xen: update PV-device interface headers

Update the Xen PV-device interface headers in order to avoid undefined
behavior with flexible arrays being defined with one array element.

Reported-by: Pry Mar <pryorm09@gmail.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/20231205115121.11627-1-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>

xen: fix wrong SPDX headers of Xen related headers

Commit b24413180f5600 ("License cleanup: add SPDX GPL-2.0 license
identifier to files with no license") was meant to do a tree-wide
cleanup for files without any license information by adding a SPDX
GPL-2.0 line to them.

Unfortunately this was applied even to several Xen-related headers
which have been originally under the MIT license, but obviously have
been copied to the Linux tree from the Xen project without keeping the
license boiler plate as required.

Correct that by changing the license of those files back to "MIT".

Some files still contain the MIT license text. Replace that by the
related SPDX line.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20211015143312.29900-1-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xen: Sync up with the canonical protocol definitions in Xen

This is the sync up with the canonical definitions of the input,
sound and display protocols in Xen.

Changes to kbdif:
1. Add missing string constants for {feature|request}-raw-pointer
to align with the rest of the interface file.

2. Add new XenStore feature fields, so it is possible to individually
control set of exposed virtual devices for each guest OS:
- set feature-disable-keyboard to 1 if no keyboard device needs
to be created
- set feature-disable-pointer to 1 if no pointer device needs
to be created

3. Move multi-touch device parameters to backend nodes: these are
described as a part of frontend's XenBus configuration nodes
while they belong to backend's configuration. Fix this by moving
the parameters to the proper section.

Unique-id field:
1. Add unique-id XenBus entry for virtual input and display.

2. Change type of unique-id field to string for sndif to align with
display and input protocols.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

xen/sndif: Sync up with the canonical definition in Xen

This is the sync up with the canonical definition of the sound
protocol in Xen:

1. Protocol version was referenced in the protocol description,
but missed its definition. Fixed by adding a constant
for current protocol version.

2. Some of the request descriptions have "reserved" fields
missed: fixed by adding corresponding entries.

3. Extend the size of the requests and responses to 64 octets.
Bump protocol version to 2.

4. Add explicit back and front synchronization
In order to provide explicit synchronization between backend and
frontend the following changes are introduced in the protocol:
- add new ring buffer for sending asynchronous events from
backend to frontend to report number of bytes played by the
frontend (XENSND_EVT_CUR_POS)
- introduce trigger events for playback control: start/stop/pause/resume
- add "req-" prefix to event-channel and ring-ref to unify naming
of the Xen event channels for requests and events

5. Add explicit back and front parameter negotiation
In order to provide explicit stream parameter negotiation between
backend and frontend the following changes are introduced in the protocol:
add XENSND_OP_HW_PARAM_QUERY request to read/update
configuration space for the parameters given: request passes
desired parameter's intervals/masks and the response to this request
returns allowed min/max intervals/masks to be used.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Oleksandr Grytsov <oleksandr_grytsov@epam.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xen/sndif: add sound-device ABI

Add ABI for the two halves of a para-virtualized
sound driver to communicate with each other.

The ABI allows implementing audio playback and capture as
well as volume control and possibility to mute/unmute
audio sources.

Note: depending on the use-case backend can expose more sound
cards and PCM devices/streams than the underlying HW physically
has by employing SW mixers, configuring virtual sound streams,
channels etc. Thus, allowing fine tunned configurations per
frontend.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Oleksandr Grytsov <oleksandr_grytsov@epam.com>
Signed-off-by: Oleksandr Dmytryshyn <oleksandr.dmytryshyn@globallogic.com>
Signed-off-by: Iurii Konovalenko <iurii.konovalenko@globallogic.com>
Acked-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>