[PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Vladimir Zapolskiy]

Platform PWM backlight data provided by board's device tree should be
complete enough to successfully request a pwm device using pwm_get()
API. This change fixes a bug, when an arbitrary (first found) PWM is
connected to a "pwm-backlight" compatible device, when explicit PWM
device reference is not given.

Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
already describes "pwms" as a required property, instead of blind
selection of a potentially wrong PWM reject legacy PWM device
registration request, leave legacy API only for non-dt cases.

Based on initial implementation done by Dmitry Eremin-Solenikov.

Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
---
The change is based on lee-backlight/for-backlight-next

Changes from v1 to v2:
* rebased on top of Nicolas' commit
    68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")

Links to previous discussions of the change:
* https://patchwork.ozlabs.org/patch/483993/
* https://patchwork.ozlabs.org/patch/398849/

 drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index eff379b..ae3c6b6 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 	}
 
 	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
-	if (IS_ERR(pb->pwm)) {
-		ret = PTR_ERR(pb->pwm);
-		if (ret == -EPROBE_DEFER)
-			goto err_alloc;
-
+	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
+	    && !pdev->dev.of_node) {
 		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 		pb->legacy = true;
 		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
-		if (IS_ERR(pb->pwm)) {
-			dev_err(&pdev->dev, "unable to request legacy PWM\n");
-			ret = PTR_ERR(pb->pwm);
-			goto err_alloc;
-		}
+	}
+
+	if (IS_ERR(pb->pwm)) {
+		ret = PTR_ERR(pb->pwm);
+		if (ret != -EPROBE_DEFER)
+			dev_err(&pdev->dev, "unable to request PWM\n");
+		goto err_alloc;
 	}
 
 	dev_dbg(&pdev->dev, "got pwm for backlight\n");
-- 
2.5.0

[PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Vladimir Zapolskiy]

Platform PWM backlight data provided by board's device tree should be
complete enough to successfully request a pwm device using pwm_get()
API. This change fixes a bug, when an arbitrary (first found) PWM is
connected to a "pwm-backlight" compatible device, when explicit PWM
device reference is not given.

Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
already describes "pwms" as a required property, instead of blind
selection of a potentially wrong PWM reject legacy PWM device
registration request, leave legacy API only for non-dt cases.

Based on initial implementation done by Dmitry Eremin-Solenikov.

Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
---
The change is based on lee-backlight/for-backlight-next

Changes from v1 to v2:
* rebased on top of Nicolas' commit
    68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")

Links to previous discussions of the change:
* https://patchwork.ozlabs.org/patch/483993/
* https://patchwork.ozlabs.org/patch/398849/

 drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index eff379b..ae3c6b6 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 	}
 
 	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
-	if (IS_ERR(pb->pwm)) {
-		ret = PTR_ERR(pb->pwm);
-		if (ret = -EPROBE_DEFER)
-			goto err_alloc;
-
+	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
+	    && !pdev->dev.of_node) {
 		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
 		pb->legacy = true;
 		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
-		if (IS_ERR(pb->pwm)) {
-			dev_err(&pdev->dev, "unable to request legacy PWM\n");
-			ret = PTR_ERR(pb->pwm);
-			goto err_alloc;
-		}
+	}
+
+	if (IS_ERR(pb->pwm)) {
+		ret = PTR_ERR(pb->pwm);
+		if (ret != -EPROBE_DEFER)
+			dev_err(&pdev->dev, "unable to request PWM\n");
+		goto err_alloc;
 	}
 
 	dev_dbg(&pdev->dev, "got pwm for backlight\n");
-- 
2.5.0

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Nicolas Ferre]

Le 12/10/2015 14:29, Vladimir Zapolskiy a écrit :
> Platform PWM backlight data provided by board's device tree should be
> complete enough to successfully request a pwm device using pwm_get()
> API. This change fixes a bug, when an arbitrary (first found) PWM is
> connected to a "pwm-backlight" compatible device, when explicit PWM
> device reference is not given.
> 
> Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> already describes "pwms" as a required property, instead of blind
> selection of a potentially wrong PWM reject legacy PWM device
> registration request, leave legacy API only for non-dt cases.
> 
> Based on initial implementation done by Dmitry Eremin-Solenikov.
> 
> Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
> Acked-by: Thierry Reding <thierry.reding@gmail.com>
> Acked-by: Lee Jones <lee.jones@linaro.org>

It seems good to me:
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>

(Adding some people to the Cc: list).


> ---
> The change is based on lee-backlight/for-backlight-next
> 
> Changes from v1 to v2:
> * rebased on top of Nicolas' commit
>     68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
> 
> Links to previous discussions of the change:
> * https://patchwork.ozlabs.org/patch/483993/
> * https://patchwork.ozlabs.org/patch/398849/
> 
>  drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
>  1 file changed, 9 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index eff379b..ae3c6b6 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  	}
>  
>  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
> -	if (IS_ERR(pb->pwm)) {
> -		ret = PTR_ERR(pb->pwm);
> -		if (ret == -EPROBE_DEFER)
> -			goto err_alloc;
> -
> +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
> +	    && !pdev->dev.of_node) {
>  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
>  		pb->legacy = true;
>  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
> -		if (IS_ERR(pb->pwm)) {
> -			dev_err(&pdev->dev, "unable to request legacy PWM\n");
> -			ret = PTR_ERR(pb->pwm);
> -			goto err_alloc;
> -		}
> +	}
> +
> +	if (IS_ERR(pb->pwm)) {
> +		ret = PTR_ERR(pb->pwm);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(&pdev->dev, "unable to request PWM\n");
> +		goto err_alloc;
>  	}
>  
>  	dev_dbg(&pdev->dev, "got pwm for backlight\n");
> 


-- 
Nicolas Ferre

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Nicolas Ferre]

Le 12/10/2015 14:29, Vladimir Zapolskiy a écrit :
> Platform PWM backlight data provided by board's device tree should be
> complete enough to successfully request a pwm device using pwm_get()
> API. This change fixes a bug, when an arbitrary (first found) PWM is
> connected to a "pwm-backlight" compatible device, when explicit PWM
> device reference is not given.
> 
> Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> already describes "pwms" as a required property, instead of blind
> selection of a potentially wrong PWM reject legacy PWM device
> registration request, leave legacy API only for non-dt cases.
> 
> Based on initial implementation done by Dmitry Eremin-Solenikov.
> 
> Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
> Acked-by: Thierry Reding <thierry.reding@gmail.com>
> Acked-by: Lee Jones <lee.jones@linaro.org>

It seems good to me:
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>

(Adding some people to the Cc: list).


> ---
> The change is based on lee-backlight/for-backlight-next
> 
> Changes from v1 to v2:
> * rebased on top of Nicolas' commit
>     68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
> 
> Links to previous discussions of the change:
> * https://patchwork.ozlabs.org/patch/483993/
> * https://patchwork.ozlabs.org/patch/398849/
> 
>  drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
>  1 file changed, 9 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index eff379b..ae3c6b6 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  	}
>  
>  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
> -	if (IS_ERR(pb->pwm)) {
> -		ret = PTR_ERR(pb->pwm);
> -		if (ret = -EPROBE_DEFER)
> -			goto err_alloc;
> -
> +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
> +	    && !pdev->dev.of_node) {
>  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
>  		pb->legacy = true;
>  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
> -		if (IS_ERR(pb->pwm)) {
> -			dev_err(&pdev->dev, "unable to request legacy PWM\n");
> -			ret = PTR_ERR(pb->pwm);
> -			goto err_alloc;
> -		}
> +	}
> +
> +	if (IS_ERR(pb->pwm)) {
> +		ret = PTR_ERR(pb->pwm);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(&pdev->dev, "unable to request PWM\n");
> +		goto err_alloc;
>  	}
>  
>  	dev_dbg(&pdev->dev, "got pwm for backlight\n");
> 


