Re: [PATCH] acpi: fix brightness level is initialized to zero when BIOS does not restore the brightness value to _BQC.

[joeyli <jlee@suse.com>]

於 一，2012-10-01 於 17:11 +0800，Alex Hung 提到：
> On 10/01/2012 04:34 PM, joeyli wrote:
> > 於 一，2012-10-01 於 15:17 +0800，joeyli 提到：
> >> 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@canonical.com>
> >>>>> ---
> >>>>>    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.
> >>
> >>
> >
> > Sorry for my misunderstood!
> >
> > I think that's possible the level_old is 0 and there have a 0 value in
> > the return package from _BCL.
> >
> 
> Yes, there is nothing wrong with _BCL and _BQC except that _BQC returns 
> a zero initially.
> 
> > Could you please share the _BCL in DSDT from issue machine? Does there
> > have 0 value in _BCL?
> 
> _BCL returns below data and there is a zero in the list.
> 
> [  744.572289] Brightness[0] = 100
> [  744.572293] Brightness[1] = 50
> [  744.572295] Brightness[2] = 0
> [  744.572297] Brightness[3] = 10
> [  744.572299] Brightness[4] = 20
> [  744.572301] Brightness[5] = 30
> [  744.572303] Brightness[6] = 40
> [  744.572305] Brightness[7] = 50
> [  744.572306] Brightness[8] = 60
> [  744.572308] Brightness[9] = 70
> [  744.572310] Brightness[10] = 80
> [  744.572312] Brightness[11] = 90
> [  744.572314] Brightness[12] = 100
> 
> The below is the complete _BCL for references
> 
>                  Method (_BCL, 0, Serialized)
>                  {
>                      Name (_T_0, Zero)
>                      If (_OSI ("NOT_WINP_KEY"))
>                      {
>                          While (One)
>                          {
>                              Store (LCDD, _T_0)
>                              If (LEqual (_T_0, 0x303CAF06))
>                              {
>                                  Return (AUOL)
>                              }
>                              Else
>                              {
>                                  If (LEqual (_T_0, 0x1475AE0D))
>                                  {
>                                      Return (CMIL)
>                                  }
>                                  Else
>                                  {
>                                      If (LEqual (_T_0, 0x033FE430))
>                                      {
>                                          Return (LGDL)
>                                      }
>                                      Else
>                                      {
>                                          If (LEqual (_T_0, 0x3942A34C))
>                                          {
>                                              Return (SAML)
>                                          }
>                                          Else
>                                          {
>                                              Return (DEFL)
>                                          }
>                                      }
>                                  }
>                              }
> 
>                              Break
>                          }
>                      }
>                      Else
>                      {
>                          Return (Package (0x0D)
>                          {
>                              0x64,
>                              0x32,
>                              Zero,

Yes, have Zero value in _BCL return package.

>                              0x0A,
>                              0x14,
>                              0x1E,
>                              0x28,
>                              0x32,
>                              0x3C,
>                              0x46,
>                              0x50,
>                              0x5A,
>                              0x64
>                          })
>                      }
>                  }
> 
> 

According to the above information, it make sense now!


Thank a lot!
Joey Lee

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