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    SubjectRe: [PATCH 0/3] Generic sysfs support for ACPI ALS and other ALS devices
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    On Thu, 2009-08-06 at 15:13 +0800, Pavel Machek wrote:
    > > > > No,
    > > > > For a ALS policy, user space should set a brightness level as the base
    > > > > point, i.e. the backlight when display adjustment is 100.
    > > > > and then uses the adjustment values gotten from this mappings to
    > > > > calculate the actual brightness level the display should be put in.
    > > >
    > > > Ok, so just make the code return only the "adjustement" -- userspace
    > > > does not really need to know "illuminance" and you can do the mapping
    > > > in the kernel AFAICT.
    > > >
    > >
    > > ALS exports
    > > 1. the current ambient light illuminance
    > > 2. the mappings
    > >
    > > Backlight device exports
    > > 1. the brightness levels.
    > >
    > > User space needs to:
    > > 1. set a brightness level as the base point
    > > 2. read the current ambient light illuminance from ALS device
    > > 3. read the ambient light illuminance to display adjustment mappings
    > > 4. calculate a proper brightness level we should set.
    > >
    > > For example, if we set brightness 6 as the default brightness, i.e. the
    > > brightness level when ambient light illuminance is 300.
    > > Now we walk outdoors, and the current illuminance is 1000,
    > > then we should set the new_brightness_level to (6 * 150%)
    >
    > Yes, so just export
    >
    > ALS exports
    > 1. the current ambient light illuminance
    > 2. the current mapped ambient light illuminance
    >
    In fact, only one attribute is enough.
    The ALS driver can query the current illuminance, parse the mapping and
    only export the display luminance adjustment values to user space.

    > Backlight device exports
    > 1. the brightness levels.
    >
    > User space needs to:
    > 1. set a brightness level as the base point
    > 2. read the current mapped ambient light illuminance from ALS device
    > 3. calculate a proper brightness level we should set.
    >
    then user space just needs to
    1. set a brightness level as the base point
    2. get the display adjustment value and calculate a proper brightness
    level at any time.

    this is easier, but it makes me feel that this doesn't look like an
    _ALS_ device any more.
    We still should export some ALS properties to user space, shouldn't we?

    Could you please look at the documentation about ALS sysfs class in the
    patch I sent out just now, and comment on that one please? thanks!

    thanks,
    rui




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