-- 
Nicolas Ferre

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Boris Brezillon]

Hi Vladimir,

On Mon, 12 Oct 2015 15:16:44 +0200
Nicolas Ferre <nicolas.ferre@atmel.com> wrote:

> Le 12/10/2015 14:29, Vladimir Zapolskiy a écrit :
> > Platform PWM backlight data provided by board's device tree should be
> > complete enough to successfully request a pwm device using pwm_get()
> > API. This change fixes a bug, when an arbitrary (first found) PWM is
> > connected to a "pwm-backlight" compatible device, when explicit PWM
> > device reference is not given.
> > 
> > Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> > already describes "pwms" as a required property, instead of blind
> > selection of a potentially wrong PWM reject legacy PWM device
> > registration request, leave legacy API only for non-dt cases.
> > 
> > Based on initial implementation done by Dmitry Eremin-Solenikov.
> > 
> > Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
> > Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
> > Acked-by: Thierry Reding <thierry.reding@gmail.com>
> > Acked-by: Lee Jones <lee.jones@linaro.org>
> 
> It seems good to me:
> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
> 
> (Adding some people to the Cc: list).
> 
> 
> > ---
> > The change is based on lee-backlight/for-backlight-next
> > 
> > Changes from v1 to v2:
> > * rebased on top of Nicolas' commit
> >     68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
> > 
> > Links to previous discussions of the change:
> > * https://patchwork.ozlabs.org/patch/483993/
> > * https://patchwork.ozlabs.org/patch/398849/
> > 
> >  drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
> >  1 file changed, 9 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> > index eff379b..ae3c6b6 100644
> > --- a/drivers/video/backlight/pwm_bl.c
> > +++ b/drivers/video/backlight/pwm_bl.c
> > @@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> >  	}
> >  
> >  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
> > -	if (IS_ERR(pb->pwm)) {
> > -		ret = PTR_ERR(pb->pwm);
> > -		if (ret == -EPROBE_DEFER)
> > -			goto err_alloc;
> > -
> > +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
> > +	    && !pdev->dev.of_node) {
> >  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
> >  		pb->legacy = true;
> >  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
> > -		if (IS_ERR(pb->pwm)) {
> > -			dev_err(&pdev->dev, "unable to request legacy PWM\n");
> > -			ret = PTR_ERR(pb->pwm);
> > -			goto err_alloc;
> > -		}
> > +	}
> > +
> > +	if (IS_ERR(pb->pwm)) {
> > +		ret = PTR_ERR(pb->pwm);
> > +		if (ret != -EPROBE_DEFER)
> > +			dev_err(&pdev->dev, "unable to request PWM\n");
> > +		goto err_alloc;
> >  	}
> >  
> >  	dev_dbg(&pdev->dev, "got pwm for backlight\n");
> > 
> 
> 

I still think it would be cleaner to do what Thierry proposed here [1].
IMO, embedding the complexity of different error cases depending on the
way PWM devices were defined (OF, pdata, ...) is rather risky and
make the code even more complicated.

Best Regards,

Boris

[1]https://lkml.org/lkml/2015/10/5/319


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Boris Brezillon]

Hi Vladimir,

On Mon, 12 Oct 2015 15:16:44 +0200
Nicolas Ferre <nicolas.ferre@atmel.com> wrote:

> Le 12/10/2015 14:29, Vladimir Zapolskiy a écrit :
> > Platform PWM backlight data provided by board's device tree should be
> > complete enough to successfully request a pwm device using pwm_get()
> > API. This change fixes a bug, when an arbitrary (first found) PWM is
> > connected to a "pwm-backlight" compatible device, when explicit PWM
> > device reference is not given.
> > 
> > Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> > already describes "pwms" as a required property, instead of blind
> > selection of a potentially wrong PWM reject legacy PWM device
> > registration request, leave legacy API only for non-dt cases.
> > 
> > Based on initial implementation done by Dmitry Eremin-Solenikov.
> > 
> > Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
> > Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
> > Acked-by: Thierry Reding <thierry.reding@gmail.com>
> > Acked-by: Lee Jones <lee.jones@linaro.org>
> 
> It seems good to me:
> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
> 
> (Adding some people to the Cc: list).
> 
> 
> > ---
> > The change is based on lee-backlight/for-backlight-next
> > 
> > Changes from v1 to v2:
> > * rebased on top of Nicolas' commit
> >     68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
> > 
> > Links to previous discussions of the change:
> > * https://patchwork.ozlabs.org/patch/483993/
> > * https://patchwork.ozlabs.org/patch/398849/
> > 
> >  drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
> >  1 file changed, 9 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> > index eff379b..ae3c6b6 100644
> > --- a/drivers/video/backlight/pwm_bl.c
> > +++ b/drivers/video/backlight/pwm_bl.c
> > @@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> >  	}
> >  
> >  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
> > -	if (IS_ERR(pb->pwm)) {
> > -		ret = PTR_ERR(pb->pwm);
> > -		if (ret = -EPROBE_DEFER)
> > -			goto err_alloc;
> > -
> > +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
> > +	    && !pdev->dev.of_node) {
> >  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
> >  		pb->legacy = true;
> >  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
> > -		if (IS_ERR(pb->pwm)) {
> > -			dev_err(&pdev->dev, "unable to request legacy PWM\n");
> > -			ret = PTR_ERR(pb->pwm);
> > -			goto err_alloc;
> > -		}
> > +	}
> > +
> > +	if (IS_ERR(pb->pwm)) {
> > +		ret = PTR_ERR(pb->pwm);
> > +		if (ret != -EPROBE_DEFER)
> > +			dev_err(&pdev->dev, "unable to request PWM\n");
> > +		goto err_alloc;
> >  	}
> >  
> >  	dev_dbg(&pdev->dev, "got pwm for backlight\n");
> > 
> 
> 

I still think it would be cleaner to do what Thierry proposed here [1].
IMO, embedding the complexity of different error cases depending on the
way PWM devices were defined (OF, pdata, ...) is rather risky and
make the code even more complicated.

Best Regards,

Boris

[1]https://lkml.org/lkml/2015/10/5/319


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Vladimir Zapolskiy]

