[RFC v4 00/25] drm: Add generic fbdev emulation

["Noralf Trønnes" <noralf@tronnes.org>]

This patchset explores the possibility of having generic fbdev emulation
in DRM for drivers that supports dumb buffers which they can export. An
API is added to support in-kernel clients in general.

In this version I was able to reuse the modesetting code from
drm_fb_helper in the client API. This avoids code duplication, carries
over lessons learned and the modesetting code is bisectable. The
downside is that it takes +10 patches to rip drm_fb_helper in two, so
maybe it's not worth it wrt possible breakage and a challenging review.

Does the Intel CI test the fbdev emulation?

Daniel had this concern with the previous version:

    The register/unregister model needs more thought. Allowing both clients
    to register whenever they want to, and drm_device instances to come and
    go is what fbcon has done, and the resulting locking is a horror show.

    I think if we require that all in-kernel drm_clients are registers when
    loading drm.ko (and enabled/disabled only per module options and
    Kconfig), then we can throw out all the locking. That avoids a lot of
    the headaches.

I have solved this by adding a notifier that fires when a new DRM device
is registered (I've removed the new() callback). Currently only
bootsplash uses this. The fbdev client needs to be setup from the driver
since it can't know on device registration if the driver will setup it's
own fbdev emulation later and the vtcon client hooks up to a user
provided device id.

Since fbcon can't handle fb_open failing, the buffer has to be
pre-allocated. Exporting a GEM buffer pins the driver module making it
impossible to unload it.
I have included 2 solutions to the problem:
- sysfs file to remove/close clients: remove_internal_clients
- Change drm_gem_prime_export() so it doesn't pin on client buffers

If a dumb buffer is exported from a kernel thread (worker) context, the
file descriptor isn't closed and I leak a reference so the buffer isn't
freed. Please look at drm_client_buffer_create() in patch
'drm/client: Finish the in-kernel client API'.
This is a blocker that needs a solution.


Noralf.

Changes since version 3:
Client API changes:
- Drop drm_client_register_funcs() which attached clients indirectly.
  Let clients attach directly using drm_client_new{_from_id}(). Clients
  that wants to attach to all devices must be linked into drm.ko and use
  the DRM device notifier. This is done to avoid the lock/race
  register/unregister hell we have with fbcon. (Daniel Vetter)
- drm_client_display_restore() checks if there is a master and if so
  returns -EBUSY. (Daniel Vetter)
- Allocate drm_file up front instead of on-demand. Since fbdev can't do
  on demand buffer allocation because of fbcon, there's no need for this.
- Add sysfs file to remove clients
- Don't pin driver module when exporting gem client buffers
- Dropped page flip support since drm_fb_helper is now used for fbdev
  emulation.

- The bootsplash client now switches over to fbdev on keypress.

Changes since version 2:
- Don't set drm master for in-kernel clients. (Daniel Vetter)
- Add in-kernel client API

Changes since version 1:
- Don't add drm_fb_helper_fb_open() and drm_fb_helper_fb_release() to
  DRM_FB_HELPER_DEFAULT_OPS(). (Fi.CI.STATIC)
  The following uses that macro and sets fb_open/close: udlfb_ops,
  amdgpufb_ops, drm_fb_helper_generic_fbdev_ops, nouveau_fbcon_ops,
  nouveau_fbcon_sw_ops, radeonfb_ops.
  This results in: warning: Initializer entry defined twice
- Support CONFIG_DRM_KMS_HELPER=m (kbuild test robot)
  ERROR: <function> [drivers/gpu/drm/drm_kms_helper.ko] undefined!
- Drop buggy patch: (Chris Wilson)
  drm/prime: Clear drm_gem_object->dma_buf on release
- Defer buffer creation until fb_open.


