Eric Lee / smarc-fsl-linux-kernel

26 Aug, 2011

1 commit

23 Mar, 2011

1 commit

  • ef0a5e80f   pwm_backlight: add check_fb() hook ... Browse Code »

    In systems with multiple framebuffer devices, one of the devices might be
    blanked while another is unblanked. In order for the backlight blanking
    logic to know whether to turn off the backlight for a particular
    framebuffer's blanking notification, it needs to be able to check if a
    given framebuffer device corresponds to the backlight.

    This plumbs the check_fb hook from core backlight through the
    pwm_backlight helper to allow platform code to plug in a check_fb hook.

    Signed-off-by: Robert Morell
    Cc: Richard Purdie
    Cc: Arun Murthy
    Cc: Linus Walleij
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Robert Morell
     

12 Nov, 2010

1 commit

  • fef7764f8   backlight: add low threshold to pwm backlight ... Browse Code »

    The intensity of the backlight can be varied from a range of
    max_brightness to zero. Though most, if not all the pwm based backlight
    devices start flickering at lower brightness value. And also for each
    device there exists a brightness value below which the backlight appears
    to be turned off though the value is not equal to zero.

    If the range of brightness for a device is from zero to max_brightness. A
    graph is plotted for brightness Vs intensity for the pwm based backlight
    device has to be a linear graph.

    intensity
    | /
    | /
    | /
    |/
    ---------
    0 max_brightness

    But pratically on measuring the above we note that the intensity of
    backlight goes to zero(OFF) when the value in not zero almost nearing to
    zero(some x%). so the graph looks like

    intensity
    | /
    | /
    | /
    | |
    ------------
    0 x max_brightness

    In order to overcome this drawback knowing this x% i.e nothing but the low
    threshold beyond which the backlight is off and will have no effect, the
    brightness value is being offset by the low threshold value(retaining the
    linearity of the graph). Now the graph becomes

    intensity
    | /
    | /
    | /
    | /
    -------------
    0 max_brightness

    With this for each and every digit increment in the brightness from zero
    there is a change in the intensity of backlight. Devices having this
    behaviour can set the low threshold brightness(lth_brightness) and pass
    the same as platform data else can have it as zero.

    [akpm@linux-foundation.org: coding-style fixes]
    Signed-off-by: Arun Murthy
    Acked-by: Linus Walleij
    Acked-by: Richard Purdie
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Arun Murthy
     

17 Dec, 2009

1 commit

03 Jul, 2008

2 commits