linux-kernel - Re: [PATCH v6 3/4] drm: Expand max DRM device number to full MINORBITS

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Message-ID: <TAdBP5BOy3cy7VnUb4t7ZkDOMK6wI_gPCjXanItN3TOsA1TbSk_6yrlcPTqvk3AZjamo96yHlEhjpfNUPFF6tA_9K8iRoie3h_z5Jf6zNtc=@emersion.fr>
Date:   Fri, 28 Jul 2023 14:22:20 +0000
From:   Simon Ser <contact@...rsion.fr>
To:     Christian König <christian.koenig@....com>
Cc:     Michał Winiarski <michal.winiarski@...el.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        intel-gfx@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Matthew Wilcox <willy@...radead.org>,
        Oded Gabbay <ogabbay@...nel.org>,
        James Zhu <James.Zhu@....com>,
        Pekka Paalanen <pekka.paalanen@...labora.com>,
        Emil Velikov <emil.l.velikov@...il.com>
Subject: Re: [PATCH v6 3/4] drm: Expand max DRM device number to full MINORBITS

On Thursday, July 27th, 2023 at 14:01, Christian König <christian.koenig@....com> wrote:

> > We do need patches to stop trying to infer the node type from the minor
> > in libdrm, though. Emil has suggested using sysfs, which we already do
> > in a few places in libdrm.
> 
> That sounds like a really good idea to me as well.
> 
> But what do we do with DRM_MAX_MINOR? Change it or keep it and say apps
> should use drmGetDevices2() like Emil suggested?

DRM_MAX_MINOR has been bumped to 64 now.

With the new minor allocation scheme, DRM_MAX_MINOR is meaningless
because there is no "max minor per type" concept anymore: the minor no
longer contains the type.

So I'd suggest leaving it as-is (so that old apps still continue to
work on systems with < 64 devices like they do today) and mark it as
deprecated.