* [PATCH v2] pwm: improve args checking in pwm_apply_state()
@ 2016-05-27 16:45 Brian Norris
2016-05-27 16:54 ` Boris Brezillon
` (2 more replies)
0 siblings, 3 replies; 13+ messages in thread
From: Brian Norris @ 2016-05-27 16:45 UTC (permalink / raw)
To: Thierry Reding
Cc: linux-pwm, linux-kernel, Brian Norris, Boris Brezillon,
Doug Anderson, Brian Norris
It seems like in the process of refactoring pwm_config() to utilize the
newly-introduced pwm_apply_state() API, some args/bounds checking was
dropped.
In particular, I noted that we are now allowing invalid period
selections. e.g.:
# echo 1 > /sys/class/pwm/pwmchip0/export
# cat /sys/class/pwm/pwmchip0/pwm1/period
100
# echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
[... driver may or may not reject the value, or trigger some logic bug ...]
It's better to see:
# echo 1 > /sys/class/pwm/pwmchip0/export
# cat /sys/class/pwm/pwmchip0/pwm1/period
100
# echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
-bash: echo: write error: Invalid argument
This patch reintroduces some bounds checks in both pwm_config() (for its
signed parameters; we don't want to convert negative values into large
unsigned values) and in pwm_apply_state() (which fix the above described
behavior, as well as other potential API misuses).
Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
Signed-off-by: Brian Norris <briannorris@chromium.org>
---
v2:
* changed subject, as this covers more scope now
* add Fixes tag, as this is a v4.7-rc regression
* add more bounds/args checks in pwm_apply_state() and pwm_config()
drivers/pwm/core.c | 3 ++-
include/linux/pwm.h | 3 +++
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index dba3843c53b8..ed337a8c34ab 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -457,7 +457,8 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
{
int err;
- if (!pwm)
+ if (!pwm || !state || !state->period ||
+ state->duty_cycle > state->period)
return -EINVAL;
if (!memcmp(state, &pwm->state, sizeof(*state)))
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 17018f3c066e..908b67c847cd 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -235,6 +235,9 @@ static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
if (!pwm)
return -EINVAL;
+ if (duty_ns < 0 || period_ns < 0)
+ return -EINVAL;
+
pwm_get_state(pwm, &state);
if (state.duty_cycle == duty_ns && state.period == period_ns)
return 0;
--
2.8.0.rc3.226.g39d4020
^ permalink raw reply related [flat|nested] 13+ messages in thread
* Re: [PATCH v2] pwm: improve args checking in pwm_apply_state()
2016-05-27 16:45 [PATCH v2] pwm: improve args checking in pwm_apply_state() Brian Norris
@ 2016-05-27 16:54 ` Boris Brezillon
2016-06-10 12:20 ` Thierry Reding
2016-06-21 14:42 ` Geert Uytterhoeven
2 siblings, 0 replies; 13+ messages in thread
From: Boris Brezillon @ 2016-05-27 16:54 UTC (permalink / raw)
To: Brian Norris
Cc: Thierry Reding, linux-pwm, linux-kernel, Brian Norris, Doug Anderson
On Fri, 27 May 2016 09:45:49 -0700
Brian Norris <briannorris@chromium.org> wrote:
> It seems like in the process of refactoring pwm_config() to utilize the
> newly-introduced pwm_apply_state() API, some args/bounds checking was
> dropped.
>
> In particular, I noted that we are now allowing invalid period
> selections. e.g.:
>
> # echo 1 > /sys/class/pwm/pwmchip0/export
> # cat /sys/class/pwm/pwmchip0/pwm1/period
> 100
> # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> [... driver may or may not reject the value, or trigger some logic bug ...]
>
> It's better to see:
>
> # echo 1 > /sys/class/pwm/pwmchip0/export
> # cat /sys/class/pwm/pwmchip0/pwm1/period
> 100
> # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> -bash: echo: write error: Invalid argument
>
> This patch reintroduces some bounds checks in both pwm_config() (for its
> signed parameters; we don't want to convert negative values into large
> unsigned values) and in pwm_apply_state() (which fix the above described
> behavior, as well as other potential API misuses).
