I hit a 'Sending rate exceeded' error with this patchset, so it didn't go out as it should.
I will resend the patchset when I find out how to avoid this problem.


Den 12.04.2018 15.17, skrev Noralf Trønnes:
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.


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

- 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
   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: 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


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