linux-kernel - Re: [PATCH 2/2] drm: vblank: remove drm_timestamp

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Message-ID: <CAPj87rP9wG1H_5R2jR1R3cykRA7Vw7bpUFuj9AnDs39BU0Nz_Q@mail.gmail.com>
Date:   Wed, 11 Oct 2017 16:40:38 +0100
From:   Daniel Stone <daniel@...ishbar.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Sean Paul <seanpaul@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        Dave Airlie <airlied@...hat.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Alex Deucher <alexander.deucher@....com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] drm: vblank: remove drm_timestamp_monotonic parameter

On 11 October 2017 at 16:20, Arnd Bergmann <arnd@...db.de> wrote:
> There is a risk of overflowing vblank timestamps in 2038 or 2106 if
> someone sets the drm_timestamp_monotonic module parameter to zero.
>
> I found no indication of anyone ever setting the parameter, or
> complaining about the default being wrong, after it was introduced
> as a way to handle backwards-compatibility with linux prior to
> c61eef726a78 ("drm: add support for monotonic vblank timestamps"),
> so it's probably safer to just remove the parameter completely
> and only allowing the default behavior.

I don't think there's any reason to remain suspicious of
CLOCK_MONOTONIC in 2017. Not to mention that removing it wrecks
Weston/etc's ability to give clients present-timing feedback, so
removing it is a net uABI improvement.

Acked-by: Daniel Stone <daniels@...labora.com>

Cheers,
Daniel