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Subject: Re: [virtio-dev] Re: [PATCH v3] Add virtio input device specification.
On Tue, Oct 23, 2018 at 09:20:49AM -0400, Michael S. Tsirkin wrote: > On Tue, Oct 23, 2018 at 03:04:51PM +0200, Gerd Hoffmann wrote: > > Support has been added to the linux kernel version 4.1 > > and to qemu version 2.4. > > > > Signed-off-by: Ladi Prosek <lprosek@redhat.com> > > Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> > > Great, thank you! And given that it's been out without big changes for a long time, I'm inlined to say let's start voting on it. Do you agree? If yes pls create a github issue with link to archives, send the Fixes: tag and I'll get the ball rolling. Lots of conferences going on so I think we should do a longer than usual voting period, say 3 weeks. > > --- > > v2->v3: > > * add missing abs field to virtio_input_absinfo. > > > > v1->v2 (by Ladi): > > * added VIRTIO_INPUT_CFG_ID_DEVIDS / virtio_input_devids > > * added normative statements and moved them all to > > \devicenormative and \drivernormative sections > > * made it clearer that this specifies virtio transport, > > not evdev itself > > * Michael's feedback on the incremental patch > > * minor tweaks > > --- > > conformance.tex | 18 ++++++ > > content.tex | 2 + > > virtio-input.tex | 194 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 214 insertions(+) > > create mode 100644 virtio-input.tex > > > > diff --git a/conformance.tex b/conformance.tex > > index 7b7df32..2486e9a 100644 > > --- a/conformance.tex > > +++ b/conformance.tex > > @@ -145,6 +145,15 @@ An SCSI host driver MUST conform to the following normative statements: > > \item \ref{drivernormative:Device Types / SCSI Host Device / Device Operation / Device Operation: eventq} > > \end{itemize} > > > > +\subsection{Input Driver Conformance}\label{sec:Conformance / Driver Conformance / Input Driver Conformance} > > + > > +An input driver MUST conform to the following normative statements: > > + > > +\begin{itemize} > > +\item \ref{drivernormative:Device Types / Input Device / Device Initialization} > > +\item \ref{drivernormative:Device Types / Input Device / Device Operation} > > +\end{itemize} > > + > > \section{Device Conformance}\label{sec:Conformance / Device Conformance} > > > > A device MUST conform to the following normative statements: > > @@ -265,6 +274,15 @@ An SCSI host device MUST conform to the following normative statements: > > \item \ref{devicenormative:Device Types / SCSI Host Device / Device Operation / Device Operation: eventq} > > \end{itemize} > > > > +\subsection{Input Device Conformance}\label{sec:Conformance / Device Conformance / Input Device Conformance} > > + > > +An input device MUST conform to the following normative statements: > > + > > +\begin{itemize} > > +\item \ref{devicenormative:Device Types / Input Device / Device Initialization} > > +\item \ref{devicenormative:Device Types / Input Device / Device Operation} > > +\end{itemize} > > + > > \section{Legacy Interface: Transitional Device and > > Transitional Driver Conformance}\label{sec:Conformance / Legacy > > Interface: Transitional Device and > > diff --git a/content.tex b/content.tex > > index d989d98..4c0c4c9 100644 > > --- a/content.tex > > +++ b/content.tex > > @@ -5641,6 +5641,8 @@ descriptor for the \field{sense_len}, \field{residual}, > > \field{status_qualifier}, \field{status}, \field{response} and > > \field{sense} fields. > > > > +\input{virtio-input.tex} > > + > > \chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits} > > > > Currently there are three device-independent feature bits defined: > > diff --git a/virtio-input.tex b/virtio-input.tex > > new file mode 100644 > > index 0000000..044c714 > > --- /dev/null > > +++ b/virtio-input.tex > > @@ -0,0 +1,194 @@ > > +\section{Input Device}\label{sec:Device Types / Input Device} > > + > > +The