Hi Boris,

On 12.10.2015 16:30, Boris Brezillon wrote:
> Hi Vladimir,
> 
> On Mon, 12 Oct 2015 15:16:44 +0200
> Nicolas Ferre <nicolas.ferre@atmel.com> wrote:
> 
>> Le 12/10/2015 14:29, Vladimir Zapolskiy a écrit :
>>> Platform PWM backlight data provided by board's device tree should be
>>> complete enough to successfully request a pwm device using pwm_get()
>>> API. This change fixes a bug, when an arbitrary (first found) PWM is
>>> connected to a "pwm-backlight" compatible device, when explicit PWM
>>> device reference is not given.
>>>
>>> Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
>>> already describes "pwms" as a required property, instead of blind
>>> selection of a potentially wrong PWM reject legacy PWM device
>>> registration request, leave legacy API only for non-dt cases.
>>>
>>> Based on initial implementation done by Dmitry Eremin-Solenikov.
>>>
>>> Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
>>> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
>>> Acked-by: Thierry Reding <thierry.reding@gmail.com>
>>> Acked-by: Lee Jones <lee.jones@linaro.org>
>>
>> It seems good to me:
>> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
>>
>> (Adding some people to the Cc: list).
>>
>>
>>> ---
>>> The change is based on lee-backlight/for-backlight-next
>>>
>>> Changes from v1 to v2:
>>> * rebased on top of Nicolas' commit
>>>     68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
>>>
>>> Links to previous discussions of the change:
>>> * https://patchwork.ozlabs.org/patch/483993/
>>> * https://patchwork.ozlabs.org/patch/398849/
>>>
>>>  drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
>>>  1 file changed, 9 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
>>> index eff379b..ae3c6b6 100644
>>> --- a/drivers/video/backlight/pwm_bl.c
>>> +++ b/drivers/video/backlight/pwm_bl.c
>>> @@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>>>  	}
>>>  
>>>  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
>>> -	if (IS_ERR(pb->pwm)) {
>>> -		ret = PTR_ERR(pb->pwm);
>>> -		if (ret == -EPROBE_DEFER)
>>> -			goto err_alloc;
>>> -
>>> +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
>>> +	    && !pdev->dev.of_node) {
>>>  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
>>>  		pb->legacy = true;
>>>  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
>>> -		if (IS_ERR(pb->pwm)) {
>>> -			dev_err(&pdev->dev, "unable to request legacy PWM\n");
>>> -			ret = PTR_ERR(pb->pwm);
>>> -			goto err_alloc;
>>> -		}
>>> +	}
>>> +
>>> +	if (IS_ERR(pb->pwm)) {
>>> +		ret = PTR_ERR(pb->pwm);
>>> +		if (ret != -EPROBE_DEFER)
>>> +			dev_err(&pdev->dev, "unable to request PWM\n");
>>> +		goto err_alloc;
>>>  	}
>>>  
>>>  	dev_dbg(&pdev->dev, "got pwm for backlight\n");
>>>
>>
>>
> 
> I still think it would be cleaner to do what Thierry proposed here [1].
> IMO, embedding the complexity of different error cases depending on the
> way PWM devices were defined (OF, pdata, ...) is rather risky and
> make the code even more complicated.

please correct me if I'm wrong, I suppose Thierry's change fixes
Nicolas' commit 68feaca0b13 only, and the intention of my change is to
fix an absolutely unrelated problem, see the commit message.

So, since still there is a remained chance of getting -EPROBE_DEFER from
pwm_get(), e.g. from of_pwm_get() or failed pwmchip_find_by_name() or
pwm->chip->ops->request() I don't see how Thierry's change alone may
help me to overcome the problem I'm trying to solve here.

> Best Regards,
> 
> Boris
> 
> [1]https://lkml.org/lkml/2015/10/5/319
> 
> 

--
With best wishes,
Vladimir

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Vladimir Zapolskiy]

Hi Boris,

On 12.10.2015 16:30, Boris Brezillon wrote:
> Hi Vladimir,
> 
> On Mon, 12 Oct 2015 15:16:44 +0200
> Nicolas Ferre <nicolas.ferre@atmel.com> wrote:
> 
>> Le 12/10/2015 14:29, Vladimir Zapolskiy a écrit :
>>> Platform PWM backlight data provided by board's device tree should be
>>> complete enough to successfully request a pwm device using pwm_get()
>>> API. This change fixes a bug, when an arbitrary (first found) PWM is
>>> connected to a "pwm-backlight" compatible device, when explicit PWM
>>> device reference is not given.
>>>
>>> Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
>>> already describes "pwms" as a required property, instead of blind
>>> selection of a potentially wrong PWM reject legacy PWM device
>>> registration request, leave legacy API only for non-dt cases.
>>>
>>> Based on initial implementation done by Dmitry Eremin-Solenikov.
>>>
>>> Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
>>> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
>>> Acked-by: Thierry Reding <thierry.reding@gmail.com>
>>> Acked-by: Lee Jones <lee.jones@linaro.org>
>>
>> It seems good to me:
>> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
>>
>> (Adding some people to the Cc: list).
>>
>>
>>> ---
>>> The change is based on lee-backlight/for-backlight-next
>>>
>>> Changes from v1 to v2:
>>> * rebased on top of Nicolas' commit
>>>     68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
>>>
>>> Links to previous discussions of the change:
>>> * https://patchwork.ozlabs.org/patch/483993/
>>> * https://patchwork.ozlabs.org/patch/398849/
>>>
>>>  drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
>>>  1 file changed, 9 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
>>> index eff379b..ae3c6b6 100644
>>> --- a/drivers/video/backlight/pwm_bl.c
>>> +++ b/drivers/video/backlight/pwm_bl.c
>>> @@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>>>  	}
>>>  
>>>  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
>>> -	if (IS_ERR(pb->pwm)) {
>>> -		ret = PTR_ERR(pb->pwm);
>>> -		if (ret = -EPROBE_DEFER)
>>> -			goto err_alloc;
>>> -
>>> +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
>>> +	    && !pdev->dev.of_node) {
>>>  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
>>>  		pb->legacy = true;
>>>  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
>>> -		if (IS_ERR(pb->pwm)) {
>>> -			dev_err(&pdev->dev, "unable to request legacy PWM\n");
>>> -			ret = PTR_ERR(pb->pwm);
>>> -			goto err_alloc;
>>> -		}
>>> +	}
>>> +
>>> +	if (IS_ERR(pb->pwm)) {
>>> +		ret = PTR_ERR(pb->pwm);
>>> +		if (ret != -EPROBE_DEFER)
>>> +			dev_err(&pdev->dev, "unable to request PWM\n");
>>> +		goto err_alloc;
>>>  	}
>>>  
>>>  	dev_dbg(&pdev->dev, "got pwm for backlight\n");
>>>
>>
>>
> 
> I still think it would be cleaner to do what Thierry proposed here [1].
> IMO, embedding the complexity of different error cases depending on the
> way PWM devices were defined (OF, pdata, ...) is rather risky and
> make the code even more complicated.

please correct me if I'm wrong, I suppose Thierry's change fixes
Nicolas' commit 68feaca0b13 only, and the intention of my change is to
fix an absolutely unrelated problem, see the commit message.

So, since still there is a remained chance of getting -EPROBE_DEFER from
pwm_get(), e.g. from of_pwm_get() or failed pwmchip_find_by_name() or
pwm->chip->ops->request() I don't see how Thierry's change alone may
help me to overcome the problem I'm trying to solve here.

> Best Regards,
> 
> Boris
> 
> [1]https://lkml.org/lkml/2015/10/5/319
> 
> 

--
With best wishes,
Vladimir

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Boris Brezillon]

On Mon, 12 Oct 2015 16:54:39 +0300
Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> wrote:

