linux-kernel - Re: [Linux-fbdev-devel] 2.6.21-rc2 radeon backlight

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Message-Id: <20070302135841.fbfc1e32.akpm@linux-foundation.org>
Date:	Fri, 2 Mar 2007 13:58:41 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	James Simmons <jsimmons@...radead.org>
Cc:	linux-fbdev-devel@...ts.sourceforge.net, rpurdie@...ys.net,
	romosan@...orax.lbl.gov, linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [Linux-fbdev-devel] 2.6.21-rc2 radeon backlight


(davem cc restored)

On Fri, 2 Mar 2007 21:41:12 +0000 (GMT)
James Simmons <jsimmons@...radead.org> wrote:

> > > > yes, if i disable the radeon backlight and use the ibm acpi module,
> > > > than the backlight works. if i enable the radeon backlight, the screen
> > > > stays dark and i can't turn it on (i tried using radeontool to control
> > > > it but nothing happened).
> > > 
> > > Richard, is this actually a bug, or is it a config error or something like that?
> > > 
> > > And should we track it as a post-2.6.20 regression?
> > 
> > Why don't we compromise for 2.6.21 by marking the Radeon backlight
> > stuff EXPERIMENTAL until the cases where IBM ACPI works and the
> > Radeon backlight stuff does not are worked out?
> 
> How about this?
> 
> diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
> index b8f0a11..eb54d1f 100644
> --- a/drivers/video/Kconfig
> +++ b/drivers/video/Kconfig
> @@ -679,7 +679,6 @@ config FB_NVIDIA
>  	depends on FB && PCI
>  	select I2C_ALGOBIT if FB_NVIDIA_I2C
>  	select I2C if FB_NVIDIA_I2C
> -	select FB_BACKLIGHT if FB_NVIDIA_BACKLIGHT
>  	select FB_MODE_HELPERS
>  	select FB_CFB_FILLRECT
>  	select FB_CFB_COPYAREA
> @@ -708,7 +707,8 @@ config FB_NVIDIA_I2C
>  
>  config FB_NVIDIA_BACKLIGHT
>  	bool "Support for backlight control"
> -	depends on FB_NVIDIA
> +	depends on FB_NVIDIA && EXPERIMENTAL
> +	select FB_BACKLIGHT
>  	default y
>  	help
>  	  Say Y here if you want to control the backlight of your display.
> @@ -717,7 +717,6 @@ config FB_RIVA
>  	tristate "nVidia Riva support"
>  	depends on FB && PCI
>  	select FB_DDC if FB_RIVA_I2C
> -	select FB_BACKLIGHT if FB_RIVA_BACKLIGHT
>  	select FB_MODE_HELPERS
>  	select FB_CFB_FILLRECT
>  	select FB_CFB_COPYAREA
> @@ -754,7 +753,8 @@ config FB_RIVA_DEBUG
>  
>  config FB_RIVA_BACKLIGHT
>  	bool "Support for backlight control"
> -	depends on FB_RIVA
> +	depends on FB_RIVA && EXPERIMENTAL
> +	select FB_BACKLIGHT
>  	default y
>  	help
>  	  Say Y here if you want to control the backlight of your display.
> @@ -994,7 +994,6 @@ config FB_RADEON
>  	tristate "ATI Radeon display support"
>  	depends on FB && PCI
>  	select FB_DDC if FB_RADEON_I2C
> -	select FB_BACKLIGHT if FB_RADEON_BACKLIGHT
>  	select FB_MODE_HELPERS
>  	select FB_CFB_FILLRECT
>  	select FB_CFB_COPYAREA
> @@ -1024,7 +1023,8 @@ config FB_RADEON_I2C
>  
>  config FB_RADEON_BACKLIGHT
>  	bool "Support for backlight control"
> -	depends on FB_RADEON
> +	depends on FB_RADEON && EXPERIMENTAL 
> +	select FB_BACKLIGHT
>  	default y
>  	help
>  	  Say Y here if you want to control the backlight of your display.
> @@ -1044,7 +1044,6 @@ config FB_ATY128
>  	select FB_CFB_FILLRECT
>  	select FB_CFB_COPYAREA
>  	select FB_CFB_IMAGEBLIT
> -	select FB_BACKLIGHT if FB_ATY128_BACKLIGHT
>  	select FB_MACMODES if PPC_PMAC
>  	help
>  	  This driver supports graphics boards with the ATI Rage128 chips.
> @@ -1056,7 +1055,8 @@ config FB_ATY128
>  
>  config FB_ATY128_BACKLIGHT
>  	bool "Support for backlight control"
> -	depends on FB_ATY128
> +	depends on FB_ATY128 && EXPERIMENTAL
> +	select FB_BACKLIGHT
>  	default y
>  	help
>  	  Say Y here if you want to control the backlight of your display.
> @@ -1067,7 +1067,6 @@ config FB_ATY
>  	select FB_CFB_FILLRECT
>  	select FB_CFB_COPYAREA
>  	select FB_CFB_IMAGEBLIT
> -	select FB_BACKLIGHT if FB_ATY_BACKLIGHT
>  	select FB_MACMODES if PPC
>  	help
>  	  This driver supports graphics boards with the ATI Mach64 chips.
> @@ -1106,7 +1105,8 @@ config FB_ATY_GX
>  
>  config FB_ATY_BACKLIGHT
>  	bool "Support for backlight control"
> -	depends on FB_ATY
> +	depends on FB_ATY && EXPERIMENTAL
> +	select FB_BACKLIGHT	
>  	default y
>  	help
>  	  Say Y here if you want to control the backlight of your display.

Sorry, but my confidence level on this one is very low.  We've had heaps
and heaps of Kconfig-related build errors in exactly this area.  I'd prefer
that a patch like this one have a lot of testing and review (and a
changelog?) before we let it near a tree.

coz I've been bitten before.

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