-----Original Message-----
From: joeyli [mailto:jlee@xxxxxxxx]
Sent: Monday, October 01, 2012 5:19 PM
To: Alex Hung
Cc: Zhang, Rui; linux-acpi@xxxxxxxxxxxxxxx
Subject: Re: [PATCH] acpi: fix brightness level is initialized to zero
when BIOS does not restore the brightness value to _BQC.
Importance: High
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@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.
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
