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

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 03/10/2015 11:25 PM, Rafael J. Wysocki wrote:
> 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?

So you want to have a native_backlight enum or some such ? with -1 being not_set ?

Regards,

Hans

>
>>
>>   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;
>>   }
>>
>>
>