drm/evdi: a Rust EVDI virtual display (a working KMS consumer)

evdi ("revdi" as a project) is a from-scratch Rust rewrite of DisplayLink's
out-of-tree evdi module: it presents virtual DRM/KMS displays whose scanout
is pulled by a userspace daemon over a drm_event + ioctl ABI, rather than
scanned out to local hardware. It identifies itself to userspace as "evdi"
for compatibility with the existing libevdi / DisplayLinkManager stack (an
ABI-compatible Rust rewrite of libevdi lives in the standalone project and
is not part of this posting).

Why post it as an RFC now: it is a *second, working* consumer of the safe
Rust KMS mode-object layer and the evdi/KMS bindings in the companion
series ("[RFC PATCH v2 00/18] rust: drm: safe KMS mode-object layer + evdi
bindings"). The other consumer posted alongside it, the vino DisplayLink
DL3 driver, is blocked at the dock's content-protection wall -- it never
gets the dock to engage its encrypted control plane, so it cannot prove
pixels actually flow on real hardware. evdi drives real monitors end to end
*today* under KWin/Wayland: multi-head output, live delta-damage updates,
a hardware cursor, DDC/CI, and clean teardown on unplug. So where vino
exercises this binding surface but can't demonstrate it, evdi does -- it is
the working validation of the same abstractions.

  1/2  drm/kms: three fixes to the safe Rust KMS layer, shaken out while
       bringing evdi up (a dangling mode_config vtable crash [RIP=0x9], a
       stale-cache coherency gap in the Framebuffer::vmap() guard, and a
       leaked-connector teardown). All are equally correct for vino and any
       other KmsDriver.
  2/2  the driver itself, under drivers/gpu/drm/evdi/.

NOT FOR MERGE AS POSTED: this depends on the not-yet-merged Rust DRM/KMS
bindings (the companion "rust: drm" series and the sync/DRM-registration
prerequisites it in turn depends on), so it does not build against mainline
as posted. It is sent to validate the binding surface with a driver that
works, and for review of the approach. Source:
  https://github.com/FireBurn/linux/tree/vino
  https://gitlab.freedesktop.org/FireBurn/linux/-/tree/vino

Mike Lothian (2):
  drm/kms: rust: fixes for a virtual KMS consumer
  drm/evdi: add the Rust EVDI virtual-display driver

 drivers/gpu/drm/Kconfig            |   2 +
 drivers/gpu/drm/Makefile           |   1 +
 drivers/gpu/drm/evdi/Kconfig       |  20 +
 drivers/gpu/drm/evdi/Makefile      |   2 +
 drivers/gpu/drm/evdi/ddcci.rs      |  43 +++
 drivers/gpu/drm/evdi/evdi.rs       | 405 ++++++++++++++++++++
 drivers/gpu/drm/evdi/ioctl.rs      | 248 ++++++++++++
 drivers/gpu/drm/evdi/kms.rs        | 589 +++++++++++++++++++++++++++++
 drivers/gpu/drm/evdi/painter.rs    | 199 ++++++++++
 drivers/gpu/drm/evdi/uapi.rs       | 210 ++++++++++
 rust/kernel/drm/driver.rs          |  24 +-
 rust/kernel/drm/kms.rs             |  12 +-
 rust/kernel/drm/kms/framebuffer.rs |  24 ++
 13 files changed, 1764 insertions(+), 15 deletions(-)
 create mode 100644 drivers/gpu/drm/evdi/Kconfig
 create mode 100644 drivers/gpu/drm/evdi/Makefile
 create mode 100644 drivers/gpu/drm/evdi/ddcci.rs
 create mode 100644 drivers/gpu/drm/evdi/evdi.rs
 create mode 100644 drivers/gpu/drm/evdi/ioctl.rs
 create mode 100644 drivers/gpu/drm/evdi/kms.rs
 create mode 100644 drivers/gpu/drm/evdi/painter.rs
 create mode 100644 drivers/gpu/drm/evdi/uapi.rs

-- 
2.55.0