於 一，2012-10-01 於 15:03 +0800，Alex Hung 提到：
> On 10/01/2012 02:47 PM, joeyli wrote:
> > Hi Alex,
> >
> > 於 一，2012-10-01 於 13:39 +0800，Alex Hung 提到：
> >> Signed-off-by: Alex Hung <alex.hung@xxxxxxxxxxxxx>
> >> ---
> >> drivers/acpi/video.c | 4 ++++
> >> 1 files changed, 4 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
> >> index 42b226e..eaa9573 100644
> >> --- a/drivers/acpi/video.c
> >> +++ b/drivers/acpi/video.c
> >> @@ -724,6 +724,10 @@ acpi_video_init_brightness(struct acpi_video_device *device)
> >> if (level_old == br->levels[i])
> >> level = level_old;
> >> }
> >> +
> >> + if (level == 0)
> >> + level = br->levels[(br->count) / 2 + 1];
> >
> > Looks here used the 50% brightness level.
> >
> > Per comment in video.c, we want set the backlight to max_level when
> > level_old is invalid:
> >
> > 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
> > */
> >
> > I think here used max_level to fulfill it, e.g.
> >
> > + if (level == 0)
> > + level = max_level;
> >
> > How do you think?
> Hi Joey,
>
> I was debating with myself which level to be set, ex. 50%, ~75% or 100%,
> and I think 50% *might* be closer to normal use-case (just a personal
> guess).
>
> However, "max_level" seems to fit best if we treat the initial zero
> brightness in invalid. I can modify it according it that's preferred.
>
> Thanks for the feedback.
>
> Cheers,
> Alex Hung
>
hm.... I have a question for what's the BIOS's problem that causes
'level == 0'?
That implied the issue machine's max_level is 0?
/*
* Set the level to maximum and check if _BQC uses indexed value
*/
result = acpi_video_device_lcd_set_level(device, max_level); /* write max_level purposely, then read level back, compare them */
...
result = acpi_video_device_lcd_get_level_current(device, &level, 0);
...
br->flags._BQC_use_index = (level == max_level ? 0 : 1);
if (!br->flags._BQC_use_index) { /* _BQC_use_index is 0 will run into if, means level == max_level */
So, looks the 'level == max_level == 0' when level_old is invalid.
Just wonder what's defect of BIOS (in _BCL?) causes problem.
Thanks a lot!
Joey Lee
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