Bug 63111

 lspci is:
 00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) (prog-if 00 [VGA controller])
         Subsystem: Hewlett-Packard Company Device 1854
         Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
         Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
         Latency: 0
         Interrupt: pin A routed to IRQ 42
         Region 0: Memory at c2000000 (64-bit, non-prefetchable) [size=4M]
         Region 2: Memory at b0000000 (64-bit, prefetchable) [size=256M]
         Region 4: I/O ports at 4000 [size=64]
         Expansion ROM at <unassigned> [disabled]
         Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
                 Address: fee0f00c  Data: 41b1
         Capabilities: [d0] Power Management version 2
                 Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
                 Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
         Capabilities: [a4] PCI Advanced Features
                 AFCap: TP+ FLR+
                 AFCtrl: FLR-
                 AFStatus: TP-
         Kernel driver in use: i915

Created attachment 111181 [details]
dmesg

Thanks for reporting.

Possible to prepare a patch for this? You can reference driver/acpi/video.c, check video_dmi_table for callback video_ignore_initial_backlight, add your system there should be enough.

Created attachment 111471 [details]
patch

(In reply to Aaron Lu from comment #3)
>You can reference driver/acpi/video.c,

Intresting, there are many HP's laptops, as I see..

Thanks for the patch, please send it to linux ACPI mailing list for merge: linux-acpi@vger.kernel.org and cc ACPI maintainer "Rafael J. Wysocki" <rjw@rjwysocki.net>.

I've just done this

Patch sent to mailing list for merge:
https://patchwork.kernel.org/patch/3066081/

Please also attach acpidump here, I want to take a look, thanks.
# acpidump > acpidump.txt

Created attachment 112471 [details]
acpidump

The ASL code initialize initial brightness level to 100, but only for OS that is pre-vista. Don't know why it does this...

The _INI method is run during the ACPI device is first discovered.
Method (_INI, 0, NotSerialized)  // _INI: Initialize
{
	If (LLess (OSYS, 0x07D6))
	{
		Store (0x64, BRTL)
	}
	... ...
}

The _BQC method is used to tell the current brightness level
Method (_BQC, 0, NotSerialized)  // _BQC: Brightness Query Current
{
	Return (BRTL)
}

Since it is not initialized in _INI(as we report to firmware we are Windows 2012), the video module thought the initial brightness level is 0 and then set level 0. The cmdline option use_bios_initial_backlight=0 is used to tell video module that the initial backlight level firmware reported is wrong and do not use it.

I'm very far from ACPI logic, so your answer on this binary acpidump really sounds like a magic for me ;)

Thanks for your Reviewed-by.

(In reply to Aaron Lu from comment #11)
> The ASL code initialize initial brightness level to 100, but only for OS
> that is pre-vista. Don't know why it does this...

May be in case of this notebook vista prints something ugly on the screen during short period of initial initialization (just "to finding a mare's nest" -- if google translator does not lie about this idiom :)

commit e37f14a5fb85522f3bbf88ece6134c4e610ed598
Author: Kirill Tkhai <tkhai@yandex.ru>
Date:   Fri Oct 18 15:56:44 2013 +0400

    ACPI / video: Ignore BIOS initial backlight value for HP 250 G1

Entered maintainer's linux-next branch.

It turned out there are more systems share this problem:
https://bugzilla.kernel.org/show_bug.cgi?id=61231
https://bugzilla.kernel.org/show_bug.cgi?id=64031

To avoid adding too many systems to the quirk table, I made a patch to fix the initial brightness level 0 problem, see here:
https://bugzilla.kernel.org/show_bug.cgi?id=61231#c10

Can you please test it too? If it can also solve your problem, we can save an entry in DMI table, thanks.

Yes, the patches solve the problem.

commit 2c62333a408f5badd2d2ffd7177f95deeccc5ca4
Author: Aaron Lu <aaron.lu@intel.com>
Date:   Wed Nov 6 09:07:10 2013 +0800

    ACPI / video: Quirk initial backlight level 0

Entered Linus' tree.