virtio input device can be used to create virtual human interface > > +devices such as keyboards, mice and tablets. An instance of the virtio > > +device represents one such input device. Device behavior mirrors that > > +of the evdev layer in Linux, making pass-through implementations on top > > +of evdev easy. > > + > > +This specification defines how evdev events are transported > > +over virtio and how the set of supported events is discovered by a driver. > > +It does not, however, define the semantics of input events as this is > > +dependent on the particular evdev implementation. For the list of events > > +used by Linux input devices, see > > +\href{https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/input-event-codes.h}{include/uapi/linux/input-event-codes.h} > > +in the Linux source tree. > > + > > +\subsection{Device ID}\label{sec:Device Types / Input Device / Device ID} > > + > > +18 > > + > > +\subsection{Virtqueues}\label{sec:Device Types / Input Device / Virtqueues} > > + > > +\begin{description} > > +\item[0] eventq > > +\item[1] statusq > > +\end{description} > > + > > +\subsection{Feature bits}\label{sec:Device Types / Input Device / Feature bits} > > + > > +None. > > + > > +\subsection{Device configuration layout}\label{sec:Device Types / Input Device / Device configuration layout} > > + > > +Device configuration holds all information the guest needs to handle > > +the device, most importantly the events which are supported. > > + > > +\begin{lstlisting} > > +enum virtio_input_config_select { > > + VIRTIO_INPUT_CFG_UNSET = 0x00, > > + VIRTIO_INPUT_CFG_ID_NAME = 0x01, > > + VIRTIO_INPUT_CFG_ID_SERIAL = 0x02, > > + VIRTIO_INPUT_CFG_ID_DEVIDS = 0x03, > > + VIRTIO_INPUT_CFG_PROP_BITS = 0x10, > > + VIRTIO_INPUT_CFG_EV_BITS = 0x11, > > + VIRTIO_INPUT_CFG_ABS_INFO = 0x12, > > +}; > > + > > +struct virtio_input_absinfo { > > + le32 min; > > + le32 max; > > + le32 fuzz; > > + le32 flat; > > + le32 res; > > +}; > > + > > +struct virtio_input_devids { > > + le16 bustype; > > + le16 vendor; > > + le16 product; > > + le16 version; > > +}; > > + > > +struct virtio_input_config { > > + u8 select; > > + u8 subsel; > > + u8 size; > > + u8 reserved[5]; > > + union { > > + char string[128]; > > + u8 bitmap[128]; > > + struct virtio_input_absinfo abs; > > + struct virtio_input_devids ids; > > + } u; > > +}; > > +\end{lstlisting} > > + > > +To query a specific piece of information the driver sets > > +\field{select} and \field{subsel} accordingly, then checks \field{size} > > +to see how much information is available. \field{size} can be > > +zero if no information is available. Strings do not include a > > +NUL terminator. Related evdev ioctl names are provided for reference. > > +\begin{description} > > + > > +\item[VIRTIO_INPUT_CFG_ID_NAME] > > +\field{subsel} is zero. > > +Returns the name of the device, in \field{u.string}. > > + > > +Similar to EVIOCGNAME ioctl for Linux evdev devices. > > + > > +\item[VIRTIO_INPUT_CFG_ID_SERIAL] > > +\field{subsel} is zero. > > +Returns the serial number of the device, in \field{u.string}. > > + > > +\item[VIRTIO_INPUT_CFG_ID_DEVIDS] > > +\field{subsel} is zero. > > +Returns ID information of the device, in \field{u.ids}. > > + > > +Similar to EVIOCGID ioctl for Linux evdev devices. > > + > > +\item[VIRTIO_INPUT_CFG_PROP_BITS] > > +\field{subsel} is zero. > > +Returns input properties of the device, in \field{u.bitmap}. > > +Individual bits in the bitmap correspond to INPUT_PROP_* > > +constants used by the underlying evdev implementation. > > + > > +Similar to EVIOCGPROP ioctl for Linux evdev devices. > > + > > +\item[VIRTIO_INPUT_CFG_EV_BITS] > > +\field{subsel} specifies the event type using EV_* > > +constants in the underlying evdev implementation. If > > +\field{size} is non-zero the event type is supported and > > +a bitmap of supported event codes is returned