Re: [PATCH v2 3/3] ACPI video: Fix applying indexed initial brightnessvalue.

[Danny Baumann]

Hi,

>> +static unsigned long long
> > +acpi_video_bqc_value_to_level(struct acpi_video_device *device,
> > +			      unsigned long long bqc_value)
> > +{
> > +	unsigned long long level;
> > +
> > +	if (device->brightness->flags._BQC_use_index) {
> > +		if (device->brightness->flags._BCL_reversed)
> > +			bqc_value = device->brightness->count - 3 - bqc_value;
> > +
> > +		level = device->brightness->levels[bqc_value + 2];
>
> I don't understand this, what does the +2 have to do here?
> _BQC returned us an index, and then we should just convert it to level,
> why +2?
>
> The only explanation would be, for BIOS tables that return _BQC as
> index, they are indexing from the 3rd entry. Is it the case? If so, I
> think we need to put a comment here.

Yes, that's the case. The old code did the same thing:

> > -			if (device->brightness->flags._BQC_use_index) {
> > -				if (device->brightness->flags._BCL_reversed)
> > -					*level = device->brightness->count
> > -								 - 3 - (*level);
> > -				*level = device->brightness->levels[*level + 2];
> > +			*level = acpi_video_bqc_value_to_level(device, *level);

That's also the reason for the -3 instead of -1 in the BCL_reversed 
case. I can add a comment, though.

> > +	if (use_bios_initial_backlight) {
> > +		if (!br->flags._BQC_use_index) {
> > +			/*
> > +			 * Set the backlight to the initial state.
> > +			 * On some buggy laptops, _BQC returns an uninitialized
> > +			 * value when invoked for the first time, i.e.
> > +			 * level_old is invalid. Set the backlight to max_level
> > +			 * in this case.
> > +			 */
> >   			for (i = 2; i < br->count; i++)
> >   				if (level_old == br->levels[i]) {
> >   					level = level_old;
> >   					break;
> >   				}
> > +		} else {
> > +			level = acpi_video_bqc_value_to_level(device,
> > +							      level_old);
>
> What about we convert the value to level first?
>
> 	if (use_bios_initial_backlight) {
> 		level = acpi_video_bqc_value_to_level(device, level_old);
> 		/*
> 		 * Set the backlight to the initial state.
> 		 * On some buggy laptops, _BQC returns an uninitialized
> 		 * value when invoked for the first time, i.e.
> 		 * level_old is invalid(no matter it is a level, or an
> 		 * index.) Set the backlight to max_level in this case.
> 		 */
> 		for (i = 2; i < br->count; i++)
> 			if (level == br->levels[i])
> 				break;
> 		if (i == br->count)
> 			level = max_level;
> 	}

That works as well, and looks cleaner to me as well. I'll change that.

Regards,

Danny
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