Messages in this thread |  | | From | Keith Packard <> | Subject | Re: [PATCH 1/3] drm: Widen vblank count to 64 bits. Change vblank time precision to ns | Date | Thu, 06 Jul 2017 08:04:47 -0700 |
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Michel Dänzer <michel@daenzer.net> writes:
> Subtle breakage here: vblwait->request.sequence must still get updated > for _DRM_VBLANK_RELATIVE, in case we're interrupted by a signal.
Thanks for finding this.
I think it might be better to just not modify the request.type field instead, so that on re-entry it gets recomputed? That would mean that a signal might cause the value to be different if the application takes a long time processing the signal, but I'm not sure that's wrong?
>> @@ -317,6 +317,9 @@ int via_driver_irq_postinstall(struct drm_device *dev) >> if (!dev_priv) >> return -EINVAL; >> >> + if (dev->driver->get_vblank_counter) >> + dev->max_vblank_count = 0xffffffff; > > What's the purpose of this? All drivers providing get_vblank_counter > should already initialize max_vblank_count correctly.
Yeah, I couldn't prove that this driver did that, and as Daniel says, we haven't ever audited the drivers to make sure they do.
We have a check to see that they don't set max_vblank_count if they don't provide a get function, but I can't find the matching check for drivers that do provide a function and aren't setting max_vblank_count.
Do you have any thoughts on the wisdom of changing this API before we have a driver that needs it?
And, of course, thanks for your review!
-- -keith [unhandled content-type:application/pgp-signature] |  |