linux-kernel - Re: [PATCH 2.6.18-mm2] acpi: add backlight support to the sony

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Date:	Tue, 10 Oct 2006 11:10:13 -0500
From:	Matt Domsch <Matt_Domsch@...l.com>
To:	Richard Hughes <hughsient@...il.com>
Cc:	Yu Luming <luming.yu@...il.com>, Pavel Machek <pavel@....cz>,
	Andrew Morton <akpm@...l.org>,
	Alessandro Guido <alessandro.guido@...il.com>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	len.brown@...el.com, jengelh@...ux01.gwdg.de, gelma@...ma.net,
	ismail@...dus.org.tr
Subject: Re: [PATCH 2.6.18-mm2] acpi: add backlight support to the sony_acpi driver

On Tue, Oct 10, 2006 at 03:47:26PM +0100, Richard Hughes wrote:
> On Tue, 2006-10-10 at 22:32 +0800, Yu Luming wrote:
> > >From my understanding, a cute userspace App shouldn't have this kind
> > of logic:
> >         if (is  DELL )
> >                 invoke libsmbios
> >         if (is  foo)
> >                 invoke libfoo,
> >         if (is bar)
> >                 invoke libbar,
> >         ....
> >         else
> >                 operate on /sys/class/backlight/ ,.,..
> 
> This is what HAL has at the moment[1]. And it's hell to maintain, but
> works for a lot of users.

This is slightly different.  This shows that there are a number of
slightly different kernel implementations:

/proc/acpi/toshiba/lcd
/proc/acpi/asus/brn
/proc/acpi/pcc/brightness
/proc/acpi/ibm/brightness
/proc/acpi/sony/brightness
/proc/omnibook/lcd

which is indeed nasty. I'd agree all in-kernel solutions should use
the same kernel<->user interface.  I'd also expect the kernel to have
a generic ACPI driver that exports the _BCL and _BCM method
implementations via that same interface, so that systems providing
that will "just work".  drivers/acpi/video.c currently exports this
via /proc/acpi/video/$DEVICE/brightness, which isn't the same as
/sys/class/backlight. :-(

There's also at least one more userspace option for the sonypi using
spiictrl.  This is where I expected libsmbios to plug in also, as a
fallback to the ACPI _BCL/_BCM methods above.

Thanks,
Matt

-- 
Matt Domsch
Software Architect
Dell Linux Solutions linux.dell.com & www.dell.com/linux
Linux on Dell mailing lists @ http://lists.us.dell.com
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