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    SubjectRe: [PATCH] Added backlight driver for Acer Aspire 4736
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    於 日,2012-03-18 於 10:40 +0530,Pradeep Subrahmanion 提到:
    > On Thu, 2012-03-15 at 16:05 +0800, joeyli wrote:
    > > Hi Pradeep,
    > >
    > > 於 三,2012-03-14 於 11:47 +0530,Pradeep Subrahmanion 提到:
    > > > On Wed, Mar 14, 2012 at 11:21 AM, joeyli <jlee@suse.com> wrote:
    > > > > 於 三,2012-03-14 於 08:13 +0530,Pradeep Subrahmanion 提到:
    > > > >> Hi Joey ,
    > > > >>
    > > > >> > Per my understood, EC firmware should change brightness but didn't do
    > > > >> > that, another
    > > > >> > way is touch i915 register in _BCM.
    > > > >>
    > > > >> how do we do this ? you mean change the _BCM implementation ?
    > > > >
    > > > > "BIOS guy" should do something like this:
    > > > >
    > > > > Method (AINT, 2, NotSerialized)
    > > > > {
    > > > > ...
    > > > > If (LEqual (Arg0, One))
    > > > > {
    > > > > Store (Divide (Multiply (Arg1, 0xFF), 0x64, ), BCLP)
    > > > > Or (BCLP, 0x80000000, BCLP) <=== touch BCLP register
    > > > > Store (0x02, ASLC)
    > > > > }
    > > > >
    > > > > Method (_BCM, 1, NotSerialized)
    > > > > {
    > > > > If (LAnd (LGreaterEqual (Arg0, Zero), LLessEqual (Arg0, 0x64)))
    > > > > {
    > > > > AINT (One, Arg0) <=== call AINT method
    > > > > Store (Arg0, BRTL)
    > > > > }
    > > > > }
    > > > >
    > > > >
    > > > > Just for reference, they should do that when EC didn't wire to
    > > > > backlight.
    > > > >
    > > > >> >
    > > > >> > Acer machine provide a broken _BCM implementation and they didn't test
    > > > >> > it.
    > > > >> >
    > > > >> > > > > By ' ACPI interface' , I mean 'acpi_video0' inside the
    > > > >> > > > > /sys/class/backlight. I havn't tried the /sys/class/backlight interface
    > > > >> > > > > directly . I will try that also.
    > > > >> > > >
    > > > >> > > > So writing values into /sys/class/backlight/acpi_video0/brightness does
    > > > >> > > > nothing?
    > > > >> > >
    > > > >> > >
    > > > >> > > No change in value when writing
    > > > >> > > to /sys/class/backlight/acpi_video0/brightness.
    > > > >> > >
    > > > >> > > Another thing is that when i did boot with acpi_backlight = 'acer_wmi' ,
    > > > >> > > in new kernel (3.3.0-rc7) , it shows following messages ,
    > > > >> > >
    > > > >> > > [ 8.350825] wmi: Mapper loaded
    > > > >> > > [ 10.363975] acer_wmi: Acer Laptop ACPI-WMI Extras
    > > > >> > > [ 10.396186] acer_wmi: Function bitmap for Communication Device: 0x91
    > > > >> > > [ 10.396385] acer_wmi: Brightness must be controlled by generic video
    > > > >> > > driver
    > > > >> > >
    > > > >> > > Also there was no interface inside /sys/class/backlight for acer_wmi.
    > > > >> > >
    > > > >> >
    > > > >> > Yes, acer_wmi support backlight control with AMW0 interface, your
    > > > >> > machine didn't have AMW0 interface.
    > > > >> >
    > > > >> > Normally, backlight should control by standard acpi interface.
    > > > >> >
    > > > >> > > I also tried writing directly to Embedded controller register .But no
    > > > >> > > change.
    > > > >> >
    > > > >> > The machine has broken _BCM method, because EC should do something after
    > > > >> > _BCM changed EC register.
    > > > >>
    > > > >> Thanks ,
    > > > >>
    > > > >> Pradeep Subrahmanion
    > > > >
    > > > > Why they didn't find _BCM not work?
    > > > >
    > > > > My guess is:
    > > > >
    > > > > Because the backlight control is through WDDM driver on Windows platform
    > > > > but not through standard ACPI method _BCM. They only test Windows
    > > > > platform, so, they didn't find _BCM broken.
    > > > >
    > > > > And, they also didn't really follow Microsoft WDDM spec:
    > > > >
    > > > > http://msdn.microsoft.com/en-us/windows/hardware/gg487382.aspx
    > > > >
    > > > > Per spec,
    > > > > ODM should keep _BCM works fine for any other OS didn't support WDDM
    > > > > driver, but they didn't.
    > > > >
    > > > > At last year, I told Acer PM one time for this issue, they said will
    > > > > check but finally didn't response me.
    > > > >
    > > >
    > > > >
    > > > > Thanks
    > > > > Joey Lee
    > > > >
    > > >
    > > > So touching the PCI LBB register is the only feasible solution now
    > > > (even though it may not be a clean method) ?
    > > >
    > > > Thanks,
    > > > Pradeep Subrahmanion
    > >
    > > That will be better leave LBB register only touched by i915 driver.
    > >
    > > If 'acpi_backlight=vendor' works to you, maybe we can add a quirk to
    > > video_detect.c.
    > > You can try the following patch.
    >
    > Thanks . I tried your patch .acpi_backlight=vendor allows me to control
    > brightness with hot key.But there are problems with it like increasing

    OK, thanks for your testing, I will send out patch and add Cc. to you.

    > brightness after maximum level causes blank screen.So I am trying it
    > sort it out.
    >
    > Thank you ,
    >
    > Pradeep Subrahmanion
    >

    For the maximum level causes blank screen...

    Please kindly help to identify which driver handle the brightness
    change, run the following 2 commands:

    # echo 5 > /sys/class/backlight/acer-wmi/brightness
    # echo 5 > /sys/class/backlight/intel_backlight/brightness

    Which one works to change brightness on your machine?


    Thanks a lot!
    Joey Lee

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