On 03/18/2013 04:26 PM, Danny Baumann wrote:
> 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:
Yes, I see that, but I didn't really think about it until reviewing your
patch :-)
>
>>> - 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.
OK, thanks.
That would make people reading the code feel less confused, hopefully.
-Aaron
>
>>> + 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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