David Herrmann (1):
  drm: provide management functions for drm_file

Noralf Trønnes (24):
  drm/file: Don't set master on in-kernel clients
  drm/fb-helper: No need to cache rotation and sw_rotations
  drm/fb-helper: Remove drm_fb_helper_debug_enter/leave()
  drm/fb-helper: dpms_legacy(): Only set on connectors in use
  drm/atomic: Move __drm_atomic_helper_disable_plane/set_config()
  drm: Begin an API for in-kernel clients
  drm/fb-helper: Use struct drm_client_display
  drm/fb-helper: Move modeset commit code to drm_client
  drm/connector: Add
    drm_connector_has_preferred_mode/pick_cmdline_mode()
  drm/connector: Add connector array functions
  drm/i915: Add drm_driver->initial_client_display callback
  drm/fb-helper: Remove struct drm_fb_helper_crtc
  drm/fb-helper: Remove struct drm_fb_helper_connector
  drm/fb-helper: Move modeset config code to drm_client
  drm: Make ioctls available for in-kernel clients
  drm/client: Bail out if there's a DRM master
  drm/client: Make the display modes available to clients
  drm/client: Finish the in-kernel client API
  drm/prime: Don't pin module on export for in-kernel clients
  drm/fb-helper: Add drm_fb_helper_fb_open/release()
  drm/fb-helper: Add generic fbdev emulation
  drm: Add DRM device registered notifier
  drm/client: Hack: Add bootsplash
  drm/client: Hack: Add DRM VT console client

 drivers/gpu/drm/Kconfig                 |    2 +
 drivers/gpu/drm/Makefile                |    4 +-
 drivers/gpu/drm/client/Kconfig          |   14 +
 drivers/gpu/drm/client/Makefile         |    3 +
 drivers/gpu/drm/client/drm_bootsplash.c |  248 ++++++
 drivers/gpu/drm/client/drm_vtcon.c      |  785 +++++++++++++++++
 drivers/gpu/drm/client/internal.h       |   19 +
 drivers/gpu/drm/drm_atomic.c            |  168 ++++
 drivers/gpu/drm/drm_atomic_helper.c     |  168 +---
 drivers/gpu/drm/drm_auth.c              |   33 +
 drivers/gpu/drm/drm_client.c            | 1448 +++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_connector.c         |  199 +++++
 drivers/gpu/drm/drm_crtc_internal.h     |   18 +-
 drivers/gpu/drm/drm_debugfs.c           |    7 +
 drivers/gpu/drm/drm_drv.c               |   43 +
 drivers/gpu/drm/drm_dumb_buffers.c      |   33 +-
 drivers/gpu/drm/drm_fb_helper.c         | 1420 ++++++++----------------------
 drivers/gpu/drm/drm_file.c              |  304 ++++---
 drivers/gpu/drm/drm_framebuffer.c       |   50 +-
 drivers/gpu/drm/drm_internal.h          |    7 +
 drivers/gpu/drm/drm_ioc32.c             |    2 +-
 drivers/gpu/drm/drm_ioctl.c             |    4 +-
 drivers/gpu/drm/drm_prime.c             |   37 +-
 drivers/gpu/drm/drm_probe_helper.c      |    3 +
 drivers/gpu/drm/drm_sysfs.c             |   20 +
 drivers/gpu/drm/i915/i915_drv.c         |    1 +
 drivers/gpu/drm/i915/intel_drv.h        |   11 +
 drivers/gpu/drm/i915/intel_fbdev.c      |  112 +--
 include/drm/drm_atomic.h                |    5 +
 include/drm/drm_atomic_helper.h         |    4 -
 include/drm/drm_client.h                |  182 ++++
 include/drm/drm_connector.h             |   11 +
 include/drm/drm_device.h                |    4 +
 include/drm/drm_drv.h                   |   25 +
 include/drm/drm_fb_helper.h             |  126 ++-
 35 files changed, 4007 insertions(+), 1513 deletions(-)
 create mode 100644 drivers/gpu/drm/client/Kconfig
 create mode 100644 drivers/gpu/drm/client/Makefile
 create mode 100644 drivers/gpu/drm/client/drm_bootsplash.c
 create mode 100644 drivers/gpu/drm/client/drm_vtcon.c
 create mode 100644 drivers/gpu/drm/client/internal.h
 create mode 100644 drivers/gpu/drm/drm_client.c
 create mode 100644 include/drm/drm_client.h

--
2.15.1

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