[RFC PATCH 00/17] VKMS: Add configfs support

[José Expósito]

Hi everyone,

This RFC implements support to configure VKMS using configfs.
It allows to:

 - Create multiple devices
 - Configure multiple overlay planes, CRTCs, encoders and
   connectors
 - Enable or disable cursor plane and writeback connector for
   each CRTC
 - Hot-plug/unplug connectors after device creation
 - Disable the creation of the default VKMS instance to be
   able to use only the configfs ones

This work is based on a previous attempt to implement configfs
support by Jim Shargo and Brandon Pollack [1].
I tried to keep the changes as minimal and simple as possible
and addressed Sima's comments on [1].

Currently, there is another RFC by Louis Chauvet [2]. As I
mentioned on his RFC, I'm not trying to push my implementation.
Instead, I think that having 2 implementations will make code
review way easier and I don't mind which implementation is used
as long as we get the feature implemented :)

I'm looking forward to analyzing Louis's implementation, seeing
what the differences are and finding a common solution.

What's missing?

 - DebugFS only works for the default VKMS instance.
   If we want to support it on instances created with configfs
   I'll need to implement it.

Known bugs:

 - When a CRTC is added and removed before device creation, there
   is a vblank warning.
   The issue is caused because vblanks are referenced using the
   CRTC index but, because one of the CRTCs is removed, the
   indices are not consecutives and drm_crtc_vblank_crtc() tries to
   access and invalid index
   I'm not sure if CRTC's indices *must* start at 0 and be
   consecutives or if this is a bug in the drm_crtc_vblank_crtc()
   implementation.

Best wishes,
José Expósito

[1] https://patchwork.kernel.org/project/dri-devel/list/?series=780110&archive=both
[2] https://lore.kernel.org/dri-devel/ZrZZFQW5RiG12ApN@louis-chauvet-laptop/T/#u

José Expósito (17):
  drm/vkms: Extract vkms_config header
  drm/vkms: Move default_config creation to its own function
  drm/vkms: Set device name from vkms_config
  drm/vkms: Allow to configure multiple CRTCs
  drm/vkms: Use managed memory to create encoders
  drm/vkms: Allow to configure multiple encoders
  drm/vkms: Use managed memory to create connectors
  drm/vkms: Allow to configure multiple connectors
  drm/vkms: Allow to configure multiple overlay planes
  drm/vkms: Allow to change connector status
  drm/vkms: Add and remove VKMS instances via configfs
  drm/vkms: Allow to configure multiple CRTCs via configfs
  drm/vkms: Allow to configure multiple encoders via configfs
  drm/vkms: Allow to configure multiple encoders
  drm/vkms: Allow to configure multiple planes via configfs
  drm/vkms: Allow to configure the default device creation
  drm/vkms: Remove completed task from the TODO list

 Documentation/gpu/vkms.rst            | 102 +++-
 drivers/gpu/drm/vkms/Kconfig          |   1 +
 drivers/gpu/drm/vkms/Makefile         |   4 +-
 drivers/gpu/drm/vkms/vkms_composer.c  |  30 +-
 drivers/gpu/drm/vkms/vkms_config.c    | 265 ++++++++++
 drivers/gpu/drm/vkms/vkms_config.h    | 101 ++++
 drivers/gpu/drm/vkms/vkms_configfs.c  | 721 ++++++++++++++++++++++++++
 drivers/gpu/drm/vkms/vkms_configfs.h  |   9 +
 drivers/gpu/drm/vkms/vkms_crtc.c      |  99 ++--
 drivers/gpu/drm/vkms/vkms_drv.c       |  75 ++-
 drivers/gpu/drm/vkms/vkms_drv.h       |  52 +-
 drivers/gpu/drm/vkms/vkms_output.c    | 187 ++++---
 drivers/gpu/drm/vkms/vkms_plane.c     |   6 +-
 drivers/gpu/drm/vkms/vkms_writeback.c |  27 +-
 14 files changed, 1464 insertions(+), 215 deletions(-)
 create mode 100644 drivers/gpu/drm/vkms/vkms_config.c
 create mode 100644 drivers/gpu/drm/vkms/vkms_config.h
 create mode 100644 drivers/gpu/drm/vkms/vkms_configfs.c
 create mode 100644 drivers/gpu/drm/vkms/vkms_configfs.h

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2.46.0