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

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

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.

Noralf.


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.
>
>
> 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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