linux-kernel - Re: New subsystem for acceleration devices

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Message-ID: <CAPj87rMSNtqZUbH_5rmGAXpWONKhoZHJsjbw11PwYwXJi0b9jA@mail.gmail.com>
Date:   Thu, 4 Aug 2022 00:31:16 +0100
From:   Daniel Stone <daniel@...ishbar.org>
To:     Oded Gabbay <oded.gabbay@...il.com>
Cc:     Dave Airlie <airlied@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Yuji Ishikawa <yuji2.ishikawa@...hiba.co.jp>,
        Jiho Chu <jiho.chu@...sung.com>, Arnd Bergmann <arnd@...db.de>,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>
Subject: Re: New subsystem for acceleration devices

Hi Oded,

On Wed, 3 Aug 2022 at 21:21, Oded Gabbay <oded.gabbay@...il.com> wrote:
> The reason it happened now is because I saw two drivers, which are
> doing h/w acceleration for AI, trying to be accepted to the misc
> subsystem.

Why misc?

> Regarding the open source userspace rules in drm - yes, I think your
> rules are too limiting for the relatively young AI scene, and I saw at
> the 2021 kernel summit that other people from the kernel community
> think that as well.
> But that's not the main reason, or even a reason at all for doing
> this. After all, at least for habana, we open-sourced our compiler and
> a runtime library. And Greg also asked those two drivers if they have
> matching open-sourced user-space code.
>
> And a final reason is that I thought this can also help in somewhat
> reducing the workload on Greg. I saw in the last kernel summit there
> was a concern about bringing more people to be kernel maintainers so I
> thought this is a step in the right direction.

Can you please explain what the reason is here?

Everything you have described - uniform device enumeration, common job
description, memory management helpers, unique job submission format,
etc - applies exactly to DRM. If open userspace is not a requirement,
and bypassing Greg's manual merging is a requirement, then I don't see
what the difference is between DRM and this new bespoke subsystem. It
would be great to have these differences enumerated in email as well
as in kerneldoc.

Cheers,
Daniel