linux-kernel - Re: [PATCH 1/3] drm: Widen vblank count to 64 bits. Change vblank time precision to ns

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Message-ID: <8760egutih.fsf@keithp.com>
Date:   Tue, 25 Jul 2017 13:54:46 -0700
From:   Keith Packard <keithp@...thp.com>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org,
        Dave Airlie <airlied@...hat.com>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 1/3] drm: Widen vblank count to 64 bits. Change vblank time precision to ns

Daniel Vetter <daniel@...ll.ch> writes:

> I'd drop that part (but keep 64 everywhere else ofc).

Yeah, we only ever ask drivers for a delta anyways, so keeping an
internal 64-bit value while retaining the 32-bit driver API is
easy to manage.

>> > Other thought on this, since you bother to change all the types: Afaik
>> > both timespec and timeval suffer from the 32bit issues.
>> 
>> I'm not sure what 32bit issues you're concerned about here? We don't
>> compare these values, just report them up to user space.
>
> Year 2038 32bit wrap-around bug. Yes I believe/fear drm will still be
> around then :-)

A fine point. I've switched to ktime_t, which has additional benefits in
making the internal interfaces a bit cleaner with pass-by-value possible
in more cases now.

I've pushed incremental patches out for all of the suggested changes to
my drm-sequence-64 branch. I think I'll send those out as incremental
patches and then also send out a squashed version from the original
branch point.

-- 
-keith

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