linux-kernel - Re: [RFC PATCH v2 1/3] drivers/accel: define kconfig and register a new major

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Y2kRvyR8VrZrO/1H@nvidia.com>
Date:   Mon, 7 Nov 2022 10:10:07 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Oded Gabbay <ogabbay@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Arnd Bergmann <arnd@...db.de>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        John Hubbard <jhubbard@...dia.com>,
        Alex Deucher <alexander.deucher@....com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Yuji Ishikawa <yuji2.ishikawa@...hiba.co.jp>,
        Jiho Chu <jiho.chu@...sung.com>,
        Daniel Stone <daniel@...ishbar.org>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Jeffrey Hugo <quic_jhugo@...cinc.com>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jagan Teki <jagan@...rulasolutions.com>,
        Jacek Lawrynowicz <jacek.lawrynowicz@...ux.intel.com>,
        Maciej Kwapulinski <maciej.kwapulinski@...ux.intel.com>,
        stanislaw.gruszka@...el.com
Subject: Re: [RFC PATCH v2 1/3] drivers/accel: define kconfig and register a
 new major

On Mon, Nov 07, 2022 at 04:02:01PM +0200, Oded Gabbay wrote:
> On Mon, Nov 7, 2022 at 3:10 PM Jason Gunthorpe <jgg@...dia.com> wrote:
> >
> > On Mon, Nov 07, 2022 at 03:01:08PM +0200, Oded Gabbay wrote:
> > > I don't agree with your statement that it should be "a layer over top of DRM".
> > > Anything on top of DRM is a device driver.
> > > Accel is not a device driver, it is a new type of drm minor / drm driver.
> >
> > Yeah, I still think this is not the right way, you are getting almost
> > nothing from DRM and making everything more complicated in the
> > process.
> >
> > > The only alternative imo to that is to abandon the idea of reusing
> > > drm, and just make an independant accel core code.
> >
> > Not quite really, layer it properly and librarize parts of DRM into
> > things accel can re-use so they are not intimately tied to the DRM
> > struct device notion.
> >
> > IMHO this is much better, because accel has very little need of DRM to
> > manage a struct device/cdev in the first place.
> >
> > Jason
> I'm not following. How can an accel device be a new type of drm_minor,
> if it doesn't have access to all its functions and members ?

"drm_minor" is not necessary anymore. Strictly managing minor numbers
lost its value years ago when /dev/ was reorganized. Just use
dynamic minors fully.

> How will accel device leverage, for example, the GEM code without
> being a drm_minor ?

Split GEM into a library so it doesn't require that.

> Librarizing parts of DRM sounds nice in theory but the reality is that
> everything there is interconnected, all the structures are
> interdependent.

Yes, the kernel is full of stuff that needs improving. Let's not take
shortcuts.

> I would have to re-write the entire DRM library to make such a thing
> work. I don't think this was the intention.

Not necessarily you, whoever someday needs GEM would have to do some
work.

> The current design makes the accel device an integral part of drm,
> with very minimal code duplication and without re-writing DRM.

And it smells bad, you can't even make it into a proper module. Who
knows what other problems will come.

Jason