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    SubjectRe: [PATCH 1/3] backlight: Allow drivers to update the core, and generate events on changes
    On Tue, 2009-07-14 at 20:29 +0800, Richard Purdie wrote:
    > On Mon, 2009-07-13 at 21:41 +0100, Matthew Garrett wrote:
    > > Certain hardware will send us events when the backlight brightness
    > > changes. Add a function to update the value in the core, and
    > > additionally send a uevent so that userspace can pop up appropriate
    > > UI. The uevents are flagged depending on whether the update originated
    > > in the kernel or from userspace, making it easier to only display UI
    > > at the appropriate time.
    > This looks good and I like the idea.
    > My main concern is that we don't start getting bug reports of 'missing'
    > events and have clearly defined expectations of when we see what kind of
    > events. For example, should an event be emitted when low battery causes
    > the backlight to be limited? How about console blanking events turning
    > off the backlight? Are there any other occasions we should be emitting
    > change events and do we need to audit other drivers?
    > I did look to see if we could integrate this more into the backlight
    > core but that doesn't look to be possible unfortunately, at least not
    > without changing the drivers which these patches start.
    > Also, are "userspace" and "kernel" as meaningful as they could be? Would
    > "sysfs" and "hwkeys" make more sense and allow for other future hardware
    > differences? Perhaps someone will tie the backlight to an ambient light
    > sensor for example...

    Hah, I just finished a patch to introduce the ACPI als driver.

    I'm not quite familiar with the status of ALS support in Linux kernel.
    and here is my questions,
    I don't think we have a generic sysfs driver for ALS, i.e. ALS class
    device, right?
    do you guys think it's reasonable to have one?


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