> Hi Boris,
> 
> On 12.10.2015 16:30, Boris Brezillon wrote:
> > Hi Vladimir,
> > 
> > On Mon, 12 Oct 2015 15:16:44 +0200
> > Nicolas Ferre <nicolas.ferre@atmel.com> wrote:
> > 
> >> Le 12/10/2015 14:29, Vladimir Zapolskiy a écrit :
> >>> Platform PWM backlight data provided by board's device tree should be
> >>> complete enough to successfully request a pwm device using pwm_get()
> >>> API. This change fixes a bug, when an arbitrary (first found) PWM is
> >>> connected to a "pwm-backlight" compatible device, when explicit PWM
> >>> device reference is not given.
> >>>
> >>> Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> >>> already describes "pwms" as a required property, instead of blind
> >>> selection of a potentially wrong PWM reject legacy PWM device
> >>> registration request, leave legacy API only for non-dt cases.
> >>>
> >>> Based on initial implementation done by Dmitry Eremin-Solenikov.
> >>>
> >>> Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
> >>> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
> >>> Acked-by: Thierry Reding <thierry.reding@gmail.com>
> >>> Acked-by: Lee Jones <lee.jones@linaro.org>
> >>
> >> It seems good to me:
> >> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
> >>
> >> (Adding some people to the Cc: list).
> >>
> >>
> >>> ---
> >>> The change is based on lee-backlight/for-backlight-next
> >>>
> >>> Changes from v1 to v2:
> >>> * rebased on top of Nicolas' commit
> >>>     68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
> >>>
> >>> Links to previous discussions of the change:
> >>> * https://patchwork.ozlabs.org/patch/483993/
> >>> * https://patchwork.ozlabs.org/patch/398849/
> >>>
> >>>  drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
> >>>  1 file changed, 9 insertions(+), 10 deletions(-)
> >>>
> >>> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> >>> index eff379b..ae3c6b6 100644
> >>> --- a/drivers/video/backlight/pwm_bl.c
> >>> +++ b/drivers/video/backlight/pwm_bl.c
> >>> @@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> >>>  	}
> >>>  
> >>>  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
> >>> -	if (IS_ERR(pb->pwm)) {
> >>> -		ret = PTR_ERR(pb->pwm);
> >>> -		if (ret == -EPROBE_DEFER)
> >>> -			goto err_alloc;
> >>> -
> >>> +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
> >>> +	    && !pdev->dev.of_node) {
> >>>  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
> >>>  		pb->legacy = true;
> >>>  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
> >>> -		if (IS_ERR(pb->pwm)) {
> >>> -			dev_err(&pdev->dev, "unable to request legacy PWM\n");
> >>> -			ret = PTR_ERR(pb->pwm);
> >>> -			goto err_alloc;
> >>> -		}
> >>> +	}
> >>> +
> >>> +	if (IS_ERR(pb->pwm)) {
> >>> +		ret = PTR_ERR(pb->pwm);
> >>> +		if (ret != -EPROBE_DEFER)
> >>> +			dev_err(&pdev->dev, "unable to request PWM\n");
> >>> +		goto err_alloc;
> >>>  	}
> >>>  
> >>>  	dev_dbg(&pdev->dev, "got pwm for backlight\n");
> >>>
> >>
> >>
> > 
> > I still think it would be cleaner to do what Thierry proposed here [1].
> > IMO, embedding the complexity of different error cases depending on the
> > way PWM devices were defined (OF, pdata, ...) is rather risky and
> > make the code even more complicated.
> 
> please correct me if I'm wrong, I suppose Thierry's change fixes
> Nicolas' commit 68feaca0b13 only, and the intention of my change is to
> fix an absolutely unrelated problem, see the commit message.
> 
> So, since still there is a remained chance of getting -EPROBE_DEFER from
> pwm_get(), e.g. from of_pwm_get() or failed pwmchip_find_by_name() or
> pwm->chip->ops->request() I don't see how Thierry's change alone may
> help me to overcome the problem I'm trying to solve here.

The only valid case where EPROBE_DEFER should be returned is when we
have a device that is not ready to be used yet (but we're sure that we
have this device declared, using either the PWM lookup table or the DT
definition in the PWM subsystem case).
Thierry's patch makes sure that EPROBE_DEFER is not returned when the
PWM device definition is not found using in the PWM lookup tables or
the DT definition, and in this case the pwm_bl code will fallback to
the legacy PWM API, which AFAICT is what you're trying to solve.

Best Regards,

Boris
-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Boris Brezillon]

On Mon, 12 Oct 2015 16:54:39 +0300
Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> wrote:

> Hi Boris,
> 
> On 12.10.2015 16:30, Boris Brezillon wrote:
> > Hi Vladimir,
> > 
> > On Mon, 12 Oct 2015 15:16:44 +0200
> > Nicolas Ferre <nicolas.ferre@atmel.com> wrote:
> > 
> >> Le 12/10/2015 14:29, Vladimir Zapolskiy a écrit :
> >>> Platform PWM backlight data provided by board's device tree should be
> >>> complete enough to successfully request a pwm device using pwm_get()
> >>> API. This change fixes a bug, when an arbitrary (first found) PWM is
> >>> connected to a "pwm-backlight" compatible device, when explicit PWM
> >>> device reference is not given.
> >>>
> >>> Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> >>> already describes "pwms" as a required property, instead of blind
> >>> selection of a potentially wrong PWM reject legacy PWM device
> >>> registration request, leave legacy API only for non-dt cases.
> >>>
> >>> Based on initial implementation done by Dmitry Eremin-Solenikov.
> >>>
> >>> Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
> >>> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
> >>> Acked-by: Thierry Reding <thierry.reding@gmail.com>
> >>> Acked-by: Lee Jones <lee.jones@linaro.org>
> >>
> >> It seems good to me:
> >> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
> >>
> >> (Adding some people to the Cc: list).
> >>
> >>
> >>> ---
> >>> The change is based on lee-backlight/for-backlight-next
> >>>
> >>> Changes from v1 to v2:
> >>> * rebased on top of Nicolas' commit
> >>>     68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
> >>>
> >>> Links to previous discussions of the change:
> >>> * https://patchwork.ozlabs.org/patch/483993/
> >>> * https://patchwork.ozlabs.org/patch/398849/
> >>>
> >>>  drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
> >>>  1 file changed, 9 insertions(+), 10 deletions(-)
> >>>
> >>> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> >>> index eff379b..ae3c6b6 100644
> >>> --- a/drivers/video/backlight/pwm_bl.c
> >>> +++ b/drivers/video/backlight/pwm_bl.c
> >>> @@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
> >>>  	}
> >>>  
> >>>  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
> >>> -	if (IS_ERR(pb->pwm)) {
> >>> -		ret = PTR_ERR(pb->pwm);
> >>> -		if (ret = -EPROBE_DEFER)
> >>> -			goto err_alloc;
> >>> -
> >>> +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
> >>> +	    && !pdev->dev.of_node) {
> >>>  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
> >>>  		pb->legacy = true;
> >>>  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
> >>> -		if (IS_ERR(pb->pwm)) {
> >>> -			dev_err(&pdev->dev, "unable to request legacy PWM\n");
> >>> -			ret = PTR_ERR(pb->pwm);
> >>> -			goto err_alloc;
> >>> -		}
> >>> +	}
> >>> +
> >>> +	if (IS_ERR(pb->pwm)) {
> >>> +		ret = PTR_ERR(pb->pwm);
> >>> +		if (ret != -EPROBE_DEFER)
> >>> +			dev_err(&pdev->dev, "unable to request PWM\n");
> >>> +		goto err_alloc;
> >>>  	}
> >>>  
> >>>  	dev_dbg(&pdev->dev, "got pwm for backlight\n");
> >>>
> >>
> >>
> > 
> > I still think it would be cleaner to do what Thierry proposed here [1].
> > IMO, embedding the complexity of different error cases depending on the
> > way PWM devices were defined (OF, pdata, ...) is rather risky and
> > make the code even more complicated.
> 
> please correct me if I'm wrong, I suppose Thierry's change fixes
> Nicolas' commit 68feaca0b13 only, and the intention of my change is to
> fix an absolutely unrelated problem, see the commit message.
> 
> So, since still there is a remained chance of getting -EPROBE_DEFER from
> pwm_get(), e.g. from of_pwm_get() or failed pwmchip_find_by_name() or
> pwm->chip->ops->request() I don't see how Thierry's change alone may
> help me to overcome the problem I'm trying to solve here.

The only valid case where EPROBE_DEFER should be returned is when we
have a device that is not ready to be used yet (but we're sure that we
have this device declared, using either the PWM lookup table or the DT
definition in the PWM subsystem case).
Thierry's patch makes sure that EPROBE_DEFER is not returned when the
PWM device definition is not found using in the PWM lookup tables or
the DT definition, and in this case the pwm_bl code will fallback to
the legacy PWM API, which AFAICT is what you're trying to solve.

