition-audio-specification.pdf}\\ + \phantomsection\label{intro:I2C}\textbf{[I2C]} & + I2C-bus specification and user manual, + \newline\url{https://www.nxp.com.cn/docs/en/user-guide/UM10204.pdf}\\ \end{longtable} diff --git a/virtio-i2c.tex b/virtio-i2c.tex new file mode 100644 index 0000000..fdb0050 --- /dev/null +++ b/virtio-i2c.tex @@ -0,0 +1,139 @@ +\section{I2C Adapter Device}\label{sec:Device Types / I2C Adapter Device} + +virtio-i2c is a virtual I2C adapter device. It provides a way to flexibly +organize and use the host I2C slave devices from the guest. By attaching +the host ACPI I2C slave nodes to the virtual I2C adapter device, the guest can +communicate with them without changing or adding extra drivers for these +slave I2C devices. + +\subsection{Device ID}\label{sec:Device Types / I2C Adapter Device / Device ID} +34 + +\subsection{Virtqueues}\label{sec:Device Types / I2C Adapter Device / Virtqueues} + +\begin{description} +\item[0] requestq +\end{description} + +\subsection{Feature bits}\label{sec:Device Types / I2C Adapter Device / Feature bits} + +None currently defined. + +\subsection{Device configuration layout}\label{sec:Device Types / I2C Adapter Device / Device configuration layout} + +None currently defined. + +\subsection{Device Initialization}\label{sec:Device Types / I2C Adapter Device / Device Initialization} + +\begin{enumerate} +\item The virtqueue is initialized. +\end{enumerate} + +\subsection{Device Operation}\label{sec:Device Types / I2C Adapter Device / Device Operation} + +\subsubsection{Device Operation: Request Queue}\label{sec:Device Types / I2C Adapter Device / Device Operation: Request Queue} + +The driver queues requests to the virtqueue, and they are used by the +device. The request is the representation of segments of an I2C +transaction. Each request is of form: + +\begin{lstlisting} +struct virtio_i2c_req { + le16 addr; + le32 flags; + le16 written; + le16 read; + u8 write_buf[]; + u8 read_buf[]; + u8 status; +}; +\end{lstlisting} + +The \field{addr} of the request is the address of the I2C slave device. + +The \field{flags} of the request is currently reserved as zero for future +feature extensibility. + +The \field{written} of the request is the number of data bytes in the \field{write_buf} +being written to the I2C slave address. + +The \field{read} of the request is the number of data bytes in the \field{read_buf} +being read from the I2C slave address. + +The \field{write_buf} of the request contains one segment of an I2C transaction +being written to the device. + +The \field{read_buf} of the request contains one segment of an I2C transaction +being read from the device. + +The final \field{status} byte of the request is written by the device: either +VIRTIO_I2C_MSG_OK for success or VIRTIO_I2C_MSG_ERR for error. + +\begin{lstlisting} +#define VIRTIO_I2C_MSG_OK 0 +#define VIRTIO_I2C_MSG_ERR 1 +\end{lstlisting} + +If the \field{read}=0 and the \field{written}>0, the request is called write request. + +If the \field{read}>0 and the \field{written}=0, the request is called read request. + +If the \field{read}>0 and the \field{written}>0, the request is called write-read request. +It means an I2C write segment followed by a read segment. Usually, the write segment +provides the number of an I2C slave device register to be read. + +The \field{read}=0 and at the same time the \field{written}=0 doesn't make any sense. +The driver SHOULD never send such request. + +\subsubsection{Device Operation: Operation Status}\label{sec:Device Types / I2C Adapter Device / Device Operation: Operation Status} + +A driver may send one request or multiple requests to the device at a time. +The requests in the virtqueue MUST be queued and processed in order. + +If a driver sends multiple requests at a time and a device fails to process +some of them, then the first failed request MUST have its \field{status} +being set to VIRTIO_I2C_MSG_ERR by the device and the requests after the first +failed one MUST also be treated as VIRTIO_I2C_MSG_ERR by the driver, +no matter what \field{status} of them. In this case, the number of successfully +sent requests this time is the number of the last request being successfully +processed. + +\drivernormative{\subsubsection}{Device Operation}{Device Types / I2C Adapter Device / Device Operation} + +A driver MUST set \field{addr}, \field{flags}(currently reserved as zero), +\field{written} and \field{read} before sending the request. + +A driver MUST place one segment of an I2C transaction into \field{write_buf} if the +\field{written}>0. + +A driver MUST NOT use \field{read_buf} if the final \field{status} returned +from the device is VIRTIO_I2C_MSG_ERR. + +A driver MAY queue one request or multiple requests at a time. + +A driver MUST queue the requests in order if multiple requests are going to +be sent at a time. + +If multiple requests are sent at a time and some of them returned from the +device have the \field{status} being VIRTIO_I2C_MSG_ERR, a driver MUST treat +the first failed request and the requests after the first failed one as +VIRTIO_I2C_MSG_ERR. + +\devicenormative{\subsubsection}{Device Operation}{Device Types / I2C Adapter Device / Device Operation} + +A device SHOULD keep consistent behaviors with the hardware as described in +\hyperref[intro:I2C]{I2C}. + +A device MUST NOT change the value of \field{addr}, \field{flags}, \field{written}, +\field{read} and \field{write_buf}. + +A device MUST place one segment of an I2C transaction into \field{read_buf} if the +\field{read}>0. + +A device MUST guarantee the requests in the virtqueue being processed in order +if multiple requests are received at a time. + +If multiple requests are received at a time and some of them being processed failed, +a device MUST set the \field{status} of the first failed request to be +VIRTIO_I2C_MSG_ERR and MAY set the \field{status} of the requests after +the first failed one to be VIRTIO_I2C_MSG_ERR. -- 2.7.4
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