in \field{u.bitmap}. > > +Individual bits in the bitmap correspond to > > +implementation-defined input event codes, for example keys > > +or pointing device axes. > > + > > +Similar to EVIOCGBIT ioctl for Linux evdev devices. > > + > > +\item[VIRTIO_INPUT_CFG_ABS_INFO] > > +\field{subsel} specifies the absolute axis using ABS_* > > +constants in the underlying evdev implementation. > > +Information about the axis will be returned in \field{u.abs}. > > + > > +Similar to EVIOCGABS ioctl for Linux evdev devices. > > + > > +\end{description} > > + > > +\subsection{Device Initialization}\label{sec:Device Types / Input Device / Device Initialization} > > + > > +\begin{enumerate} > > +\item The device is queried for supported event types and codes. > > +\item The eventq is populated with receive buffers. > > +\end{enumerate} > > + > > +\drivernormative{\subsubsection}{Device Initialization}{Device Types / Input Device / Device Initialization} > > +A driver MUST set both \field{select} and \field{subsel} when querying > > + device configuration, in any order. > > + > > +A driver MUST NOT write to configuration fields other than \field{select} > > + and \field{subsel}. > > + > > +A driver SHOULD check the \field{size} field before accessing the > > + configuration information. > > + > > +\devicenormative{\subsubsection}{Device Initialization}{Device Types / Input Device / Device Initialization} > > +A device MUST set the \field{size} field to zero if it doesn't support a > > + given \field{select} and \field{subsel} combination. > > + > > +\subsection{Device Operation}\label{sec:Device Types / Input Device / Device Operation} > > + > > +\begin{enumerate} > > +\item Input events such as press and release events for keys and > > + buttons, and motion events for pointing devices are sent from > > + the device to the driver using the eventq. > > +\item Status feedback such as keyboard LED updates are sent from the > > + driver to the device using the statusq. > > +\item Both queues use the same virtio_input_event struct. > > + \field{type}, \field{code} and \field{value} are filled according to > > + the Linux input layer (evdev) interface, except that the fields are > > + in little endian byte order whereas the evdev ioctl interface uses > > + native endian-ness. > > +\end{enumerate} > > + > > +\begin{lstlisting} > > +struct virtio_input_event { > > + le16 type; > > + le16 code; > > + le32 value; > > +}; > > +\end{lstlisting} > > + > > +\drivernormative{\subsubsection}{Device Operation}{Device Types / Input Device / Device Operation} > > + > > +A driver SHOULD keep the eventq populated with buffers. These buffers > > + MUST be device-writable and MUST be at least the size of > > + struct virtio_input_event. > > + > > +Buffers placed into the statusq by a driver MUST be at least the size > > + of struct virtio_input_event. > > + > > +A driver SHOULD ignore eventq input events it does not recognize. Note > > + that evdev devices generally maintain backward compatibility by sending > > + redundant events and relying on the consuming side using only the events > > + it understands and ignoring the rest. > > + > > +\devicenormative{\subsubsection}{Device Operation}{Device Types / Input Device / Device Operation} > > + > > +A device MAY drop input events if the eventq does not have enough > > + available buffers. It SHOULD NOT drop individual input events if > > + they are part of a sequence forming one input device update. For > > + example, a pointing device update typically consists of several > > + input events, one for each axis, and a terminating EV_SYN event. > > + A device SHOULD either buffer or drop the entire sequence. > > + > > -- > > 2.9.3 > > --------------------------------------------------------------------- > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org
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