Best Regards,

Boris
-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Vladimir Zapolskiy]

On 12.10.2015 17:06, Boris Brezillon wrote:
> On Mon, 12 Oct 2015 16:54:39 +0300
> Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> wrote:
> 
>> Hi Boris,
>>
>> On 12.10.2015 16:30, Boris Brezillon wrote:
>>> Hi Vladimir,
>>>
>>> On Mon, 12 Oct 2015 15:16:44 +0200
>>> Nicolas Ferre <nicolas.ferre@atmel.com> wrote:
>>>
>>>> Le 12/10/2015 14:29, Vladimir Zapolskiy a écrit :
>>>>> Platform PWM backlight data provided by board's device tree should be
>>>>> complete enough to successfully request a pwm device using pwm_get()
>>>>> API. This change fixes a bug, when an arbitrary (first found) PWM is
>>>>> connected to a "pwm-backlight" compatible device, when explicit PWM
>>>>> device reference is not given.
>>>>>
>>>>> Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
>>>>> already describes "pwms" as a required property, instead of blind
>>>>> selection of a potentially wrong PWM reject legacy PWM device
>>>>> registration request, leave legacy API only for non-dt cases.
>>>>>
>>>>> Based on initial implementation done by Dmitry Eremin-Solenikov.
>>>>>
>>>>> Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
>>>>> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
>>>>> Acked-by: Thierry Reding <thierry.reding@gmail.com>
>>>>> Acked-by: Lee Jones <lee.jones@linaro.org>
>>>>
>>>> It seems good to me:
>>>> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
>>>>
>>>> (Adding some people to the Cc: list).
>>>>
>>>>
>>>>> ---
>>>>> The change is based on lee-backlight/for-backlight-next
>>>>>
>>>>> Changes from v1 to v2:
>>>>> * rebased on top of Nicolas' commit
>>>>>     68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
>>>>>
>>>>> Links to previous discussions of the change:
>>>>> * https://patchwork.ozlabs.org/patch/483993/
>>>>> * https://patchwork.ozlabs.org/patch/398849/
>>>>>
>>>>>  drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
>>>>>  1 file changed, 9 insertions(+), 10 deletions(-)
>>>>>
>>>>> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
>>>>> index eff379b..ae3c6b6 100644
>>>>> --- a/drivers/video/backlight/pwm_bl.c
>>>>> +++ b/drivers/video/backlight/pwm_bl.c
>>>>> @@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>>>>>  	}
>>>>>  
>>>>>  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
>>>>> -	if (IS_ERR(pb->pwm)) {
>>>>> -		ret = PTR_ERR(pb->pwm);
>>>>> -		if (ret == -EPROBE_DEFER)
>>>>> -			goto err_alloc;
>>>>> -
>>>>> +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
>>>>> +	    && !pdev->dev.of_node) {
>>>>>  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
>>>>>  		pb->legacy = true;
>>>>>  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
>>>>> -		if (IS_ERR(pb->pwm)) {
>>>>> -			dev_err(&pdev->dev, "unable to request legacy PWM\n");
>>>>> -			ret = PTR_ERR(pb->pwm);
>>>>> -			goto err_alloc;
>>>>> -		}
>>>>> +	}
>>>>> +
>>>>> +	if (IS_ERR(pb->pwm)) {
>>>>> +		ret = PTR_ERR(pb->pwm);
>>>>> +		if (ret != -EPROBE_DEFER)
>>>>> +			dev_err(&pdev->dev, "unable to request PWM\n");
>>>>> +		goto err_alloc;
>>>>>  	}
>>>>>  
>>>>>  	dev_dbg(&pdev->dev, "got pwm for backlight\n");
>>>>>
>>>>
>>>>
>>>
>>> I still think it would be cleaner to do what Thierry proposed here [1].
>>> IMO, embedding the complexity of different error cases depending on the
>>> way PWM devices were defined (OF, pdata, ...) is rather risky and
>>> make the code even more complicated.
>>
>> please correct me if I'm wrong, I suppose Thierry's change fixes
>> Nicolas' commit 68feaca0b13 only, and the intention of my change is to
>> fix an absolutely unrelated problem, see the commit message.
>>
>> So, since still there is a remained chance of getting -EPROBE_DEFER from
>> pwm_get(), e.g. from of_pwm_get() or failed pwmchip_find_by_name() or
>> pwm->chip->ops->request() I don't see how Thierry's change alone may
>> help me to overcome the problem I'm trying to solve here.
> 
> The only valid case where EPROBE_DEFER should be returned is when we
> have a device that is not ready to be used yet (but we're sure that we
> have this device declared, using either the PWM lookup table or the DT
> definition in the PWM subsystem case).

That's fine, and it is reflected in my change.

> Thierry's patch makes sure that EPROBE_DEFER is not returned when the
> PWM device definition is not found using in the PWM lookup tables or
> the DT definition,

This is okay, but I'm interested in proper handling of cases other than
EPROBE_DEFER. EPROBE_DEFER and the related issues are on your balance
and I'm attempting to avoid interfering with it here :)

> and in this case the pwm_bl code will fallback to
> the legacy PWM API, which AFAICT is what you're trying to solve.

Fallback must happen exclusively under (IS_ERR(pb->pwm) &&
PTR_ERR(pb->pwm) != -EPROBE_DEFER && !pdev->dev.of_node) condition IMHO.

Before EPROBE_DEFER appeared on the scene the condition was
(IS_ERR(pb->pwm) && !pdev->dev.of_node).

So, the question is if my change requires any updates or not from your
point of view.

--
With best wishes,
Vladimir

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Vladimir Zapolskiy]

On 12.10.2015 17:06, Boris Brezillon wrote:
> On Mon, 12 Oct 2015 16:54:39 +0300
> Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> wrote:
> 
>> Hi Boris,
>>
>> On 12.10.2015 16:30, Boris Brezillon wrote:
>>> Hi Vladimir,
>>>
>>> On Mon, 12 Oct 2015 15:16:44 +0200
>>> Nicolas Ferre <nicolas.ferre@atmel.com> wrote:
>>>
>>>> Le 12/10/2015 14:29, Vladimir Zapolskiy a écrit :
>>>>> Platform PWM backlight data provided by board's device tree should be
>>>>> complete enough to successfully request a pwm device using pwm_get()
>>>>> API. This change fixes a bug, when an arbitrary (first found) PWM is
>>>>> connected to a "pwm-backlight" compatible device, when explicit PWM
>>>>> device reference is not given.
>>>>>
>>>>> Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
>>>>> already describes "pwms" as a required property, instead of blind
>>>>> selection of a potentially wrong PWM reject legacy PWM device
>>>>> registration request, leave legacy API only for non-dt cases.
>>>>>
>>>>> Based on initial implementation done by Dmitry Eremin-Solenikov.
>>>>>
>>>>> Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
>>>>> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
>>>>> Acked-by: Thierry Reding <thierry.reding@gmail.com>
>>>>> Acked-by: Lee Jones <lee.jones@linaro.org>
>>>>
>>>> It seems good to me:
>>>> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
>>>>
>>>> (Adding some people to the Cc: list).
>>>>
>>>>
>>>>> ---
>>>>> The change is based on lee-backlight/for-backlight-next
>>>>>
>>>>> Changes from v1 to v2:
>>>>> * rebased on top of Nicolas' commit
>>>>>     68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
>>>>>
>>>>> Links to previous discussions of the change:
>>>>> * https://patchwork.ozlabs.org/patch/483993/
>>>>> * https://patchwork.ozlabs.org/patch/398849/
>>>>>
>>>>>  drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
>>>>>  1 file changed, 9 insertions(+), 10 deletions(-)
>>>>>
>>>>> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
>>>>> index eff379b..ae3c6b6 100644
>>>>> --- a/drivers/video/backlight/pwm_bl.c
>>>>> +++ b/drivers/video/backlight/pwm_bl.c
>>>>> @@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>>>>>  	}
>>>>>  
>>>>>  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
>>>>> -	if (IS_ERR(pb->pwm)) {
>>>>> -		ret = PTR_ERR(pb->pwm);
>>>>> -		if (ret = -EPROBE_DEFER)
>>>>> -			goto err_alloc;
>>>>> -
>>>>> +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
>>>>> +	    && !pdev->dev.of_node) {
>>>>>  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
>>>>>  		pb->legacy = true;
>>>>>  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
>>>>> -		if (IS_ERR(pb->pwm)) {
>>>>> -			dev_err(&pdev->dev, "unable to request legacy PWM\n");
>>>>> -			ret = PTR_ERR(pb->pwm);
>>>>> -			goto err_alloc;
>>>>> -		}
>>>>> +	}
>>>>> +
>>>>> +	if (IS_ERR(pb->pwm)) {
>>>>> +		ret = PTR_ERR(pb->pwm);
>>>>> +		if (ret != -EPROBE_DEFER)
>>>>> +			dev_err(&pdev->dev, "unable to request PWM\n");
>>>>> +		goto err_alloc;
>>>>>  	}
>>>>>  
>>>>>  	dev_dbg(&pdev->dev, "got pwm for backlight\n");
>>>>>
>>>>
>>>>
>>>
>>> I still think it would be cleaner to do what Thierry proposed here [1].
>>> IMO, embedding the complexity of different error cases depending on the
>>> way PWM devices were defined (OF, pdata, ...) is rather risky and
>>> make the code even more complicated.
>>
>> please correct me if I'm wrong, I suppose Thierry's change fixes
>> Nicolas' commit 68feaca0b13 only, and the intention of my change is to
>> fix an absolutely unrelated problem, see the commit message.
>>
>> So, since still there is a remained chance of getting -EPROBE_DEFER from
>> pwm_get(), e.g. from of_pwm_get() or failed pwmchip_find_by_name() or
>> pwm->chip->ops->request() I don't see how Thierry's change alone may
>> help me to overcome the problem I'm trying to solve here.
> 
> The only valid case where EPROBE_DEFER should be returned is when we
> have a device that is not ready to be used yet (but we're sure that we
> have this device declared, using either the PWM lookup table or the DT
> definition in the PWM subsystem case).