>
> Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
> Signed-off-by: Brian Norris <briannorris@chromium.org>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Thanks,
Boris
> ---
> v2:
> * changed subject, as this covers more scope now
> * add Fixes tag, as this is a v4.7-rc regression
> * add more bounds/args checks in pwm_apply_state() and pwm_config()
>
> drivers/pwm/core.c | 3 ++-
> include/linux/pwm.h | 3 +++
> 2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> index dba3843c53b8..ed337a8c34ab 100644
> --- a/drivers/pwm/core.c
> +++ b/drivers/pwm/core.c
> @@ -457,7 +457,8 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
> {
> int err;
>
> - if (!pwm)
> + if (!pwm || !state || !state->period ||
> + state->duty_cycle > state->period)
> return -EINVAL;
>
> if (!memcmp(state, &pwm->state, sizeof(*state)))
> diff --git a/include/linux/pwm.h b/include/linux/pwm.h
> index 17018f3c066e..908b67c847cd 100644
> --- a/include/linux/pwm.h
> +++ b/include/linux/pwm.h
> @@ -235,6 +235,9 @@ static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
> if (!pwm)
> return -EINVAL;
>
> + if (duty_ns < 0 || period_ns < 0)
> + return -EINVAL;
> +
> pwm_get_state(pwm, &state);
> if (state.duty_cycle == duty_ns && state.period == period_ns)
> return 0;
--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v2] pwm: improve args checking in pwm_apply_state()
2016-05-27 16:45 [PATCH v2] pwm: improve args checking in pwm_apply_state() Brian Norris
2016-05-27 16:54 ` Boris Brezillon
@ 2016-06-10 12:20 ` Thierry Reding
2016-06-21 14:42 ` Geert Uytterhoeven
2 siblings, 0 replies; 13+ messages in thread
From: Thierry Reding @ 2016-06-10 12:20 UTC (permalink / raw)
To: Brian Norris
Cc: linux-pwm, linux-kernel, Brian Norris, Boris Brezillon, Doug Anderson
[-- Attachment #1: Type: text/plain, Size: 1569 bytes --]
On Fri, May 27, 2016 at 09:45:49AM -0700, Brian Norris wrote:
> It seems like in the process of refactoring pwm_config() to utilize the
> newly-introduced pwm_apply_state() API, some args/bounds checking was
> dropped.
>
> In particular, I noted that we are now allowing invalid period
> selections. e.g.:
>
> # echo 1 > /sys/class/pwm/pwmchip0/export
> # cat /sys/class/pwm/pwmchip0/pwm1/period
> 100
> # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> [... driver may or may not reject the value, or trigger some logic bug ...]
>
> It's better to see:
>
> # echo 1 > /sys/class/pwm/pwmchip0/export
> # cat /sys/class/pwm/pwmchip0/pwm1/period
> 100
> # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> -bash: echo: write error: Invalid argument
>
> This patch reintroduces some bounds checks in both pwm_config() (for its
> signed parameters; we don't want to convert negative values into large
> unsigned values) and in pwm_apply_state() (which fix the above described
> behavior, as well as other potential API misuses).
>
> Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
> Signed-off-by: Brian Norris <briannorris@chromium.org>
> ---
> v2:
> * changed subject, as this covers more scope now
> * add Fixes tag, as this is a v4.7-rc regression
> * add more bounds/args checks in pwm_apply_state() and pwm_config()
>
> drivers/pwm/core.c | 3 ++-
> include/linux/pwm.h | 3 +++
> 2 files changed, 5 insertions(+), 1 deletion(-)
Applied, thanks.
