This is the third version of the RFC following the comments given on the second version, but more importantly, following testing done by the VPU driver people and myself. We found out that there is a circular dependency between DRM and accel. DRM calls accel exported symbols during init and when accel devices are registering (all the minor handling), then accel calls DRM exported symbols. Therefore, if the two components are compiled as modules, there is a circular dependency. To overcome this, I have decided to compile the accel core code as part of the DRM kernel module (drm.ko). IMO, this is inline with the spirit of the design choice to have accel reuse the DRM core code and avoid code duplication. Another important change is that I have reverted back to use IDR for minor handling instead of xarray. This is because I have found that xarray doesn't handle well the scenario where you allocate a NULL entry and then exchange it with a real pointer. It appears xarray still considers that entry a "zero" entry. This is unfortunate because DRM works that way (first allocates a NULL entry and then replaces the entry with a real pointer). I decided to revert to IDR because I don't want to hold up these patches, as many people are blocked until the support for accel is merged. The xarray issue should be fixed as a separate patch by either fixing the xarray code or changing how DRM + ACCEL do minor id handling. The patches are in the following repo: https://git.kernel.org/pub/scm/linux/kernel/git/ogabbay/accel.git/log/?h=accel_v3 As in v2, The HEAD of that branch is a commit adding a dummy driver that registers an accel device using the new framework. This can be served as a simple reference. I have checked inserting and removing the dummy driver, and opening and closing /dev/accel/accel0 and nothing got broken :) v1 cover letter: https://lkml.org/lkml/2022/10/22/544 v2 cover letter: https://lore.kernel.org/lkml/20221102203405.1797491-1-ogabbay@xxxxxxxxxx/T/ Thanks, Oded. Oded Gabbay (3): drivers/accel: define kconfig and register a new major accel: add dedicated minor for accelerator devices drm: initialize accel framework Documentation/admin-guide/devices.txt | 5 + MAINTAINERS | 8 + drivers/Kconfig | 2 + drivers/accel/Kconfig | 24 ++ drivers/accel/drm_accel.c | 322 ++++++++++++++++++++++++++ drivers/gpu/drm/Makefile | 1 + drivers/gpu/drm/drm_drv.c | 102 +++++--- drivers/gpu/drm/drm_file.c | 2 +- drivers/gpu/drm/drm_sysfs.c | 24 +- include/drm/drm_accel.h | 97 ++++++++ include/drm/drm_device.h | 3 + include/drm/drm_drv.h | 8 + include/drm/drm_file.h | 21 +- 13 files changed, 582 insertions(+), 37 deletions(-) create mode 100644 drivers/accel/Kconfig create mode 100644 drivers/accel/drm_accel.c create mode 100644 include/drm/drm_accel.h -- 2.25.1