That's fine, and it is reflected in my change.

> Thierry's patch makes sure that EPROBE_DEFER is not returned when the
> PWM device definition is not found using in the PWM lookup tables or
> the DT definition,

This is okay, but I'm interested in proper handling of cases other than
EPROBE_DEFER. EPROBE_DEFER and the related issues are on your balance
and I'm attempting to avoid interfering with it here :)

> and in this case the pwm_bl code will fallback to
> the legacy PWM API, which AFAICT is what you're trying to solve.

Fallback must happen exclusively under (IS_ERR(pb->pwm) &&
PTR_ERR(pb->pwm) != -EPROBE_DEFER && !pdev->dev.of_node) condition IMHO.

Before EPROBE_DEFER appeared on the scene the condition was
(IS_ERR(pb->pwm) && !pdev->dev.of_node).

So, the question is if my change requires any updates or not from your
point of view.

--
With best wishes,
Vladimir

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Boris Brezillon]

On Mon, 12 Oct 2015 17:19:35 +0300
Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> wrote:
> 
> > Thierry's patch makes sure that EPROBE_DEFER is not returned when the
> > PWM device definition is not found using in the PWM lookup tables or
> > the DT definition,
> 
> This is okay, but I'm interested in proper handling of cases other than
> EPROBE_DEFER. EPROBE_DEFER and the related issues are on your balance
> and I'm attempting to avoid interfering with it here :)

I keep thinking we should fix all platforms using the ->pwm_id pdata
field to attach a PWM device to a PWM backlight instead of trying to
guess when falling back to the legacy API is acceptable...

> 
> > and in this case the pwm_bl code will fallback to
> > the legacy PWM API, which AFAICT is what you're trying to solve.
> 
> Fallback must happen exclusively under (IS_ERR(pb->pwm) &&
> PTR_ERR(pb->pwm) != -EPROBE_DEFER && !pdev->dev.of_node) condition IMHO.
> 
> Before EPROBE_DEFER appeared on the scene the condition was
> (IS_ERR(pb->pwm) && !pdev->dev.of_node).
> 
> So, the question is if my change requires any updates or not from your
> point of view.

... but from a functional point of view your patch seems correct.

Best Regards,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Boris Brezillon]

On Mon, 12 Oct 2015 17:19:35 +0300
Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> wrote:
> 
> > Thierry's patch makes sure that EPROBE_DEFER is not returned when the
> > PWM device definition is not found using in the PWM lookup tables or
> > the DT definition,
> 
> This is okay, but I'm interested in proper handling of cases other than
> EPROBE_DEFER. EPROBE_DEFER and the related issues are on your balance
> and I'm attempting to avoid interfering with it here :)

I keep thinking we should fix all platforms using the ->pwm_id pdata
field to attach a PWM device to a PWM backlight instead of trying to
guess when falling back to the legacy API is acceptable...

> 
> > and in this case the pwm_bl code will fallback to
> > the legacy PWM API, which AFAICT is what you're trying to solve.
> 
> Fallback must happen exclusively under (IS_ERR(pb->pwm) &&
> PTR_ERR(pb->pwm) != -EPROBE_DEFER && !pdev->dev.of_node) condition IMHO.
> 
> Before EPROBE_DEFER appeared on the scene the condition was
> (IS_ERR(pb->pwm) && !pdev->dev.of_node).
> 
> So, the question is if my change requires any updates or not from your
> point of view.

... but from a functional point of view your patch seems correct.

Best Regards,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Vladimir Zapolskiy]

On 12.10.2015 18:19, Boris Brezillon wrote:
> On Mon, 12 Oct 2015 17:19:35 +0300
> Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> wrote:
>>
>>> Thierry's patch makes sure that EPROBE_DEFER is not returned when the
>>> PWM device definition is not found using in the PWM lookup tables or
>>> the DT definition,
>>
>> This is okay, but I'm interested in proper handling of cases other than
>> EPROBE_DEFER. EPROBE_DEFER and the related issues are on your balance
>> and I'm attempting to avoid interfering with it here :)
> 
> I keep thinking we should fix all platforms using the ->pwm_id pdata
> field to attach a PWM device to a PWM backlight instead of trying to
> guess when falling back to the legacy API is acceptable...
> 
>>
>>> and in this case the pwm_bl code will fallback to
>>> the legacy PWM API, which AFAICT is what you're trying to solve.
>>
>> Fallback must happen exclusively under (IS_ERR(pb->pwm) &&
>> PTR_ERR(pb->pwm) != -EPROBE_DEFER && !pdev->dev.of_node) condition IMHO.
>>
>> Before EPROBE_DEFER appeared on the scene the condition was
>> (IS_ERR(pb->pwm) && !pdev->dev.of_node).
>>
>> So, the question is if my change requires any updates or not from your
>> point of view.
> 
> ... but from a functional point of view your patch seems correct.

Sounds good, thank you for review.


Robert,

because you found a regression in the related area of code on a
platform, which uses legacy PWM API, could you please confirm that three
patches applied in a row don't break anything for you, the changes are:

* Nicolas' 68feaca0b1 ("backlight: pwm: Handle EPROBE_DEFER while
requesting the PWM")
* Thierry' https://lkml.org/lkml/2015/10/5/319
* and this one is the last in the series:
http://thread.gmane.org/gmane.linux.pwm/2813

--
With best wishes,
Vladimir

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Vladimir Zapolskiy]

On 12.10.2015 18:19, Boris Brezillon wrote:
> On Mon, 12 Oct 2015 17:19:35 +0300
> Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> wrote:
>>
>>> Thierry's patch makes sure that EPROBE_DEFER is not returned when the
>>> PWM device definition is not found using in the PWM lookup tables or
>>> the DT definition,
>>
>> This is okay, but I'm interested in proper handling of cases other than
>> EPROBE_DEFER. EPROBE_DEFER and the related issues are on your balance
>> and I'm attempting to avoid interfering with it here :)
> 
> I keep thinking we should fix all platforms using the ->pwm_id pdata
> field to attach a PWM device to a PWM backlight instead of trying to
> guess when falling back to the legacy API is acceptable...
> 
>>
>>> and in this case the pwm_bl code will fallback to
>>> the legacy PWM API, which AFAICT is what you're trying to solve.
>>
>> Fallback must happen exclusively under (IS_ERR(pb->pwm) &&
>> PTR_ERR(pb->pwm) != -EPROBE_DEFER && !pdev->dev.of_node) condition IMHO.
>>
>> Before EPROBE_DEFER appeared on the scene the condition was
>> (IS_ERR(pb->pwm) && !pdev->dev.of_node).
>>
>> So, the question is if my change requires any updates or not from your
>> point of view.
> 
> ... but from a functional point of view your patch seems correct.

