On Sat, Apr 14, 2018 at 01:52:53PM +0200, Noralf Trønnes wrote:
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.
So my idea wasn't to rip the fbdev helper in half first (that's indeed a lot of work). But start out right away with using every piece of the drm_client infrastructure you're adding in the existing fbdev code.
That way there's not a huge patch series which just adds code, with no users, but every step of the way and every addition is tested almost right away. That makes more gradual merging also easier. The things I have in mind here is the generic fb_probe, or the drm_client block/unblock masters and all that stuff.
Then, once we've demonstrated all these auxiliary pieces necessary for drm_client.c work, we can cut the fb-helper in half and move the modeset code into the drm_client library.
I still prefer an even more gradual path like this compared to what you have in your patch series, but I understand that's yet another huge shuffle. And the current series seems like a good enough approach to get to essentially the same place.
Does the Intel CI test the fbdev emulation?
We have fbdev emulation enabled, and iirc there's even a few tests for fbdev. Just booting it on 20+ machines is a lot of testing itsefl already.
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.
Ugh, notifier is exactly what fbcon also uses. It just hides the locking horror show slightly, but it's equally bad. I'm working on a multi-year plan to rip out the fbcon notifier, please don't start another one. See
commit 6104c37094e729f3d4ce65797002112735d49cd1 Author: Daniel Vetter daniel.vetter@ffwll.ch Date: Tue Aug 1 17:32:07 2017 +0200
fbcon: Make fbcon a built-time depency for fbdev
for full details.
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
This is the same thing that defacto happens already with fbcon: You have to remove fbcon first (which holds a full ref on the fbdev, which prevents the drm driver from unloading). I think explicitly asking for that reference to disappear is ok.
It does mean everyone has to update their unload scripts, but oh well.
- Change drm_gem_prime_export() so it doesn't pin on client buffers
The double-loop in that patch definitely doesn't cut it, but worst case I think something like that could be made to work.
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.
Hm, missed that in my first cursory read of the series, I'l take another look. -Daniel
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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