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[PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and use_count during pwm_backlight_probe()

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  [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and use_count during pwm_backlight_probe() Lukasz Majewski <l.majewski@majess.pl> - 2016-11-01 08:30 +0100
    Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and  use_count during pwm_backlight_probe() Lukasz Majewski <l.majewski@majess.pl> - 2016-11-08 23:50 +0100
      Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and  use_count during pwm_backlight_probe() Lee Jones <lee.jones@linaro.org> - 2016-11-09 16:00 +0100
        Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and  use_count during pwm_backlight_probe() Lukasz Majewski <l.majewski@majess.pl> - 2016-11-09 22:10 +0100
          Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and  use_count during pwm_backlight_probe() Lee Jones <lee.jones@linaro.org> - 2016-11-10 08:50 +0100
      Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and  use_count during pwm_backlight_probe() Lee Jones <lee.jones@linaro.org> - 2016-11-10 09:20 +0100
        Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and  use_count during pwm_backlight_probe() Lukasz Majewski <l.majewski@majess.pl> - 2016-11-11 00:30 +0100
    Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and  use_count during pwm_backlight_probe() Lee Jones <lee.jones@linaro.org> - 2016-11-10 09:20 +0100

#1513136 — [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and use_count during pwm_backlight_probe()

The commit a55944ca82d2 ("backlight: update bd state & fb_blank properties
when necessary") has posed some extra restrictions on blanking and 
unblanking frame buffer device.

Unfortunately, pwm_bl driver's probe did not initialize members of
struct backlight_device necessary for further blank/unblank operation.

This code in case of initial unblank of backlight device (default 
behaviour) sets use_count to 1 and marks this particular backlight device
as used by all available fb devices (since it is not known during probe 
how much and which fb devices will be assigned).

Without this code, the backlight works properly until one tries to blank
it manually from sysfs with "echo 1 > /sys/class/graphics/fb0/blank".
Since fb_bl_on[0] and use_count were both set to 0, the logic at
fb_notifier_callback (@backlight.c) thought that we didn't turn on
(unblanked) the backlight device and refuses to disable (blank) it.
As a result we see garbage from fb displayed.

Signed-off-by: Lukasz Majewski <l.majewski@majess.pl>
---
The patch has been tested on i.MX6q with 4.9-rc3
SHA1: a909d3e636995ba7c349e2ca5dbb528154d4ac30
---
Changes for v2:
- Update commit message with proper other commit reference

---
 drivers/video/backlight/pwm_bl.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 1261400..6859ba0 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -202,7 +202,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 	struct pwm_bl_data *pb;
 	int initial_blank = FB_BLANK_UNBLANK;
 	struct pwm_args pargs;
-	int ret;
+	int ret, i;
 
 	if (!data) {
 		ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
@@ -348,6 +348,14 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 
 	bl->props.brightness = data->dft_brightness;
 	bl->props.power = initial_blank;
+
+	if (initial_blank == FB_BLANK_UNBLANK) {
+		for (i = 0; i < FB_MAX; i++)
+			bl->fb_bl_on[i] = true;
+
+		bl->use_count = 1;
+	}
+
 	backlight_update_status(bl);
 
 	platform_set_drvdata(pdev, bl);
-- 
2.1.4

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#1517624 — Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and use_count during pwm_backlight_probe()

[Multipart message — attachments visible in raw view] — view raw

Dear All,

> The commit a55944ca82d2 ("backlight: update bd state & fb_blank
> properties when necessary") has posed some extra restrictions on
> blanking and unblanking frame buffer device.
> 
> Unfortunately, pwm_bl driver's probe did not initialize members of
> struct backlight_device necessary for further blank/unblank operation.
> 
> This code in case of initial unblank of backlight device (default 
> behaviour) sets use_count to 1 and marks this particular backlight
> device as used by all available fb devices (since it is not known
> during probe how much and which fb devices will be assigned).
> 
> Without this code, the backlight works properly until one tries to
> blank it manually from sysfs with "echo 1
> > /sys/class/graphics/fb0/blank". Since fb_bl_on[0] and use_count
> > were both set to 0, the logic at
> fb_notifier_callback (@backlight.c) thought that we didn't turn on
> (unblanked) the backlight device and refuses to disable (blank) it.
> As a result we see garbage from fb displayed.

