virtio-gpio is a virtual GPIO controller. It provides a way to flexibly communicate with the host GPIO controllers from the guest.
This patch adds the specification for it.
Based on the initial work done by: "Enrico Weigelt, metux IT consult" lkml@metux.net.
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/110 Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- V3 -> V4: - The GPIO line names must be unique within a device. - The gpio_names[0] field is dropped and gpio_names_offset field is added in place of the 2 bytes of padding. - New interrupts must not be initiated by the device, without a response for the previous one.
V2 -> V3: - Unused char in name string should be marked 0 now. - s/host/device/ and s/guest/driver/ - Added a new feature for IRQ mode, VIRTIO_GPIO_F_IRQ. - A new feature should be added for Version information if required later on.
V1 -> V2: - gpio_names_size is 32 bit. - gpio field is 16 bit. - padding added 16 bit. - Added packed attribute to few structures - Add the missing 'type' field to the request - Dropped to _nodata request/responses to simplify a bit, updated related text. --- conformance.tex | 26 +++- content.tex | 1 + virtio-gpio.tex | 309 ++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 332 insertions(+), 4 deletions(-) create mode 100644 virtio-gpio.tex
diff --git a/conformance.tex b/conformance.tex index a164cbb69093..5341abe096c2 100644 --- a/conformance.tex +++ b/conformance.tex @@ -29,8 +29,9 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} \ref{sec:Conformance / Driver Conformance / IOMMU Driver Conformance}, \ref{sec:Conformance / Driver Conformance / Sound Driver Conformance}, \ref{sec:Conformance / Driver Conformance / Memory Driver Conformance}, -\ref{sec:Conformance / Driver Conformance / I2C Adapter Driver Conformance} or -\ref{sec:Conformance / Driver Conformance / SCMI Driver Conformance}. +\ref{sec:Conformance / Driver Conformance / I2C Adapter Driver Conformance}, +\ref{sec:Conformance / Driver Conformance / SCMI Driver Conformance} or +\ref{sec:Conformance / Driver Conformance / GPIO Driver Conformance}.
\item Clause \ref{sec:Conformance / Legacy Interface: Transitional Device and Transitional Driver Conformance}. \end{itemize} @@ -52,8 +53,9 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} \ref{sec:Conformance / Device Conformance / IOMMU Device Conformance}, \ref{sec:Conformance / Device Conformance / Sound Device Conformance}, \ref{sec:Conformance / Device Conformance / Memory Device Conformance}, -\ref{sec:Conformance / Device Conformance / I2C Adapter Device Conformance} or -\ref{sec:Conformance / Device Conformance / SCMI Device Conformance}. +\ref{sec:Conformance / Device Conformance / I2C Adapter Device Conformance}, +\ref{sec:Conformance / Device Conformance / SCMI Device Conformance} or +\ref{sec:Conformance / Device Conformance / GPIO Device Conformance}.
\item Clause \ref{sec:Conformance / Legacy Interface: Transitional Device and Transitional Driver Conformance}. \end{itemize} @@ -288,6 +290,14 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} \item \ref{drivernormative:Device Types / SCMI Device / Device Operation / Setting Up eventq Buffers} \end{itemize}
+\conformance{\subsection}{GPIO Driver Conformance}\label{sec:Conformance / Driver Conformance / GPIO Driver Conformance} + +An GPIO driver MUST conform to the following normative statements: + +\begin{itemize} +\item \ref{drivernormative:Device Types / GPIO Device / Device Operation} +\end{itemize} + \conformance{\section}{Device Conformance}\label{sec:Conformance / Device Conformance}
A device MUST conform to the following normative statements: @@ -527,6 +537,14 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} \item \ref{devicenormative:Device Types / SCMI Device / Device Operation / Shared Memory Operation} \end{itemize}
+\conformance{\subsection}{GPIO Device Conformance}\label{sec:Conformance / Device Conformance / GPIO Device Conformance} + +An GPIO device MUST conform to the following normative statements: + +\begin{itemize} +\item \ref{devicenormative:Device Types / GPIO 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 d9913d056317..e572ac3bb6c0 100644 --- a/content.tex +++ b/content.tex @@ -6583,6 +6583,7 @@ \subsubsection{Legacy Interface: Framing Requirements}\label{sec:Device \input{virtio-mem.tex} \input{virtio-i2c.tex} \input{virtio-scmi.tex} +\input{virtio-gpio.tex}
\chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits}