Sounds good, thank you for review.


Robert,

because you found a regression in the related area of code on a
platform, which uses legacy PWM API, could you please confirm that three
patches applied in a row don't break anything for you, the changes are:

* Nicolas' 68feaca0b1 ("backlight: pwm: Handle EPROBE_DEFER while
requesting the PWM")
* Thierry' https://lkml.org/lkml/2015/10/5/319
* and this one is the last in the series:
http://thread.gmane.org/gmane.linux.pwm/2813

--
With best wishes,
Vladimir

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Robert Jarzmik]

Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> writes:

> Sounds good, thank you for review.
>
>
> Robert,
>
> because you found a regression in the related area of code on a
> platform, which uses legacy PWM API, could you please confirm that three
> patches applied in a row don't break anything for you, the changes are:
>
> * Nicolas' 68feaca0b1 ("backlight: pwm: Handle EPROBE_DEFER while
> requesting the PWM")
> * Thierry' https://lkml.org/lkml/2015/10/5/319
> * and this one is the last in the series:
> http://thread.gmane.org/gmane.linux.pwm/2813
>
> --
> With best wishes,
> Vladimir
Of course, on my way.

Cheers.

-- 
Robert

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Robert Jarzmik]

Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> writes:

> Sounds good, thank you for review.
>
>
> Robert,
>
> because you found a regression in the related area of code on a
> platform, which uses legacy PWM API, could you please confirm that three
> patches applied in a row don't break anything for you, the changes are:
>
> * Nicolas' 68feaca0b1 ("backlight: pwm: Handle EPROBE_DEFER while
> requesting the PWM")
> * Thierry' https://lkml.org/lkml/2015/10/5/319
> * and this one is the last in the series:
> http://thread.gmane.org/gmane.linux.pwm/2813
>
> --
> With best wishes,
> Vladimir
Of course, on my way.

Cheers.

-- 
Robert

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Lee Jones]

On Mon, 12 Oct 2015, Vladimir Zapolskiy wrote:

> On 12.10.2015 18:19, Boris Brezillon wrote:
> > On Mon, 12 Oct 2015 17:19:35 +0300
> > Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> wrote:
> >>
> >>> Thierry's patch makes sure that EPROBE_DEFER is not returned when the
> >>> PWM device definition is not found using in the PWM lookup tables or
> >>> the DT definition,
> >>
> >> This is okay, but I'm interested in proper handling of cases other than
> >> EPROBE_DEFER. EPROBE_DEFER and the related issues are on your balance
> >> and I'm attempting to avoid interfering with it here :)
> > 
> > I keep thinking we should fix all platforms using the ->pwm_id pdata
> > field to attach a PWM device to a PWM backlight instead of trying to
> > guess when falling back to the legacy API is acceptable...
> > 
> >>
> >>> and in this case the pwm_bl code will fallback to
> >>> the legacy PWM API, which AFAICT is what you're trying to solve.
> >>
> >> Fallback must happen exclusively under (IS_ERR(pb->pwm) &&
> >> PTR_ERR(pb->pwm) != -EPROBE_DEFER && !pdev->dev.of_node) condition IMHO.
> >>
> >> Before EPROBE_DEFER appeared on the scene the condition was
> >> (IS_ERR(pb->pwm) && !pdev->dev.of_node).
> >>
> >> So, the question is if my change requires any updates or not from your
> >> point of view.
> > 
> > ... but from a functional point of view your patch seems correct.
> 
> Sounds good, thank you for review.

So should I take this patch, or not?

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

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Lee Jones]

On Mon, 12 Oct 2015, Vladimir Zapolskiy wrote:

> On 12.10.2015 18:19, Boris Brezillon wrote:
> > On Mon, 12 Oct 2015 17:19:35 +0300
> > Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> wrote:
> >>
> >>> Thierry's patch makes sure that EPROBE_DEFER is not returned when the
> >>> PWM device definition is not found using in the PWM lookup tables or
> >>> the DT definition,
> >>
> >> This is okay, but I'm interested in proper handling of cases other than
> >> EPROBE_DEFER. EPROBE_DEFER and the related issues are on your balance
> >> and I'm attempting to avoid interfering with it here :)
> > 
> > I keep thinking we should fix all platforms using the ->pwm_id pdata
> > field to attach a PWM device to a PWM backlight instead of trying to
> > guess when falling back to the legacy API is acceptable...
> > 
> >>
> >>> and in this case the pwm_bl code will fallback to
> >>> the legacy PWM API, which AFAICT is what you're trying to solve.
> >>
> >> Fallback must happen exclusively under (IS_ERR(pb->pwm) &&
> >> PTR_ERR(pb->pwm) != -EPROBE_DEFER && !pdev->dev.of_node) condition IMHO.
> >>
> >> Before EPROBE_DEFER appeared on the scene the condition was
> >> (IS_ERR(pb->pwm) && !pdev->dev.of_node).
> >>
> >> So, the question is if my change requires any updates or not from your
> >> point of view.
> > 
> > ... but from a functional point of view your patch seems correct.
> 
> Sounds good, thank you for review.

So should I take this patch, or not?

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

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Vladimir Zapolskiy]

Hi Lee,

Lee,On 13.10.2015 10:29, Lee Jones wrote:
> On Mon, 12 Oct 2015, Vladimir Zapolskiy wrote:
> 
>> On 12.10.2015 18:19, Boris Brezillon wrote:
>>> On Mon, 12 Oct 2015 17:19:35 +0300
>>> Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> wrote:
>>>>
>>>>> Thierry's patch makes sure that EPROBE_DEFER is not returned when the
>>>>> PWM device definition is not found using in the PWM lookup tables or
>>>>> the DT definition,
>>>>
>>>> This is okay, but I'm interested in proper handling of cases other than
>>>> EPROBE_DEFER. EPROBE_DEFER and the related issues are on your balance
>>>> and I'm attempting to avoid interfering with it here :)
>>>
>>> I keep thinking we should fix all platforms using the ->pwm_id pdata
>>> field to attach a PWM device to a PWM backlight instead of trying to
>>> guess when falling back to the legacy API is acceptable...
>>>
>>>>
>>>>> and in this case the pwm_bl code will fallback to
>>>>> the legacy PWM API, which AFAICT is what you're trying to solve.
>>>>
>>>> Fallback must happen exclusively under (IS_ERR(pb->pwm) &&
>>>> PTR_ERR(pb->pwm) != -EPROBE_DEFER && !pdev->dev.of_node) condition IMHO.
>>>>
>>>> Before EPROBE_DEFER appeared on the scene the condition was
>>>> (IS_ERR(pb->pwm) && !pdev->dev.of_node).
>>>>
>>>> So, the question is if my change requires any updates or not from your
>>>> point of view.
>>>
>>> ... but from a functional point of view your patch seems correct.
>>
>> Sounds good, thank you for review.
> 
> So should I take this patch, or not?
> 

Robert's testing shows no regression, please apply this change on top of
Nicolas' one.

