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Groups > linux.kernel > #1402278 > unrolled thread

[PATCH] pwm: Fill pwm->args before calling pwm_request_from_chip()

Started byBoris Brezillon <boris.brezillon@free-electrons.com>
First post2016-05-17 12:40 +0200
Last post2016-05-17 13:20 +0200
Articles 4 — 2 participants

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  [PATCH] pwm: Fill pwm->args before calling pwm_request_from_chip() Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-05-17 12:40 +0200
    [PATCH] pwm: Fill pwm->args before calling pwm_request_from_chip() Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-05-17 12:40 +0200
      Re: [PATCH] pwm: Fill pwm->args before calling  pwm_request_from_chip() Thierry Reding <thierry.reding@gmail.com> - 2016-05-17 13:10 +0200
        Re: [PATCH] pwm: Fill pwm->args before calling  pwm_request_from_chip() Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-05-17 13:20 +0200

#1402278 — [PATCH] pwm: Fill pwm->args before calling pwm_request_from_chip()

FromBoris Brezillon <boris.brezillon@free-electrons.com>
Date2016-05-17 12:40 +0200
Subject[PATCH] pwm: Fill pwm->args before calling pwm_request_from_chip()
Message-ID<rzKzT-3om-5@gated-at.bofh.it>
Commit e39c0df1be5a ("pwm: Introduce the pwm_args concept"), moved the
period and polarity initialization steps into pwm_request_device() (called
by pwm_request_from_chip()) based on the pwm->args information.
Make sure we fill pwm->args fields before calling pwm_request_from_chip().

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reported-by: Mika Penttilä <mika.penttila@nextfour.com>
Fixes: e39c0df1be5a ("pwm: Introduce the pwm_args concept")
---
Mika,

Can you test after applying this patch and let me know if it fixes your
bug.

Thanks,

Boris

 drivers/pwm/core.c    | 12 ++++++------
 drivers/pwm/pwm-pxa.c |  4 ++--
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 427142d..3d2eeaa 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -143,10 +143,6 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
 	if (args->args[0] >= pc->npwm)
 		return ERR_PTR(-EINVAL);
 
-	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
-	if (IS_ERR(pwm))
-		return pwm;
-
 	pwm->args.period = args->args[1];
 
 	if (args->args[2] & PWM_POLARITY_INVERTED)
@@ -154,6 +150,10 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
 	else
 		pwm->args.polarity = PWM_POLARITY_NORMAL;
 
+	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
+	if (IS_ERR(pwm))
+		return pwm;
+
 	return pwm;
 }
 EXPORT_SYMBOL_GPL(of_pwm_xlate_with_flags);
@@ -169,12 +169,12 @@ of_pwm_simple_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
 	if (args->args[0] >= pc->npwm)
 		return ERR_PTR(-EINVAL);
 
+	pwm->args.period = args->args[1];
+
 	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
 	if (IS_ERR(pwm))
 		return pwm;
 
-	pwm->args.period = args->args[1];
-
 	return pwm;
 }
 
diff --git a/drivers/pwm/pwm-pxa.c b/drivers/pwm/pwm-pxa.c
index 58b709f..c33bd42 100644
--- a/drivers/pwm/pwm-pxa.c
+++ b/drivers/pwm/pwm-pxa.c
@@ -156,12 +156,12 @@ pxa_pwm_of_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
 {
 	struct pwm_device *pwm;
 
+	pwm->args.period = args->args[0];
+
 	pwm = pwm_request_from_chip(pc, 0, NULL);
 	if (IS_ERR(pwm))
 		return pwm;
 
-	pwm->args.period = args->args[0];
-
 	return pwm;
 }
 
-- 
2.7.4

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#1402279

FromBoris Brezillon <boris.brezillon@free-electrons.com>
Date2016-05-17 12:40 +0200
Message-ID<rzKzT-3om-9@gated-at.bofh.it>
In reply to#1402278
Commit e39c0df1be5a ("pwm: Introduce the pwm_args concept"), moved the
period and polarity initialization steps into pwm_request_device() (called
by pwm_request_from_chip()) based on the pwm->args information.
Make sure we fill pwm->args fields before calling pwm_request_from_chip().

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reported-by: Mika Penttilä <mika.penttila@nextfour.com>
Fixes: e39c0df1be5a ("pwm: Introduce the pwm_args concept")
---
Mika,

Can you test after applying this patch and let me know if it fixes your
bug.

