linux-kernel - Re: [PATCH] Input: evdev - use monotonic clock for event timestamps

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Message-ID: <20111007110542.GA5333@polaris.bitmath.org>
Date:	Fri, 7 Oct 2011 13:05:42 +0200
From:	"Henrik Rydberg" <rydberg@...omail.se>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Daniel Kurtz <djkurtz@...omium.org>,
	Chase Douglas <chasedouglas@...il.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: evdev - use monotonic clock for event timestamps

> > if the values don't change.  The timestamp axis
> > would always change, hence it would always be sent, even if no other
> > axes change.  Of course, we can mitigate this with special-case
> > handling of the ABS_TIMESTAMP in the evdev layer.
> > 
> 
> I'd prefer if we go this route then:
> 
> 1. Have input core emit this event. Then we could decide if we should
> suppress it when suppressing entire packet.

If we go this route, we could also make use of the time stamps of the
hardware, when existent.

> 2. Make it MSC_ event.
> 3. Turn it on and off via ioctl since not all users are interested in
> this facility.

Perhaps it is time for the per-file-descriptor event filters.

> OTOH if we do ioctl why don't we simply allow usres select monotnic vs
> wall time in event structure.
> 
> Still, why does your clock fluctuate so much that it matters?

Yes, some actual experimental timing data would be most interesting.

Thanks,
Henrik
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