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

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Date:	Tue, 14 Jul 2009 02:53:26 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	ykzhao <yakui.zhao@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"rpurdie@...ys.net" <rpurdie@...ys.net>,
	"lenb@...nel.org" <lenb@...nel.org>,
	"Zhang, Rui" <rui.zhang@...el.com>,
	"corentincj@...aif.net" <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 08:58:48AM +0800, ykzhao wrote:

> It will be better to send the event to user space only when the
> brightness is updated successfully.

That guarantees that we have to read back the brightness, which may be 
expensive on some hardware.

> It seems that the acpi video driver will send the ACPI event to user
> space when updating the brightness. 
> Is it necessary to send the udev-event again?

Yes. There's no reason to special-case the ACPI driver.

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