Thierry
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 819 bytes --]
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v2] pwm: improve args checking in pwm_apply_state()
2016-05-27 16:45 [PATCH v2] pwm: improve args checking in pwm_apply_state() Brian Norris
2016-05-27 16:54 ` Boris Brezillon
2016-06-10 12:20 ` Thierry Reding
@ 2016-06-21 14:42 ` Geert Uytterhoeven
2016-06-21 18:37 ` Brian Norris
2 siblings, 1 reply; 13+ messages in thread
From: Geert Uytterhoeven @ 2016-06-21 14:42 UTC (permalink / raw)
To: Brian Norris
Cc: Thierry Reding, Linux PWM List, linux-kernel, Brian Norris,
Boris Brezillon, Doug Anderson, linux-renesas-soc,
Laurent Pinchart
Hi Brian,
On Fri, May 27, 2016 at 6:45 PM, Brian Norris <briannorris@chromium.org> wrote:
> It seems like in the process of refactoring pwm_config() to utilize the
> newly-introduced pwm_apply_state() API, some args/bounds checking was
> dropped.
>
> In particular, I noted that we are now allowing invalid period
> selections. e.g.:
>
> # echo 1 > /sys/class/pwm/pwmchip0/export
> # cat /sys/class/pwm/pwmchip0/pwm1/period
> 100
> # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> [... driver may or may not reject the value, or trigger some logic bug ...]
>
> It's better to see:
>
> # echo 1 > /sys/class/pwm/pwmchip0/export
> # cat /sys/class/pwm/pwmchip0/pwm1/period
> 100
> # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> -bash: echo: write error: Invalid argument
>
> This patch reintroduces some bounds checks in both pwm_config() (for its
> signed parameters; we don't want to convert negative values into large
> unsigned values) and in pwm_apply_state() (which fix the above described
> behavior, as well as other potential API misuses).
>
> Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
> Signed-off-by: Brian Norris <briannorris@chromium.org>
> ---
> v2:
> * changed subject, as this covers more scope now
> * add Fixes tag, as this is a v4.7-rc regression
> * add more bounds/args checks in pwm_apply_state() and pwm_config()
>
> drivers/pwm/core.c | 3 ++-
> include/linux/pwm.h | 3 +++
> 2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> index dba3843c53b8..ed337a8c34ab 100644
> --- a/drivers/pwm/core.c
> +++ b/drivers/pwm/core.c
> @@ -457,7 +457,8 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
> {
> int err;
>
> - if (!pwm)
> + if (!pwm || !state || !state->period ||
> + state->duty_cycle > state->period)
> return -EINVAL;
This check breaks the LCD backlight on r8a7740/armadillo.
Apparently both period and duty_cycle are zero during the first invocation.
Later, these are initialized from DT, cfr.
pwms = <&tpu 2 33333 PWM_POLARITY_INVERTED>;
in arch/arm/boot/dts/r8a7740-armadillo800eva.dts.
With added debug printing, the difference between failure and success is:
renesas-tpu-pwm e6600000.pwm: TPU PWM -1 registered
tpu_pwm_request:223
pwm_apply_state:460: pwm backlight/2: period 0, duty_cycle 0
+Ignoring failure
+pwm_apply_state:479: polarity 0 -> 1
+tpu_pwm_set_polarity:343
+pwm_apply_state:502: period 0 -> 0
+pwm_apply_state:503: duty_cycle 0 -> 0
+pwm_apply_state:516: enabled 0 -> 0
pwm_config:238: pwm backlight/2: duty_ns 33333, period_ns 33333
pwm_apply_state:460: pwm backlight/2: period 33333, duty_cycle 33333
-pwm_apply_state:479: polarity 0 -> 0
+pwm_apply_state:479: polarity 1 -> 1
pwm_apply_state:502: period 0 -> 33333
pwm_apply_state:503: duty_cycle 0 -> 33333
tpu_pwm_config:267
pwm_apply_state:516: enabled 0 -> 0
pwm_apply_state:460: pwm backlight/2: period 33333, duty_cycle 33333
-pwm_apply_state:479: polarity 0 -> 0
+pwm_apply_state:479: polarity 1 -> 1
pwm_apply_state:502: period 33333 -> 33333
pwm_apply_state:503: duty_cycle 33333 -> 33333
pwm_apply_state:516: enabled 0 -> 1
tpu_pwm_enable:354
Sorry for not noticing last week, before it hit mainline.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v2] pwm: improve args checking in pwm_apply_state()
2016-06-21 14:42 ` Geert Uytterhoeven
@ 2016-06-21 18:37 ` Brian Norris
2016-06-21 21:22 ` Boris Brezillon
2016-06-22 8:04 ` Boris Brezillon
0 siblings, 2 replies; 13+ messages in thread
From: Brian Norris @ 2016-06-21 18:37 UTC (permalink / raw)
To: Geert Uytterhoeven, Boris Brezillon
Cc: Thierry Reding, Linux PWM List, linux-kernel, Brian Norris,
Boris Brezillon, Doug Anderson, linux-renesas-soc,
Laurent Pinchart
Hi Geert,
On Tue, Jun 21, 2016 at 04:42:04PM +0200, Geert Uytterhoeven wrote:
> On Fri, May 27, 2016 at 6:45 PM, Brian Norris <briannorris@chromium.org> wrote:
> > It seems like in the process of refactoring pwm_config() to utilize the
> > newly-introduced pwm_apply_state() API, some args/bounds checking was
> > dropped.
