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    SubjectRe: [patch] added brightness feature to lcd class.
    On Mon, 2009-11-02 at 17:50 +0900, InKi Dae wrote:
    > This patch adds brightness feature to lcd class.
    > (kernel/driver/video/backlight/lcd.c)
    > In the past, most of the lcd panels for embedded system was TFT-LCD
    > Panel needing backlight device.
    > But now AMOLED LCD Panel appeared so we should consider brightness
    > control for AMOLED Panel.
    > For the time being, I used backlight fake driver for brightness
    > control of AMOLED LCD Panel.
    > But this way is not good, so I propose to add brightness feature to lcd class.
    > For this, I attached patch file and if my proposal is approved
    > Then I will send s6e63m0 and tl2796 AMOLED lcd panel driver based on
    > lcd class modified soon.

    Pavel has a good point but let me try and explain it differently.

    The point of the backlight class is to expose a backlight brightness
    control to userspace in a consistent well defined way. Anyone wishing to
    write a piece of software to control the brightness of a backlight then
    only needs to support *one* interface.

    It is entirely accepted and normal that multiple "class" devices may
    appear in userspace for one piece of physical hardware.

    Your patch duplicates a userspace API and means any backlight
    application would have to look for *two* different interfaces. This is

    Why can't your driver just register a backlight interface and an LCD
    interface? I'd imagine your backlight and LCD can be powered on/off
    separately too.

    Please also cc: the backlight/lcd maintainer (me) on backlight/lcd
    patches in future.

    Andrew: Can you drop that patch from -mm please as I'm not convinced we
    need two backlight brightness interfaces around...



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