diff --git a/virtio-gpio.tex b/virtio-gpio.tex new file mode 100644 index 000000000000..7582993f3fd9 --- /dev/null +++ b/virtio-gpio.tex @@ -0,0 +1,309 @@ +\section{GPIO Device}\label{sec:Device Types / GPIO Device} + +virtio-gpio is a virtual general purpose IO controller device. It provides a way +to access the host GPIO devices from the guest. This device provides a hardware +independent interface between the host and the guests. It allows the host to +club together GPIO lines from otherwise independent GPIO controllers and present +them as a single GPIO controller device at the guest. + +\subsection{Device ID}\label{sec:Device Types / GPIO Device / Device ID} +41 + +\subsection{Virtqueues}\label{sec:Device Types / GPIO Device / Virtqueues} + +\begin{description} +\item[0] command +\item[1] interrupt +\end{description} + +The \field{interrupt} virtqueue is only used if the \field{VIRTIO_GPIO_F_IRQ} +feature is supported by the device. + +\subsection{Feature bits}\label{sec:Device Types / GPIO Device / Feature bits} + +\begin{description} +\item[VIRTIO_GPIO_F_IRQ (0)] The device supports interrupts on GPIO lines. +\end{description} + + +\subsection{Device configuration layout}\label{sec:Device Types / GPIO Device / Device configuration layout} + +All fields of this configuration are always available and are read-only for the driver. + +\begin{lstlisting} +struct virtio_gpio_config { + char name[32]; + u16 ngpio; + u16 gpio_names_offset; + u32 gpio_names_size; +} __attribute__((packed)); +\end{lstlisting} + +\begin{description} +\item[\field{name}] is a null-terminated string that represents the name of the + GPIO controller. The unused characters in the string must be initialized to + zero by the device. + +\item[\field{ngpio}] is the total number of GPIO lines provided by the + controller. + +\item[\field{gpio_names_offset}] is the offset of the "gpio_names" memory block + from the base of the \field{struct virtio_gpio_config}. The "gpio names" + block contains a stream of \field{ngpio} null-terminated strings. Each and + every GPIO line name MUST be unique within a GPIO Device and the name MUST + not be NULL for any of the GPIO line, unless the \field{gpio_names_size} is + set to zero and this feature isn't used by the device. + + The \field{gpio_names_offset} field can only be used if the + \field{gpio_names_size} is set to a non-zero value. When used, its value + must be greater than or equal to the size of the \field{struct + virtio_gpio_config} (which is 40 bytes in the current version of the spec). + + This field is added, instead of fixing the offset of the "gpio_names" block + to the end of the structure, in order to allow the configuration structure + to be extended in future if need arises to add more fields to it. + +\item[\field{gpio_names_size}] is the size of the "gpio_names" memory block. + This field must be set to 0, if the "gpio_names" block is not used by the + device. +\end{description} + + +\subsection{Device Initialization}\label{sec:Device Types / GPIO Device / Device Initialization} + +\begin{enumerate} +\item The virtqueue is initialized. +\end{enumerate} + +\subsection{Device Operation}\label{sec:Device Types / GPIO Device / Device Operation} + +The operations of a virtio GPIO device are almost always driven by the driver. +The driver initiates one of the requests from \field{VIRTIO_GPIO_REQ_*} on the +\field{command} virtqueue and the device responds synchronously on the same +virtqueue with a response message. The only time a request is initiated by the +device is when it needs to report detection of an interrupt on a GPIO line and +the \field{VIRTIO_GPIO_F_IRQ} feature is supported by the device. This is done +by the device by sending the (\field{VIRTIO_GPIO_IRQ_EVENT}) request on the +\field{interrupt} virtqueue. + +\begin{lstlisting} +/* GPIO request types */ +#define VIRTIO_GPIO_REQ_ACTIVATE 0x01 +#define VIRTIO_GPIO_REQ_DEACTIVATE 0x02 +#define VIRTIO_GPIO_REQ_GET_DIRECTION 0x03 +#define VIRTIO_GPIO_REQ_DIRECTION_IN 0x04 +#define VIRTIO_GPIO_REQ_DIRECTION_OUT 0x05 +#define VIRTIO_GPIO_REQ_GET_VALUE 0x06 +#define VIRTIO_GPIO_REQ_SET_VALUE 0x07 +#define VIRTIO_GPIO_REQ_IRQ_TYPE 0x08 +#define VIRTIO_GPIO_REQ_IRQ_MASK 0x09 +#define VIRTIO_GPIO_REQ_IRQ_UNMASK 0x0a +#define VIRTIO_GPIO_IRQ_EVENT 0x0b +\end{lstlisting} + +\subsubsection{Device Operation: Request Queue}\label{sec:Device Types / GPIO Device / Device Operation: Request Queue} + +The communication between the device and the driver take place using a pair of +request and response messages. The virtio GPIO specification defines two request +and two response layouts. The particular request/response pair used for each +GPIO request type is specific later in the request specific sections. + +Supported request and response types: + +\begin{lstlisting} +/* Virtio GPIO Request */ +struct virtio_gpio_request { + u16 type; + u16 gpio; + u8 data; +} __attribute__((packed)); + +/* Virtio GPIO Response */ +struct virtio_gpio_response { + u8 status; + u8 data; +}; +\end{lstlisting} + +\begin{description} +\item[\field{type}] GPIO request type. +\item[\field{gpio}] GPIO line number. +\item[\field{data}] Request/Response specific data, not used by all + request/response messages. +\item[\field{status}] Status of the request, success or failure. +\end{description} + +Here is the list of different values these fields can contain based on the +specific request type. + +\begin{lstlisting} +/* GPIO line direction */ +#define VIRTIO_GPIO_DIRECTION_OUT 0x0 +#define VIRTIO_GPIO_DIRECTION_IN 0x1 + +/* GPIO line interrupt type */ +#define VIRTIO_GPIO_IRQ_TYPE_NONE 0x00 +#define VIRTIO_GPIO_IRQ_TYPE_EDGE_RISING 0x01 +#define VIRTIO_GPIO_IRQ_TYPE_EDGE_FALLING 0x02 +#define VIRTIO_GPIO_IRQ_TYPE_EDGE_BOTH 0x03 +#define VIRTIO_GPIO_IRQ_TYPE_LEVEL_HIGH 0x04 +#define VIRTIO_GPIO_IRQ_TYPE_LEVEL_LOW 0x08 + +/* Possible values of the status field */ +#define VIRTIO_GPIO_STATUS_OK 0x0 +#define VIRTIO_GPIO_STATUS_ERR 0x1 +\end{lstlisting} + +\subsubsection{Device Operation: Activate}\label{sec:Device Types / GPIO Device / Device Operation / Activate } + +The \field{VIRTIO_GPIO_REQ_ACTIVATE} request is initiated by the driver to +request the device to activate one of the GPIO lines for use. The driver sends +the \field{struct virtio_gpio_request} to the device, and the device responds +with \field{struct virtio_gpio_response}. Neither the request, nor the response +uses the \field{data} field. + +\subsubsection{Device Operation: Deactivate}\label{sec:Device Types / GPIO Device / Device Operation / Deactivate } + +The \field{VIRTIO_GPIO_REQ_DEACTIVATE} request is initiated by the driver to +request the device to deactivate one of the GPIO lines driver was previously +using. The driver sends the \field{struct virtio_gpio_request} to the device, +and the device responds with \field{struct virtio_gpio_response}. Neither the +request, nor the response uses the \field{data} field. + +\subsubsection{Device Operation: Get Direction}\label{sec:Device Types / GPIO Device / Device Operation / Get Direction } + +The \field{VIRTIO_GPIO_REQ_GET_DIRECTION} request is initiated by the driver to +request the device to return a GPIO line's configured direction. The driver +sends the \field{struct virtio_gpio_request} to the device, and the device +responds with \field{struct virtio_gpio_response}. The device shall set the +\field{data} field in the response to \field{VIRTIO_GPIO_DIRECTION_OUT} or +\field{VIRTIO_GPIO_DIRECTION_IN}. The request doesn't use the \field{data} +field. + +\subsubsection{Device Operation: Direction In}\label{sec:Device Types / GPIO Device / Device Operation / Direction In } + +The \field{VIRTIO_GPIO_REQ_DIRECTION_IN} request is initiated by the driver to +request the device to configure a GPIO line for input direction. The driver +sends the \field{struct virtio_gpio_request} to the device, and the device +responds with \field{struct virtio_gpio_response}. Neither the request, nor the +response uses the \field{data} field. + +\subsubsection{Device Operation: Direction Out}\label{sec:Device Types / GPIO Device / Device Operation / Direction Out } + +The \field{VIRTIO_GPIO_REQ_DIRECTION_OUT} request is initiated by the driver to +request the device to configure a GPIO line for output direction with an initial +output value (0 for low, 1 for high). The driver sends the \field{struct +virtio_gpio_request} to the device with initial output value set in the +\field{data} field, and the device responds with \field{struct +virtio_gpio_response}. The responds doesn't use the \field{data} field. + +\subsubsection{Device Operation: Get Value}\label{sec:Device Types / GPIO Device / Device Operation / Get Value } + +The \field{VIRTIO_GPIO_REQ_GET_VALUE} request is initiated by the driver to +request the device to return the current value sensed on a GPIO line (0 for low, +1 for high) configured for input. The driver sends the \field{struct +virtio_gpio_request} to the device, and the device responds responds with +\field{struct virtio_gpio_response} with its \field{data} field set to GPIO's +value. The request doesn't use the \field{data} field. + +\subsubsection{Device Operation: Set Value}\label{sec:Device Types / GPIO Device / Device Operation / Set Value } + +The \field{VIRTIO_GPIO_REQ_SET_VALUE} request is initiated by the driver to +request the device to set the value (0 for low, 1 for high) for a GPIO line +configured for output. The driver sends the \field{struct virtio_gpio_request} +to the device, with the output value set in the \field{data} field, and the +device responds with \field{struct virtio_gpio_response}. The responds doesn't +use the \field{data} field. + +\subsubsection{Device Operation: IRQ Type}\label{sec:Device Types / GPIO Device / Device Operation / IRQ Type } + +The \field{VIRTIO_GPIO_REQ_IRQ_TYPE} request is initiated by the driver to +request the device to set the IRQ trigger type (one of +\field{VIRTIO_GPIO_IRQ_TYPE_*}) for a GPIO line configured for input. The driver +sends the \field{struct virtio_gpio_request} to the device, with the IRQ trigger +type set in the \field{data} field, and the device responds with \field{struct +virtio_gpio_response}. The responds doesn't use the \field{data} field. + +This request is only supported if the \field{VIRTIO_GPIO_F_IRQ} feature is +supported by the device. + +\subsubsection{Device Operation: IRQ Mask}\label{sec:Device Types / GPIO Device / Device Operation / IRQ Mask } + +The \field{VIRTIO_GPIO_REQ_IRQ_MASK} request is initiated by the driver to +request the device to mask the specified GPIO line for interrupts. The driver +sends the \field{struct virtio_gpio_request} to the device, and the device +responds with \field{struct virtio_gpio_response}. Neither the request, nor the +response uses the \field{data} field. + +This request is only supported if the \field{VIRTIO_GPIO_F_IRQ} feature is +supported by the device. + +\subsubsection{Device Operation: IRQ Unmask}\label{sec:Device Types / GPIO Device / Device Operation / IRQ Unmask } + +The \field{VIRTIO_GPIO_REQ_IRQ_UNMASK} request is initiated by the driver to +request the device to unmask the specified GPIO line for interrupts. The driver +sends the \field{struct virtio_gpio_request} to the device, and the device +responds with \field{struct virtio_gpio_response}. Neither the request, nor the +response uses the \field{data} field. + +This request is only supported if the \field{VIRTIO_GPIO_F_IRQ} feature is +supported by the device. + +\subsubsection{Device Operation: IRQ Event}\label{sec:Device Types / GPIO Device / Device Operation / IRQ Event } + +The \field{VIRTIO_GPIO_IRQ_EVENT} request is the only request initiated by the +device to inform the driver that an interrupt is detected on one of the GPIO +lines configured for input. The device sends the \field{struct +virtio_gpio_request} to the driver, and the driver responds with \field{struct +virtio_gpio_response}. This is the only request that uses the \field{interrupt} +virtqueue, while all other requests use the \field{command} virtqueue. Neither +the request, nor the response uses the \field{data} field. The device shouldn't +initiate a new \field{VIRTIO_GPIO_IRQ_EVENT} request on the \field{interrupt} +virtqueue until the time it has received a response from the driver for the +previous \field{VIRTIO_GPIO_IRQ_EVENT} request. + +This request is only supported if the \field{VIRTIO_GPIO_F_IRQ} feature is +supported by the device. + + +\drivernormative{\subsubsection}{Device Operation}{Device Types / GPIO Device / Device Operation} + +A driver MUST set all the fields of the \field{struct virtio_gpio_request} +before sending the request, except for the requests where the \field{data} field +isn't used by the request type. + +A driver MUST NOT use the \field{data} field in the response message if the +\field{status} returned from the device is \field{VIRTIO_GPIO_STATUS_ERR}. + +A driver MUST NOT try to set value of a GPIO line configured for input. + +A driver MUST NOT try to get value of a GPIO line configured for output. + +A driver MUST NOT send IRQ related requests for a GPIO line configured for +output. + +A driver MUST NOT initiate IRQ related requests if the \field{VIRTIO_GPIO_F_IRQ} +feature is not supported by the device. + +A driver MUST queue only one request at a time and wait for its response before +queuing the next request. + +\devicenormative{\subsubsection}{Device Operation}{Device Types / GPIO Device / Device Operation} + +A device MUST set the \field{status} field to \field{VIRTIO_GPIO_STATUS_OK} for +all successful requests. + +A device MUST set all the fields of the \field{struct virtio_gpio_response} +before sending the response, except for the response where the \field{data} +field isn't used by the request type, unless an error has occurred and it has +set the \field{status} field to \field{VIRTIO_GPIO_STATUS_ERR}. + +A device MUST add a unique and valid string in the \field{gpio_names} field of +the \field{struct virtio_gpio_config} for every supported GPIO line, if the +\field{gpio_names_size} is set to a non-zero value. + +A device MUST NOT send a request on the \field{interrupt} virtqueue if the +\field{VIRTIO_GPIO_F_IRQ} feature is not supported by it. + +A device MUST NOT send a new request on the \field{interrupt} virtqueue if the +previous request is not responded to yet, by the driver.