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<body><span class="vcard"><a class="email" href="mailto:frederic.plourde@collabora.co.uk" title="Frederic Plourde <frederic.plourde@collabora.co.uk>"> <span class="fn">Frederic Plourde</span></a>
</span> changed
<a class="bz_bug_link
bz_status_ASSIGNED "
title="ASSIGNED - Weston needs to detect when DRM pageflip timestamps are not supported"
href="https://bugs.freedesktop.org/show_bug.cgi?id=79502">bug 79502</a>
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<th>What</th>
<th>Removed</th>
<th>Added</th>
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<td style="text-align:right;">Status</td>
<td>NEW
</td>
<td>ASSIGNED
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<b><a class="bz_bug_link
bz_status_ASSIGNED "
title="ASSIGNED - Weston needs to detect when DRM pageflip timestamps are not supported"
href="https://bugs.freedesktop.org/show_bug.cgi?id=79502#c2">Comment # 2</a>
on <a class="bz_bug_link
bz_status_ASSIGNED "
title="ASSIGNED - Weston needs to detect when DRM pageflip timestamps are not supported"
href="https://bugs.freedesktop.org/show_bug.cgi?id=79502">bug 79502</a>
from <span class="vcard"><a class="email" href="mailto:frederic.plourde@collabora.co.uk" title="Frederic Plourde <frederic.plourde@collabora.co.uk>"> <span class="fn">Frederic Plourde</span></a>
</span></b>
<pre>This patch :
<a href="http://cgit.freedesktop.org/~fredinfinite23/weston/commit/?h=bad_timestamp_abort&id=507cfb65fba6ed2f4e0b3973f6335ba98aa97894">http://cgit.freedesktop.org/~fredinfinite23/weston/commit/?h=bad_timestamp_abort&id=507cfb65fba6ed2f4e0b3973f6335ba98aa97894</a>
is a fix for this,
but I'd like to discuss it some more, because I feel there is something
missing:
1) False-positive detection:
What if DRM driver 'sanely' returns a timestamp = 0 either by (mis)chance or
because of some weird DRM initial condition/behavior (first frame ?). We should
be given another chance to repaint.
2) Integer overflows:
What if we arrived at frame_time's max_range ? Next timestamp would then
break the 'cur > prev' rule and we would wrongly abort Weston.
I think those two considerations above call for some 'counter' on the
detection. Chances that we 'sanely' hit (stamp==0 || cur < prev) are really
low, but chances that we hit that twice in a row are practically 0. I don't see
any need for a customizable counter; I would set it to 1 by default and exit
Weston when it's 0.
opinions on that please :)</pre>
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