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

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Message-ID: <CAPM=9tyT_iouVE2v8J0SMJOLV=pr=QJOm88ud=bht4=5Ms2Y2A@mail.gmail.com>
Date:   Fri, 20 Aug 2021 04:48:18 +1000
From:   Dave Airlie <airlied@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Oded Gabbay <ogabbay@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [git pull] habanalabs pull request for kernel 5.15

On Fri, 20 Aug 2021 at 03:07, Greg KH <gregkh@...uxfoundation.org> 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.

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.

Dave.