linux-kernel - Re: [Hdaps-devel] [PATCH] hdaps - switch to using input-polldev

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Date:	Tue, 10 Jul 2007 01:56:34 -0400
From:	"Shem Multinymous" <multinymous@...il.com>
To:	"Dmitry Torokhov" <dtor@...ightbb.com>
Cc:	hdaps-devel@...ts.sourceforge.net, rlove@...ve.org,
	"Linux Kernel ML" <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...l.org>,
	"Michael Riepe" <michael@...11.de>,
	"Henrique de Moraes Holschuh" <hmh@...ian.org>
Subject: Re: [Hdaps-devel] [PATCH] hdaps - switch to using input-polldev

On 7/9/07, Dmitry Torokhov <dtor@...ightbb.com> wrote:
> > Sounds good, then. It's a bit of a hack, but the benefits are well
> > worth it (if we can resolve the scheduling issue).
>
> You know, I slept on it and I think I want to move the polldev into
> opposite direction - to accomodte devices that need "relaxed" polling
> and are ok with polling being a bit irregular and maybe even rounded
> to next jiffy or something to better accomodate tickless kernels.

How about letting drivers and/or clients explicitly express their
scheduling needs, e.g., in terms of a desired polling rate and a
desired bound on scheduling irregularity? Given these requirements,
input-polldev will try to satisfy all requests (i.e., the harshest
one) made by the driver and current clients, on a "best effort" basis,
using minimal resources. (There should also be a way for a driver to
say "don't bother to poll more often than X or with regularity better
than Y even if a client asks for it -- the hardware isn't that fast
anyway".)

This way the same infrastructure could smoothly handle devices and
apps with vastly different polling needs.

That doesn't help much with the workqueue vs. timers issue, of course,
unless input-polldev implements *both*.

  Shem
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