linux-kernel - Re: [PATCH 00/15] Habana Labs kernel driver

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Message-ID: <CAOesGMh2CPrBn57b2H51+wVRtW0Y3SFpTOMGSSc4ombMkVLGNQ@mail.gmail.com>
Date:   Thu, 24 Jan 2019 16:13:58 -0800
From:   Olof Johansson <olof@...om.net>
To:     Dave Airlie <airlied@...il.com>
Cc:     Oded Gabbay <oded.gabbay@...il.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Jerome Glisse <jglisse@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>, ogabbay@...ana.ai,
        Arnd Bergmann <arnd@...db.de>, fbarrat@...ux.ibm.com,
        Andrew Donnellan <andrew.donnellan@....ibm.com>
Subject: Re: [PATCH 00/15] Habana Labs kernel driver

On Thu, Jan 24, 2019 at 2:23 AM Dave Airlie <airlied@...il.com> wrote:
>
> > I know I won't be able to convince you but I want to say that I think
> > your arguments for full userspace open source are not really
> > technical.
>
> There is more to keeping a kernel going than technical argument unfortunately.
>
> I guess the question for Greg, Olof etc, is do we care about Linux the
> kernel, or Linux the open source ecosystem, if the former, these sort
> of accelerator shim drivers are fine, useless to anyone who doesn't
> have all the magic hidden userspace, and impossible to support for
> anyone else, if the latter, we should leave the cost of maintenance to
> the company benefiting from it and leave maintaining it out of tree.

As mentioned in my reply to Daniel, I think we've got a history of
being pragmatic and finding reasonable trade-offs of what can be open
and what can be closed. For example, if truly care about open source
ecosystem, drivers that require closed firmware should also be
refused.

> Simple question like If I plug your accelerator into Power or ARM64,
> where do I get the port of your userspace to use it?

Does demanding complete open userspace get us closer to that goal in
reality? By refusing to work with people to enable their hardware,
they will still ship their platforms out of tree, using DKMS and all
the other ways of getting kernel modules installed to talk to the
hardware. And we'd be no closer.

In the end, they'd open up their userspace when there's business
reasons to do so. It's well-known how to work around refusal from us
to merge drivers by now, so it's not much leverage in that area.

> I'm not the final arbiter on this sort of thing, but I'm definitely
> going to make sure that anyone who lands this code is explicit in
> ignoring any experience we've had in this area and in the future will
> gladly accept "I told you so" :-)

There's only one final arbiter on any inclusion to code to the kernel,
but we tend to sort out most disagreements without going all the way
there.

I still think engaging has a better chance of success than rejecting
the contributions, especially with clear expectations w.r.t. continued
engagement and no second implementations over time. In all honestly,
either approach might fail miserably.

-Olof