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

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Message-ID: <20090714125507.GA21992@srcf.ucam.org>
Date:	Tue, 14 Jul 2009 13:55:07 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Richard Purdie <rpurdie@...ys.net>
Cc:	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	lenb@...nel.org, rui.zhang@...el.com, corentincj@...aif.net
Subject: Re: [PATCH 1/3] backlight: Allow drivers to update the core, and
	generate events on changes

On Tue, Jul 14, 2009 at 01:29:33PM +0100, Richard Purdie wrote:

> My main concern is that we don't start getting bug reports of 'missing'
> events and have clearly defined expectations of when we see what kind of
> events. For example, should an event be emitted when low battery causes
> the backlight to be limited? How about console blanking events turning
> off the backlight? Are there any other occasions we should be emitting
> change events and do we need to audit other drivers?

These are all good questions. I'm working through the drivers now, and 
there's definitely a few more that need doing.

> Also, are "userspace" and "kernel" as meaningful as they could be? Would
> "sysfs" and "hwkeys" make more sense and allow for other future hardware
> differences? Perhaps someone will tie the backlight to an ambient light
> sensor for example...

Yes, though we'd need to extend the interface slightly in that case to 
allow the information to be provided. The ALS case is a good one - if 
that ends up happening in-kernel then there probably shouldn't be a 
UI update.

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