From mboxrd@z Thu Jan 1 00:00:00 1970 From: ajaynumb@gmail.com (Ajay kumar) Date: Tue, 7 Oct 2014 14:47:53 +0530 Subject: [PATCH] pwm-backlight: Turn off pwm backlight in probe In-Reply-To: <20141007090718.GC5042@pengutronix.de> References: <1412623364-14583-1-git-send-email-mpa@pengutronix.de> <20141007083548.GD24254@ulmo> <20141007090718.GC5042@pengutronix.de> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Oct 7, 2014 at 2:37 PM, Markus Pargmann wrote: > Hi, > > On Tue, Oct 07, 2014 at 10:35:49AM +0200, Thierry Reding wrote: >> 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 >> > --- >> > 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. > > Yes your proposal looks a lot better to handle the different use cases. > The DT-binding is not a hardware description but I don't see any better > way of passing that information. So it would be good to get your > solution mainline. +1 And, I have already tested Thierry's proposal on Exynos5800 peach_pi. Ajay