On Mon, Oct 06, 2014 at 09:22:44PM +0200, Markus Pargmann wrote: > The backlight will be enabled by the panel again if it is used. So we > can save the default brightness and disable the pwm backlight when > probing. > > Signed-off-by: Markus Pargmann <mpa@xxxxxxxxxxxxxx> > --- > drivers/video/backlight/pwm_bl.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c > index 336b83be7e2d..b4f433a6f106 100644 > --- a/drivers/video/backlight/pwm_bl.c > +++ b/drivers/video/backlight/pwm_bl.c > @@ -317,9 +317,11 @@ static int pwm_backlight_probe(struct platform_device *pdev) > data->dft_brightness = data->max_brightness; > } > > - bl->props.brightness = data->dft_brightness; > + bl->props.brightness = 0; > backlight_update_status(bl); > > + bl->props.brightness = data->dft_brightness; > + > platform_set_drvdata(pdev, bl); > return 0; > It would be nice if it was that easy. But we can't do this, because it will regress for users of this driver that don't use a panel or DRM. If the PWM backlight driver is used for example in conjunction with a plain fbdev driver it isn't necessarily hooked up with anything and won't be enabled automatically. That's really bad if fbdev is the only output you have since you'd have to blindly type the commands to enable the backlight. Furthermore disabling backlight isn't always what you want to do. For example if the bootloader already turned it on and you hand over from bootloader to kernel in a seamless way, then you absolutely want to keep backlight on all the time. See also[0] for a different proposal to solve the same problem. Back at the time that received only a very few replies, but it would be nice if Lee and Bryan could look at it again and see if we can come up with some way to deal with this situation. Thierry [0]: https://lkml.org/lkml/2014/7/31/259
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