Re: [git pull] habanalabs pull request for kernel 5.15

[Jeffrey Hugo]

On 8/19/2021 12:48 PM, Dave Airlie wrote:
> On Fri, 20 Aug 2021 at 03:07, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > On Thu, Aug 19, 2021 at 02:02:09PM +0300, Oded Gabbay wrote:
> > > Hi Greg,
> > >
> > > This is habanalabs pull request for the merge window of kernel 5.15.
> > > The commits divide roughly 50/50 between adding new features, such
> > > as peer-to-peer support with DMA-BUF or signaling from within a graph,
> > > and fixing various bugs, small improvements, etc.
> >
> > Pulled and pushed out, thanks!
>
> NAK for adding dma-buf or p2p support to this driver in the upstream
> kernel. There needs to be a hard line between
> "I-can't-believe-its-not-a-drm-driver" drivers which bypass our
> userspace requirements, and I consider this the line.
>
> This driver was merged into misc on the grounds it wasn't really a
> drm/gpu driver and so didn't have to accept our userspace rules.
>
> Adding dma-buf/p2p support to this driver is showing it really fits
> the gpu driver model and should be under the drivers/gpu rules since
> what are most GPUs except accelerators.

Care to elaborate?  I'm not trying to be cute, but all I see here is 
that dma-buf/p2p using drivers must be in drivers/gpu, yet many drivers 
outside of the gpu area use those features.  Surely your position can't 
be that only drivers/gpu can use dma-buf or p2p (which is part of the 
PCIe spec).

> We are opening a major can of worms (some would say merging habanalabs
> driver opened it), but this places us in the situation that if a GPU
> vendor just claims their hw is a "vector" accelerator they can use
> Greg to bypass all the work that been done to ensure we have
> maintainability long term. I don't want drivers in the tree using
> dma-buf to interact with other drivers when we don't have access to a
> userspace project to validate the kernel driver assumptions.

Umm, isn't that [1]?  The Habana device has the most open userspace I'm 
aware of.  Seems disingenuous to claim you don't have access to a 
userspace project for this driver.

[1] - https://github.com/HabanaAI/hl-thunk