linux-kernel - Re: [PATCH v2 1/2] drm/file: Rehabilitate the firstopen hook for non-legacy drivers

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Message-ID: <CAPj87rMJGUGFpYaBf=itf1A7jeEzOjPcnDDS-6m69kJN_mGnww@mail.gmail.com>
Date:   Fri, 29 Mar 2019 18:42:28 +0000
From:   Daniel Stone <daniel@...ishbar.org>
To:     Eric Anholt <eric@...olt.net>
Cc:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Eben Upton <eben@...pberrypi.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v2 1/2] drm/file: Rehabilitate the firstopen hook for
 non-legacy drivers

Hi,

On Fri, 29 Mar 2019 at 18:14, Eric Anholt <eric@...olt.net> wrote:
> Paul Kocialkowski <paul.kocialkowski@...tlin.com> writes:
> > I'm not totally convinced that it's okay to have a delay outside of
> > init/enumeration, even if it's a smaller delay.
>
> You'll have non-dumb buffers created during GL context creation, so
> early in xserver or other KMS-and-GL-using application init anyway.
> Seems like a perfectly fine plan to me.

Yeah. The alternative is doing it once when Plymouth starts, and then
maybe again when Weston/GNOME/Xorg/... starts, which isn't really
ideal (or maybe even udev helpers). Doing it on probe also complicates
profiling startup for those: if GL context or surface creation takes a
long time, that's easy to reason about. If opening an FD takes ages,
that makes figuring out why stuff is slow a lot more complicated. This
used to happen with RPM resume for PCI devices to read the device ID &
revision, which is why we now have an API that persists that to avoid
the delay.

Sorry this feedback is coming quite late into development.

Cheers,
Daniel