--
With best wishes,
Vladimir

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Vladimir Zapolskiy]

Hi Lee,

Lee,On 13.10.2015 10:29, Lee Jones wrote:
> On Mon, 12 Oct 2015, Vladimir Zapolskiy wrote:
> 
>> On 12.10.2015 18:19, Boris Brezillon wrote:
>>> On Mon, 12 Oct 2015 17:19:35 +0300
>>> Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> wrote:
>>>>
>>>>> Thierry's patch makes sure that EPROBE_DEFER is not returned when the
>>>>> PWM device definition is not found using in the PWM lookup tables or
>>>>> the DT definition,
>>>>
>>>> This is okay, but I'm interested in proper handling of cases other than
>>>> EPROBE_DEFER. EPROBE_DEFER and the related issues are on your balance
>>>> and I'm attempting to avoid interfering with it here :)
>>>
>>> I keep thinking we should fix all platforms using the ->pwm_id pdata
>>> field to attach a PWM device to a PWM backlight instead of trying to
>>> guess when falling back to the legacy API is acceptable...
>>>
>>>>
>>>>> and in this case the pwm_bl code will fallback to
>>>>> the legacy PWM API, which AFAICT is what you're trying to solve.
>>>>
>>>> Fallback must happen exclusively under (IS_ERR(pb->pwm) &&
>>>> PTR_ERR(pb->pwm) != -EPROBE_DEFER && !pdev->dev.of_node) condition IMHO.
>>>>
>>>> Before EPROBE_DEFER appeared on the scene the condition was
>>>> (IS_ERR(pb->pwm) && !pdev->dev.of_node).
>>>>
>>>> So, the question is if my change requires any updates or not from your
>>>> point of view.
>>>
>>> ... but from a functional point of view your patch seems correct.
>>
>> Sounds good, thank you for review.
> 
> So should I take this patch, or not?
> 

Robert's testing shows no regression, please apply this change on top of
Nicolas' one.

--
With best wishes,
Vladimir

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Robert Jarzmik]

Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> writes:

> Robert,
>
> because you found a regression in the related area of code on a
> platform, which uses legacy PWM API, could you please confirm that three
> patches applied in a row don't break anything for you, the changes are:
>
> * Nicolas' 68feaca0b1 ("backlight: pwm: Handle EPROBE_DEFER while
> requesting the PWM")
> * Thierry' https://lkml.org/lkml/2015/10/5/319
> * and this one is the last in the series:
> http://thread.gmane.org/gmane.linux.pwm/2813
I confirm, my backlight works again with it :
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>

Cheers.

-- 
Robert

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Robert Jarzmik]

Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com> writes:

> Robert,
>
> because you found a regression in the related area of code on a
> platform, which uses legacy PWM API, could you please confirm that three
> patches applied in a row don't break anything for you, the changes are:
>
> * Nicolas' 68feaca0b1 ("backlight: pwm: Handle EPROBE_DEFER while
> requesting the PWM")
> * Thierry' https://lkml.org/lkml/2015/10/5/319
> * and this one is the last in the series:
> http://thread.gmane.org/gmane.linux.pwm/2813
I confirm, my backlight works again with it :
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>

Cheers.

-- 
Robert

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Lee Jones]

On Mon, 12 Oct 2015, Vladimir Zapolskiy wrote:

> Platform PWM backlight data provided by board's device tree should be
> complete enough to successfully request a pwm device using pwm_get()
> API. This change fixes a bug, when an arbitrary (first found) PWM is
> connected to a "pwm-backlight" compatible device, when explicit PWM
> device reference is not given.
> 
> Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> already describes "pwms" as a required property, instead of blind
> selection of a potentially wrong PWM reject legacy PWM device
> registration request, leave legacy API only for non-dt cases.
> 
> Based on initial implementation done by Dmitry Eremin-Solenikov.
> 
> Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
> Acked-by: Thierry Reding <thierry.reding@gmail.com>
> Acked-by: Lee Jones <lee.jones@linaro.org>
> ---
> The change is based on lee-backlight/for-backlight-next
> 
> Changes from v1 to v2:
> * rebased on top of Nicolas' commit
>     68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
> 
> Links to previous discussions of the change:
> * https://patchwork.ozlabs.org/patch/483993/
> * https://patchwork.ozlabs.org/patch/398849/
> 
>  drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
>  1 file changed, 9 insertions(+), 10 deletions(-)

Applied, thanks.

> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index eff379b..ae3c6b6 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  	}
>  
>  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
> -	if (IS_ERR(pb->pwm)) {
> -		ret = PTR_ERR(pb->pwm);
> -		if (ret == -EPROBE_DEFER)
> -			goto err_alloc;
> -
> +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
> +	    && !pdev->dev.of_node) {
>  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
>  		pb->legacy = true;
>  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
> -		if (IS_ERR(pb->pwm)) {
> -			dev_err(&pdev->dev, "unable to request legacy PWM\n");
> -			ret = PTR_ERR(pb->pwm);
> -			goto err_alloc;
> -		}
> +	}
> +
> +	if (IS_ERR(pb->pwm)) {
> +		ret = PTR_ERR(pb->pwm);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(&pdev->dev, "unable to request PWM\n");
> +		goto err_alloc;
>  	}
>  
>  	dev_dbg(&pdev->dev, "got pwm for backlight\n");

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

Re: [PATCH v2] backlight: pwm: reject legacy pwm request for device defined in dt

[Lee Jones]

On Mon, 12 Oct 2015, Vladimir Zapolskiy wrote:

> Platform PWM backlight data provided by board's device tree should be
> complete enough to successfully request a pwm device using pwm_get()
> API. This change fixes a bug, when an arbitrary (first found) PWM is
> connected to a "pwm-backlight" compatible device, when explicit PWM
> device reference is not given.
> 
> Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> already describes "pwms" as a required property, instead of blind
> selection of a potentially wrong PWM reject legacy PWM device
> registration request, leave legacy API only for non-dt cases.
> 
> Based on initial implementation done by Dmitry Eremin-Solenikov.
> 
> Reported-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
> Acked-by: Thierry Reding <thierry.reding@gmail.com>
> Acked-by: Lee Jones <lee.jones@linaro.org>
> ---
> The change is based on lee-backlight/for-backlight-next
> 
> Changes from v1 to v2:
> * rebased on top of Nicolas' commit
>     68feaca0b13 ("backlight: pwm: Handle EPROBE_DEFER while requesting the PWM")
> 
> Links to previous discussions of the change:
> * https://patchwork.ozlabs.org/patch/483993/
> * https://patchwork.ozlabs.org/patch/398849/
> 
>  drivers/video/backlight/pwm_bl.c | 19 +++++++++----------
>  1 file changed, 9 insertions(+), 10 deletions(-)

Applied, thanks.

> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index eff379b..ae3c6b6 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -271,19 +271,18 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  	}
>  
>  	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
> -	if (IS_ERR(pb->pwm)) {
> -		ret = PTR_ERR(pb->pwm);
> -		if (ret = -EPROBE_DEFER)
> -			goto err_alloc;
> -
> +	if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER
> +	    && !pdev->dev.of_node) {
>  		dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");
>  		pb->legacy = true;
>  		pb->pwm = pwm_request(data->pwm_id, "pwm-backlight");
> -		if (IS_ERR(pb->pwm)) {
> -			dev_err(&pdev->dev, "unable to request legacy PWM\n");
> -			ret = PTR_ERR(pb->pwm);
> -			goto err_alloc;
> -		}
> +	}
> +
> +	if (IS_ERR(pb->pwm)) {
> +		ret = PTR_ERR(pb->pwm);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(&pdev->dev, "unable to request PWM\n");
> +		goto err_alloc;
>  	}
>  
>  	dev_dbg(&pdev->dev, "got pwm for backlight\n");

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