COmments/acks are more than welcome :-)

Best regards,
Łukasz Majewski

> 
> Signed-off-by: Lukasz Majewski <l.majewski@majess.pl>
> ---
> The patch has been tested on i.MX6q with 4.9-rc3
> SHA1: a909d3e636995ba7c349e2ca5dbb528154d4ac30
> ---
> Changes for v2:
> - Update commit message with proper other commit reference
> 
> ---
>  drivers/video/backlight/pwm_bl.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/video/backlight/pwm_bl.c
> b/drivers/video/backlight/pwm_bl.c index 1261400..6859ba0 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -202,7 +202,7 @@ static int pwm_backlight_probe(struct
> platform_device *pdev) struct pwm_bl_data *pb;
>  	int initial_blank = FB_BLANK_UNBLANK;
>  	struct pwm_args pargs;
> -	int ret;
> +	int ret, i;
>  
>  	if (!data) {
>  		ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
> @@ -348,6 +348,14 @@ static int pwm_backlight_probe(struct
> platform_device *pdev) 
>  	bl->props.brightness = data->dft_brightness;
>  	bl->props.power = initial_blank;
> +
> +	if (initial_blank == FB_BLANK_UNBLANK) {
> +		for (i = 0; i < FB_MAX; i++)
> +			bl->fb_bl_on[i] = true;
> +
> +		bl->use_count = 1;
> +	}
> +
>  	backlight_update_status(bl);
>  
>  	platform_set_drvdata(pdev, bl);

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#1518230 — Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and use_count during pwm_backlight_probe()

On Tue, 08 Nov 2016, Lukasz Majewski wrote:

> Dear All,
> 
> > The commit a55944ca82d2 ("backlight: update bd state & fb_blank
> > properties when necessary") has posed some extra restrictions on
> > blanking and unblanking frame buffer device.
> > 
> > Unfortunately, pwm_bl driver's probe did not initialize members of
> > struct backlight_device necessary for further blank/unblank operation.
> > 
> > This code in case of initial unblank of backlight device (default 
> > behaviour) sets use_count to 1 and marks this particular backlight
> > device as used by all available fb devices (since it is not known
> > during probe how much and which fb devices will be assigned).
> > 
> > Without this code, the backlight works properly until one tries to
> > blank it manually from sysfs with "echo 1
> > > /sys/class/graphics/fb0/blank". Since fb_bl_on[0] and use_count
> > > were both set to 0, the logic at
> > fb_notifier_callback (@backlight.c) thought that we didn't turn on
> > (unblanked) the backlight device and refuses to disable (blank) it.
> > As a result we see garbage from fb displayed.
> 
> COmments/acks are more than welcome :-)

I thought Jingoo already replied to you?

> > Signed-off-by: Lukasz Majewski <l.majewski@majess.pl>
> > ---
> > The patch has been tested on i.MX6q with 4.9-rc3
> > SHA1: a909d3e636995ba7c349e2ca5dbb528154d4ac30
> > ---
> > Changes for v2:
> > - Update commit message with proper other commit reference
> > 
> > ---
> >  drivers/video/backlight/pwm_bl.c | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/video/backlight/pwm_bl.c
> > b/drivers/video/backlight/pwm_bl.c index 1261400..6859ba0 100644
> > --- a/drivers/video/backlight/pwm_bl.c
> > +++ b/drivers/video/backlight/pwm_bl.c
> > @@ -202,7 +202,7 @@ static int pwm_backlight_probe(struct
> > platform_device *pdev) struct pwm_bl_data *pb;
> >  	int initial_blank = FB_BLANK_UNBLANK;
> >  	struct pwm_args pargs;
> > -	int ret;
> > +	int ret, i;
> >  
> >  	if (!data) {
> >  		ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
> > @@ -348,6 +348,14 @@ static int pwm_backlight_probe(struct
> > platform_device *pdev) 
> >  	bl->props.brightness = data->dft_brightness;
> >  	bl->props.power = initial_blank;
> > +
> > +	if (initial_blank == FB_BLANK_UNBLANK) {
> > +		for (i = 0; i < FB_MAX; i++)
> > +			bl->fb_bl_on[i] = true;
> > +
> > +		bl->use_count = 1;
> > +	}
> > +
> >  	backlight_update_status(bl);
> >  
> >  	platform_set_drvdata(pdev, bl);
> 



