linux-kernel - Re: [PATCH 1/3] backlight: Allow drivers to update the core, and generate events on changes

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Message-ID: <20090729152041.GA15650@srcf.ucam.org>
Date:	Wed, 29 Jul 2009 16:20:41 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Pavel Machek <pavel@....cz>
Cc:	Zhang Rui <rui.zhang@...el.com>,
	Richard Purdie <rpurdie@...ys.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"lenb@...nel.org" <lenb@...nel.org>,
	"corentincj@...aif.net" <corentincj@...aif.net>
Subject: Re: [PATCH 1/3] backlight: Allow drivers to update the core, and
	generate events on changes

On Wed, Jul 29, 2009 at 05:05:24PM +0200, Pavel Machek wrote:
> > No, I mean that the only default policy you could reasonably have in the 
> > kernel would be tying the backlight directly to the ALS. And that sucks. 
> > You need some degree of smoothing, and that's a job better left to 
> > userspace.
> 
> How would that be done? Wake up userspace 100times a second so it can
> read an integer and ardd it to running average?

I don't think you'd need more than once a second, possibly modified by 
the size of the change since the last measurement. Response doesn't need 
to be immediate.

> Is ALS device stupid sensor, or can it do some smoothing/watermarks
> itself?

Generally stupid.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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