Re: [RFC PATCH 1/2] acpi: video: Allow forcing native backlight on non win8 machines

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Wednesday, March 04, 2015 10:50:20 AM Aaron Lu wrote:
> On 03/03/2015 09:11 PM, Hans de Goede wrote:
> > Hi,
> > 
> > On 03-03-15 09:26, Aaron Lu wrote:
> >> On 03/03/2015 03:39 PM, Hans de Goede wrote:
> >>> The native backlight behavior (so not registering both the acpi-video and the
> >>> vendor backlight driver) can be useful on some non win8 machines too, allow
> >>> the user to force this behavior by passing video.use_native_backlight=2
> >>> on the kernel commandline.
> >>
> >> Just bikeshedding, what about doing it this way?
> >>
> >> In the acpi_video_use_native_backlight function:
> >> 1 If user has set a cmdline option, use that(no matter if it is a win8
> >>    system or not);
> >> 2 If the system is in a DMI table, use that(no matter if it is a win8
> >>    system or not);
> >> 3 return true if this is a win8 system; false otherwise.
> >>
> >> Something like this:
> > 
> > That works for me, and has the added advantage of not changing the
> > cmdline syntax (but it does change the cmdline behavior ...).
> 
> Oh yes, I didn't consider this. Not sure how much impact this will have,
> but I don't see an immediate problem with it, so let's see.
> 
> > 
> > So going either way is fine with me.
> > 
> > Aaron's version is:
> > 
> > Acked-by: Hans de Goede <hdegoede@redhat.com>
> 
> Thanks. Here is the full patch:
> 
> From: Aaron Lu <aaron.lu@intel.com>
> Date: Wed, 4 Mar 2015 10:24:58 +0800
> Subject: [PATCH] acpi: video: Allow forcing native backlight on non win8
>  machines
> 
> The native backlight behavior (so not registering both the acpi-video
> and the vendor backlight driver) can be useful on some non win8 machines
> too, so change the behavior of the video.use_native_backlight=1 or 0
> kernel cmdline option to be: if user has set video.use_native_backlight=1
> or 0, use that no matter if it is a win8 system or not. Also, we will
> put some known systems into the DMI table to make them either use native
> backlight interface or not, so the use_native_backlight_dmi is used to
> reflect that.
> 
> Original-by: Hans de Goede <hdegoede@redhat.com>
> Signed-offby: Aaron Lu <aaron.lu@intel.com>
> Acked-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  drivers/acpi/video.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
> index debd30917010..4cd0c8a4fd9d 100644
> --- a/drivers/acpi/video.c
> +++ b/drivers/acpi/video.c
> @@ -84,7 +84,7 @@ module_param(allow_duplicates, bool, 0644);
>   */
>  static int use_native_backlight_param = -1;
>  module_param_named(use_native_backlight, use_native_backlight_param, int, 0444);
> -static bool use_native_backlight_dmi = true;
> +static int use_native_backlight_dmi = -1;

So can we have proper symbols instead of these numbers, please?

>  
>  static int register_count;
>  static struct mutex video_list_lock;
> @@ -239,13 +239,14 @@ static bool acpi_video_use_native_backlight(void)
>  {
>  	if (use_native_backlight_param != -1)
>  		return use_native_backlight_param;
> -	else
> +	else if (use_native_backlight_dmi != -1)
>  		return use_native_backlight_dmi;
> +	return acpi_osi_is_win8();
>  }
>  
>  bool acpi_video_verify_backlight_support(void)
>  {
> -	if (acpi_osi_is_win8() && acpi_video_use_native_backlight() &&
> +	if (acpi_video_use_native_backlight() &&
>  	    backlight_device_registered(BACKLIGHT_RAW))
>  		return false;
>  	return acpi_video_backlight_support();
> @@ -414,7 +415,7 @@ static int __init video_set_bqc_offset(const struct dmi_system_id *d)
>  
>  static int __init video_disable_native_backlight(const struct dmi_system_id *d)
>  {
> -	use_native_backlight_dmi = false;
> +	use_native_backlight_dmi = 0;
>  	return 0;
>  }
>  
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.