-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

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#1518481 — Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and use_count during pwm_backlight_probe()

[Multipart message — attachments visible in raw view] — view raw

Hi Lee,

> On Tue, 08 Nov 2016, Lukasz Majewski wrote:
> 
> > Dear All,
> > 
> > > The commit a55944ca82d2 ("backlight: update bd state & fb_blank
> > > properties when necessary") has posed some extra restrictions on
> > > blanking and unblanking frame buffer device.
> > > 
> > > Unfortunately, pwm_bl driver's probe did not initialize members of
> > > struct backlight_device necessary for further blank/unblank
> > > operation.
> > > 
> > > This code in case of initial unblank of backlight device (default 
> > > behaviour) sets use_count to 1 and marks this particular backlight
> > > device as used by all available fb devices (since it is not known
> > > during probe how much and which fb devices will be assigned).
> > > 
> > > Without this code, the backlight works properly until one tries to
> > > blank it manually from sysfs with "echo 1
> > > > /sys/class/graphics/fb0/blank". Since fb_bl_on[0] and use_count
> > > > were both set to 0, the logic at
> > > fb_notifier_callback (@backlight.c) thought that we didn't turn on
> > > (unblanked) the backlight device and refuses to disable (blank)
> > > it. As a result we see garbage from fb displayed.
> > 
> > COmments/acks are more than welcome :-)
> 
> I thought Jingoo already replied to you?

Yes, Jingoo replied to me and asked for correcting the patch
description. The corrected patch is the v2.


Best regards,
Łukasz Majewski

> 
> > > Signed-off-by: Lukasz Majewski <l.majewski@majess.pl>
> > > ---
> > > The patch has been tested on i.MX6q with 4.9-rc3
> > > SHA1: a909d3e636995ba7c349e2ca5dbb528154d4ac30
> > > ---
> > > Changes for v2:
> > > - Update commit message with proper other commit reference
> > > 
> > > ---
> > >  drivers/video/backlight/pwm_bl.c | 10 +++++++++-
> > >  1 file changed, 9 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/video/backlight/pwm_bl.c
> > > b/drivers/video/backlight/pwm_bl.c index 1261400..6859ba0 100644
> > > --- a/drivers/video/backlight/pwm_bl.c
> > > +++ b/drivers/video/backlight/pwm_bl.c
> > > @@ -202,7 +202,7 @@ static int pwm_backlight_probe(struct
> > > platform_device *pdev) struct pwm_bl_data *pb;
> > >  	int initial_blank = FB_BLANK_UNBLANK;
> > >  	struct pwm_args pargs;
> > > -	int ret;
> > > +	int ret, i;
> > >  
> > >  	if (!data) {
> > >  		ret = pwm_backlight_parse_dt(&pdev->dev,
> > > &defdata); @@ -348,6 +348,14 @@ static int
> > > pwm_backlight_probe(struct platform_device *pdev) 
> > >  	bl->props.brightness = data->dft_brightness;
> > >  	bl->props.power = initial_blank;
> > > +
> > > +	if (initial_blank == FB_BLANK_UNBLANK) {
> > > +		for (i = 0; i < FB_MAX; i++)
> > > +			bl->fb_bl_on[i] = true;
> > > +
> > > +		bl->use_count = 1;
> > > +	}
> > > +
> > >  	backlight_update_status(bl);
> > >  
> > >  	platform_set_drvdata(pdev, bl);
> > 
> 
> 
> 

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#1518720 — Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and use_count during pwm_backlight_probe()

On Wed, 09 Nov 2016, Lukasz Majewski wrote:

