Nouveau - Feb 2025 - [RFC PATCH 0/3] gpu: nova-core: add basic timer subdevice implementation

On Thu Feb 27, 2025 at 1:42 PM PST, Dave Airlie wrote:
> On Thu, 27 Feb 2025 at 11:34, John Hubbard <jhubbard at nvidia.com>
wrote:
>> On Wed Feb 26, 2025 at 5:02 PM PST, Greg KH wrote:
>> > On Wed, Feb 26, 2025 at 07:47:30PM -0400, Jason Gunthorpe wrote:
...
> nova is just a drm driver, it's not a rewrite of the drm subsystem,
> that sort of effort would entail a much larger commitment.
Maybe at this point in the discussion it would help to discern between
nova-core and nova-drm:

    drivers/gpu/nova-core/ (under discussion here)
    drivers/gpu/drm/nova/ (Future)

...keeping in mind that nova-core will be used by other, non-DRM things,
notably VFIO.
>
> DRM has reasons for doing what drm does, that is a separate discussion
> of how a rust driver fits into the DRM. The rust code has to conform
> to the C expectations for the subsystems they are fitting into.
>
> The drm has spent years moving things to devm/drmm type constructs,
> adding hotplug with the unplug mechanisms, but it's a long journey and
> certainly not something nova would want to wait to reconstruct from
> scratch.
ack.

thanks,
John Hubbard

On Fri, 28 Feb 2025 at 09:07, John Hubbard <jhubbard at nvidia.com>
wrote:
>
> On Thu Feb 27, 2025 at 1:42 PM PST, Dave Airlie wrote:
> > On Thu, 27 Feb 2025 at 11:34, John Hubbard <jhubbard at
nvidia.com> wrote:
> >> On Wed Feb 26, 2025 at 5:02 PM PST, Greg KH wrote:
> >> > On Wed, Feb 26, 2025 at 07:47:30PM -0400, Jason Gunthorpe
wrote:
> ...
> > nova is just a drm driver, it's not a rewrite of the drm
subsystem,
> > that sort of effort would entail a much larger commitment.
>
> Maybe at this point in the discussion it would help to discern between
> nova-core and nova-drm:
>
>     drivers/gpu/nova-core/ (under discussion here)
nova-core won't be suffering any of the issues Jason is raising,
nova-core isn't going to have userspace facing interfaces or be part
of any subsystem with major lifetime expectations. It has to deal with
the hardware going away due to hot unplugs, and that is what this
devres is for.

nova-core will be a kernel internal pci driver, and vfio and nova-drm
will load on top of it, once those drivers are loaded and talking to
userspace they will keep references on the nova-core driver module
through normal means.

Dave.