Thanks,

Boris

 drivers/pwm/core.c    | 12 ++++++------
 drivers/pwm/pwm-pxa.c |  4 ++--
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 427142d..3d2eeaa 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -143,10 +143,6 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
 	if (args->args[0] >= pc->npwm)
 		return ERR_PTR(-EINVAL);
 
-	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
-	if (IS_ERR(pwm))
-		return pwm;
-
 	pwm->args.period = args->args[1];
 
 	if (args->args[2] & PWM_POLARITY_INVERTED)
@@ -154,6 +150,10 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
 	else
 		pwm->args.polarity = PWM_POLARITY_NORMAL;
 
+	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
+	if (IS_ERR(pwm))
+		return pwm;
+
 	return pwm;
 }
 EXPORT_SYMBOL_GPL(of_pwm_xlate_with_flags);
@@ -169,12 +169,12 @@ of_pwm_simple_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
 	if (args->args[0] >= pc->npwm)
 		return ERR_PTR(-EINVAL);
 
+	pwm->args.period = args->args[1];
+
 	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
 	if (IS_ERR(pwm))
 		return pwm;
 
-	pwm->args.period = args->args[1];
-
 	return pwm;
 }
 
diff --git a/drivers/pwm/pwm-pxa.c b/drivers/pwm/pwm-pxa.c
index 58b709f..c33bd42 100644
--- a/drivers/pwm/pwm-pxa.c
+++ b/drivers/pwm/pwm-pxa.c
@@ -156,12 +156,12 @@ pxa_pwm_of_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
 {
 	struct pwm_device *pwm;
 
+	pwm->args.period = args->args[0];
+
 	pwm = pwm_request_from_chip(pc, 0, NULL);
 	if (IS_ERR(pwm))
 		return pwm;
 
-	pwm->args.period = args->args[0];
-
 	return pwm;
 }
 
-- 
2.7.4

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#1402291 — Re: [PATCH] pwm: Fill pwm->args before calling pwm_request_from_chip()

FromThierry Reding <thierry.reding@gmail.com>
Date2016-05-17 13:10 +0200
SubjectRe: [PATCH] pwm: Fill pwm->args before calling pwm_request_from_chip()
Message-ID<rzL2W-3NJ-25@gated-at.bofh.it>
In reply to#1402279

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

On Tue, May 17, 2016 at 12:35:33PM +0200, Boris Brezillon wrote:
[...]
> diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> index 427142d..3d2eeaa 100644
> --- a/drivers/pwm/core.c
> +++ b/drivers/pwm/core.c
> @@ -143,10 +143,6 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
>  	if (args->args[0] >= pc->npwm)
>  		return ERR_PTR(-EINVAL);
>  
> -	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
> -	if (IS_ERR(pwm))
> -		return pwm;
> -
>  	pwm->args.period = args->args[1];
>  
>  	if (args->args[2] & PWM_POLARITY_INVERTED)
> @@ -154,6 +150,10 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
>  	else
>  		pwm->args.polarity = PWM_POLARITY_NORMAL;
>  
> +	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
> +	if (IS_ERR(pwm))
> +		return pwm;
> +

Can't do that, because now you're dereferencing an uninitialized
pointer.

>  	return pwm;
>  }
>  EXPORT_SYMBOL_GPL(of_pwm_xlate_with_flags);
> @@ -169,12 +169,12 @@ of_pwm_simple_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
>  	if (args->args[0] >= pc->npwm)
>  		return ERR_PTR(-EINVAL);
>  
> +	pwm->args.period = args->args[1];

Same here.

> diff --git a/drivers/pwm/pwm-pxa.c b/drivers/pwm/pwm-pxa.c
> index 58b709f..c33bd42 100644
> --- a/drivers/pwm/pwm-pxa.c
> +++ b/drivers/pwm/pwm-pxa.c
> @@ -156,12 +156,12 @@ pxa_pwm_of_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
>  {
>  	struct pwm_device *pwm;
>  
> +	pwm->args.period = args->args[0];

And here.

Thierry

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#1402295 — Re: [PATCH] pwm: Fill pwm->args before calling pwm_request_from_chip()

FromBoris Brezillon <boris.brezillon@free-electrons.com>
Date2016-05-17 13:20 +0200
SubjectRe: [PATCH] pwm: Fill pwm->args before calling pwm_request_from_chip()
Message-ID<rzLcC-3QQ-23@gated-at.bofh.it>
In reply to#1402291
On Tue, 17 May 2016 13:04:38 +0200
Thierry Reding <thierry.reding@gmail.com> wrote:

> On Tue, May 17, 2016 at 12:35:33PM +0200, Boris Brezillon wrote:
> [...]
> > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> > index 427142d..3d2eeaa 100644
> > --- a/drivers/pwm/core.c
> > +++ b/drivers/pwm/core.c
> > @@ -143,10 +143,6 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
> >  	if (args->args[0] >= pc->npwm)
> >  		return ERR_PTR(-EINVAL);
> >  
> > -	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
> > -	if (IS_ERR(pwm))
> > -		return pwm;
> > -
> >  	pwm->args.period = args->args[1];
> >  
> >  	if (args->args[2] & PWM_POLARITY_INVERTED)
> > @@ -154,6 +150,10 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
> >  	else
> >  		pwm->args.polarity = PWM_POLARITY_NORMAL;
> >  
> > +	pwm = pwm_request_from_chip(pc, args->args[0], NULL);
> > +	if (IS_ERR(pwm))
> > +		return pwm;
> > +  
> 
> Can't do that, because now you're dereferencing an uninitialized
> pointer.

Yes, forget this patch, it's not needed anyway since all PWM users are
now directly calling pwm_apply_args() after requesting the PWM. The bad
news is I broke bisectibilty :-(.

Still does not explain the bug reported by Mika.

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

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