> Hi Lee,
> 
> > On Tue, 08 Nov 2016, Lukasz Majewski wrote:
> > 
> > > Dear All,
> > > 
> > > > The commit a55944ca82d2 ("backlight: update bd state & fb_blank
> > > > properties when necessary") has posed some extra restrictions on
> > > > blanking and unblanking frame buffer device.
> > > > 
> > > > Unfortunately, pwm_bl driver's probe did not initialize members of
> > > > struct backlight_device necessary for further blank/unblank
> > > > operation.
> > > > 
> > > > This code in case of initial unblank of backlight device (default 
> > > > behaviour) sets use_count to 1 and marks this particular backlight
> > > > device as used by all available fb devices (since it is not known
> > > > during probe how much and which fb devices will be assigned).
> > > > 
> > > > Without this code, the backlight works properly until one tries to
> > > > blank it manually from sysfs with "echo 1
> > > > > /sys/class/graphics/fb0/blank". Since fb_bl_on[0] and use_count
> > > > > were both set to 0, the logic at
> > > > fb_notifier_callback (@backlight.c) thought that we didn't turn on
> > > > (unblanked) the backlight device and refuses to disable (blank)
> > > > it. As a result we see garbage from fb displayed.
> > > 
> > > COmments/acks are more than welcome :-)
> > 
> > I thought Jingoo already replied to you?
> 
> Yes, Jingoo replied to me and asked for correcting the patch
> description. The corrected patch is the v2.

Ah, I see.  You've attached the v4 to the original set.

Ball is in Jingoo's court.

> > > > Signed-off-by: Lukasz Majewski <l.majewski@majess.pl>
> > > > ---
> > > > The patch has been tested on i.MX6q with 4.9-rc3
> > > > SHA1: a909d3e636995ba7c349e2ca5dbb528154d4ac30
> > > > ---
> > > > Changes for v2:
> > > > - Update commit message with proper other commit reference
> > > > 
> > > > ---
> > > >  drivers/video/backlight/pwm_bl.c | 10 +++++++++-
> > > >  1 file changed, 9 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/video/backlight/pwm_bl.c
> > > > b/drivers/video/backlight/pwm_bl.c index 1261400..6859ba0 100644
> > > > --- a/drivers/video/backlight/pwm_bl.c
> > > > +++ b/drivers/video/backlight/pwm_bl.c
> > > > @@ -202,7 +202,7 @@ static int pwm_backlight_probe(struct
> > > > platform_device *pdev) struct pwm_bl_data *pb;
> > > >  	int initial_blank = FB_BLANK_UNBLANK;
> > > >  	struct pwm_args pargs;
> > > > -	int ret;
> > > > +	int ret, i;
> > > >  
> > > >  	if (!data) {
> > > >  		ret = pwm_backlight_parse_dt(&pdev->dev,
> > > > &defdata); @@ -348,6 +348,14 @@ static int
> > > > pwm_backlight_probe(struct platform_device *pdev) 
> > > >  	bl->props.brightness = data->dft_brightness;
> > > >  	bl->props.power = initial_blank;
> > > > +
> > > > +	if (initial_blank == FB_BLANK_UNBLANK) {
> > > > +		for (i = 0; i < FB_MAX; i++)
> > > > +			bl->fb_bl_on[i] = true;
> > > > +
> > > > +		bl->use_count = 1;
> > > > +	}
> > > > +
> > > >  	backlight_update_status(bl);
> > > >  
> > > >  	platform_set_drvdata(pdev, bl);
> > > 
> > 
> > 
> > 
> 



-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

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#1518733 — Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and use_count during pwm_backlight_probe()

On Tue, 08 Nov 2016, Lukasz Majewski wrote:

> Dear All,
> 
> > The commit a55944ca82d2 ("backlight: update bd state & fb_blank
> > properties when necessary") has posed some extra restrictions on
> > blanking and unblanking frame buffer device.
> > 
> > Unfortunately, pwm_bl driver's probe did not initialize members of
> > struct backlight_device necessary for further blank/unblank operation.
> > 
> > This code in case of initial unblank of backlight device (default 
> > behaviour) sets use_count to 1 and marks this particular backlight
> > device as used by all available fb devices (since it is not known
> > during probe how much and which fb devices will be assigned).
> > 
> > Without this code, the backlight works properly until one tries to
> > blank it manually from sysfs with "echo 1
> > > /sys/class/graphics/fb0/blank". Since fb_bl_on[0] and use_count
> > > were both set to 0, the logic at
> > fb_notifier_callback (@backlight.c) thought that we didn't turn on
> > (unblanked) the backlight device and refuses to disable (blank) it.
> > As a result we see garbage from fb displayed.
> 
> COmments/acks are more than welcome :-)

Ah, it looks like you dropped Jingoo from the list!

I'll reply to the original mail with him in CC.

> > Signed-off-by: Lukasz Majewski <l.majewski@majess.pl>
> > ---
> > The patch has been tested on i.MX6q with 4.9-rc3
> > SHA1: a909d3e636995ba7c349e2ca5dbb528154d4ac30
> > ---
> > Changes for v2:
> > - Update commit message with proper other commit reference
> > 
> > ---
> >  drivers/video/backlight/pwm_bl.c | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/video/backlight/pwm_bl.c
> > b/drivers/video/backlight/pwm_bl.c index 1261400..6859ba0 100644
> > --- a/drivers/video/backlight/pwm_bl.c
> > +++ b/drivers/video/backlight/pwm_bl.c
> > @@ -202,7 +202,7 @@ static int pwm_backlight_probe(struct
> > platform_device *pdev) struct pwm_bl_data *pb;
> >  	int initial_blank = FB_BLANK_UNBLANK;
> >  	struct pwm_args pargs;
> > -	int ret;
> > +	int ret, i;
> >  
> >  	if (!data) {
> >  		ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
> > @@ -348,6 +348,14 @@ static int pwm_backlight_probe(struct
> > platform_device *pdev) 
> >  	bl->props.brightness = data->dft_brightness;
> >  	bl->props.power = initial_blank;
> > +
> > +	if (initial_blank == FB_BLANK_UNBLANK) {
> > +		for (i = 0; i < FB_MAX; i++)
> > +			bl->fb_bl_on[i] = true;
> > +
> > +		bl->use_count = 1;
> > +	}
> > +
> >  	backlight_update_status(bl);
> >  
> >  	platform_set_drvdata(pdev, bl);
> 



-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

[toc] | [prev] | [next] | [standalone]

#1519440 — Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and use_count during pwm_backlight_probe()

[Multipart message — attachments visible in raw view] — view raw

Dear Lee,

> On Tue, 08 Nov 2016, Lukasz Majewski wrote:
> 
> > Dear All,
> > 
> > > The commit a55944ca82d2 ("backlight: update bd state & fb_blank
> > > properties when necessary") has posed some extra restrictions on
> > > blanking and unblanking frame buffer device.
> > > 
> > > Unfortunately, pwm_bl driver's probe did not initialize members of
> > > struct backlight_device necessary for further blank/unblank
> > > operation.
> > > 
> > > This code in case of initial unblank of backlight device (default 
> > > behaviour) sets use_count to 1 and marks this particular backlight
> > > device as used by all available fb devices (since it is not known
> > > during probe how much and which fb devices will be assigned).
> > > 
> > > Without this code, the backlight works properly until one tries to
> > > blank it manually from sysfs with "echo 1
> > > > /sys/class/graphics/fb0/blank". Since fb_bl_on[0] and use_count
> > > > were both set to 0, the logic at
> > > fb_notifier_callback (@backlight.c) thought that we didn't turn on
> > > (unblanked) the backlight device and refuses to disable (blank)
> > > it. As a result we see garbage from fb displayed.
> > 
> > COmments/acks are more than welcome :-)
> 
> Ah, it looks like you dropped Jingoo from the list!
> 

I can only apologize for such situation.... strange mistake.

> I'll reply to the original mail with him in CC.

Thank you for your help.

