On Sun, Oct 23, 2022 at 12:46:19AM +0300, Oded Gabbay wrote: > In the last couple of months we had a discussion [1] about creating a new > subsystem for compute accelerator devices in the kernel. > > After an analysis that was done by DRM maintainers and myself, and following > a BOF session at the Linux Plumbers conference a few weeks ago [2], we > decided to create a new subsystem that will use the DRM subsystem's code and > functionality. i.e. the accel core code will be part of the DRM subsystem. > > This will allow us to leverage the extensive DRM code-base and > collaborate with DRM developers that have experience with this type of > devices. In addition, new features that will be added for the accelerator > drivers can be of use to GPU drivers as well (e.g. RAS). > > As agreed in the BOF session, the accelerator devices will be exposed to > user-space with a new, dedicated device char files and a dedicated major > number (261), to clearly separate them from graphic cards and the graphic > user-space s/w stack. Furthermore, the drivers will be located in a separate > place in the kernel tree (drivers/accel/). > > This series of patches is the first step in this direction as it adds the > necessary infrastructure for accelerator devices to DRM. The new devices will > be exposed with the following convention: > > device char files - /dev/accel/accel* > sysfs - /sys/class/accel/accel*/ > debugfs - /sys/kernel/debug/accel/accel*/ > > I tried to reuse the existing DRM code as much as possible, while keeping it > readable and maintainable. > > One thing that is missing from this series is defining a namespace for the > new accel subsystem, while I'll add in the next iteration of this patch-set, > after I will receive feedback from the community. > > As for drivers, once this series will be accepted (after adding the namespace), > I will start working on migrating the habanalabs driver to the new accel > subsystem. I have talked about it with Dave and we agreed that it will be > a good start to simply move the driver as-is with minimal changes, and then > start working on the driver's individual features that will be either added > to the accel core code (with or without changes), or will be removed and > instead the driver will use existing DRM code. > > In addition, I know of at least 3 or 4 drivers that were submitted for review > and are good candidates to be included in this new subsystem, instead of being > a drm render node driver or a misc driver. > > [1] https://lkml.org/lkml/2022/7/31/83 > [2] https://airlied.blogspot.com/2022/09/accelerators-bof-outcomes-summary.html > Since this is new subsystem, it should have its own git tree where you collected accelerator-related patches. By convention, there should be "next" branch targeting for next kernel release and "fixes" branch for bugfixes pending for current release. Both branches should be included into linux-next. The names don't necessarily be that, though. Also, it had been great if you write short, descriptive documentation about the subsystem (maintainers handbook). Cc'ing linux-doc folks. -- An old man doll... just what I always wanted! - Clara
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