Best regards,
Lukasz Majewski

> 
> > > Signed-off-by: Lukasz Majewski <l.majewski@majess.pl>
> > > ---
> > > The patch has been tested on i.MX6q with 4.9-rc3
> > > SHA1: a909d3e636995ba7c349e2ca5dbb528154d4ac30
> > > ---
> > > Changes for v2:
> > > - Update commit message with proper other commit reference
> > > 
> > > ---
> > >  drivers/video/backlight/pwm_bl.c | 10 +++++++++-
> > >  1 file changed, 9 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/video/backlight/pwm_bl.c
> > > b/drivers/video/backlight/pwm_bl.c index 1261400..6859ba0 100644
> > > --- a/drivers/video/backlight/pwm_bl.c
> > > +++ b/drivers/video/backlight/pwm_bl.c
> > > @@ -202,7 +202,7 @@ static int pwm_backlight_probe(struct
> > > platform_device *pdev) struct pwm_bl_data *pb;
> > >  	int initial_blank = FB_BLANK_UNBLANK;
> > >  	struct pwm_args pargs;
> > > -	int ret;
> > > +	int ret, i;
> > >  
> > >  	if (!data) {
> > >  		ret = pwm_backlight_parse_dt(&pdev->dev,
> > > &defdata); @@ -348,6 +348,14 @@ static int
> > > pwm_backlight_probe(struct platform_device *pdev) 
> > >  	bl->props.brightness = data->dft_brightness;
> > >  	bl->props.power = initial_blank;
> > > +
> > > +	if (initial_blank == FB_BLANK_UNBLANK) {
> > > +		for (i = 0; i < FB_MAX; i++)
> > > +			bl->fb_bl_on[i] = true;
> > > +
> > > +		bl->use_count = 1;
> > > +	}
> > > +
> > >  	backlight_update_status(bl);
> > >  
> > >  	platform_set_drvdata(pdev, bl);
> > 
> 
> 
> 

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#1518736 — Re: [PATCH v2] video: backlight: pwm_bl: Initialize fb_bl_on[x] and use_count during pwm_backlight_probe()

Adding Jingoo.

On Tue, 01 Nov 2016, Lukasz Majewski wrote:
> The commit a55944ca82d2 ("backlight: update bd state & fb_blank properties
> when necessary") has posed some extra restrictions on blanking and 
> unblanking frame buffer device.
> 
> Unfortunately, pwm_bl driver's probe did not initialize members of
> struct backlight_device necessary for further blank/unblank operation.
> 
> This code in case of initial unblank of backlight device (default 
> behaviour) sets use_count to 1 and marks this particular backlight device
> as used by all available fb devices (since it is not known during probe 
> how much and which fb devices will be assigned).
> 
> Without this code, the backlight works properly until one tries to blank
> it manually from sysfs with "echo 1 > /sys/class/graphics/fb0/blank".
> Since fb_bl_on[0] and use_count were both set to 0, the logic at
> fb_notifier_callback (@backlight.c) thought that we didn't turn on
> (unblanked) the backlight device and refuses to disable (blank) it.
> As a result we see garbage from fb displayed.
> 
> Signed-off-by: Lukasz Majewski <l.majewski@majess.pl>
> ---
> The patch has been tested on i.MX6q with 4.9-rc3
> SHA1: a909d3e636995ba7c349e2ca5dbb528154d4ac30
> ---
> Changes for v2:
> - Update commit message with proper other commit reference
> 
> ---
>  drivers/video/backlight/pwm_bl.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index 1261400..6859ba0 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -202,7 +202,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  	struct pwm_bl_data *pb;
>  	int initial_blank = FB_BLANK_UNBLANK;
>  	struct pwm_args pargs;
> -	int ret;
> +	int ret, i;
>  
>  	if (!data) {
>  		ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
> @@ -348,6 +348,14 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  
>  	bl->props.brightness = data->dft_brightness;
>  	bl->props.power = initial_blank;
> +
> +	if (initial_blank == FB_BLANK_UNBLANK) {
> +		for (i = 0; i < FB_MAX; i++)
> +			bl->fb_bl_on[i] = true;
> +
> +		bl->use_count = 1;
> +	}
> +
>  	backlight_update_status(bl);
>  
>  	platform_set_drvdata(pdev, bl);

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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