> >
> > In particular, I noted that we are now allowing invalid period
> > selections. e.g.:
> >
> > # echo 1 > /sys/class/pwm/pwmchip0/export
> > # cat /sys/class/pwm/pwmchip0/pwm1/period
> > 100
> > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> > [... driver may or may not reject the value, or trigger some logic bug ...]
> >
> > It's better to see:
> >
> > # echo 1 > /sys/class/pwm/pwmchip0/export
> > # cat /sys/class/pwm/pwmchip0/pwm1/period
> > 100
> > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> > -bash: echo: write error: Invalid argument
> >
> > This patch reintroduces some bounds checks in both pwm_config() (for its
> > signed parameters; we don't want to convert negative values into large
> > unsigned values) and in pwm_apply_state() (which fix the above described
> > behavior, as well as other potential API misuses).
> >
> > Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
> > Signed-off-by: Brian Norris <briannorris@chromium.org>
> > ---
> > v2:
> > * changed subject, as this covers more scope now
> > * add Fixes tag, as this is a v4.7-rc regression
> > * add more bounds/args checks in pwm_apply_state() and pwm_config()
> >
> > drivers/pwm/core.c | 3 ++-
> > include/linux/pwm.h | 3 +++
> > 2 files changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> > index dba3843c53b8..ed337a8c34ab 100644
> > --- a/drivers/pwm/core.c
> > +++ b/drivers/pwm/core.c
> > @@ -457,7 +457,8 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
> > {
> > int err;
> >
> > - if (!pwm)
> > + if (!pwm || !state || !state->period ||
> > + state->duty_cycle > state->period)
> > return -EINVAL;
>
> This check breaks the LCD backlight on r8a7740/armadillo.
> Apparently both period and duty_cycle are zero during the first invocation.
> Later, these are initialized from DT, cfr.
>
> pwms = <&tpu 2 33333 PWM_POLARITY_INVERTED>;
>
> in arch/arm/boot/dts/r8a7740-armadillo800eva.dts.
Hmm, this isn't super obvious how to best fix. On one hand, the
pwm_config() API used to reject period<=0, but on the other hand, I
think its replacement (pwm_apply_state()) is getting used in more places
than it used to be, and not all of them are really handling the "atomic
update" concept yet. Seems like a product of Boris's multi-phase attempt
to convert the PWM APIs to support atomic updates -- and many users
haven't really converted yet.
> With added debug printing, the difference between failure and success is:
>
> renesas-tpu-pwm e6600000.pwm: TPU PWM -1 registered
> tpu_pwm_request:223
> pwm_apply_state:460: pwm backlight/2: period 0, duty_cycle 0
> +Ignoring failure
> +pwm_apply_state:479: polarity 0 -> 1
> +tpu_pwm_set_polarity:343
> +pwm_apply_state:502: period 0 -> 0
> +pwm_apply_state:503: duty_cycle 0 -> 0
> +pwm_apply_state:516: enabled 0 -> 0
> pwm_config:238: pwm backlight/2: duty_ns 33333, period_ns 33333
> pwm_apply_state:460: pwm backlight/2: period 33333, duty_cycle 33333
> -pwm_apply_state:479: polarity 0 -> 0
> +pwm_apply_state:479: polarity 1 -> 1
> pwm_apply_state:502: period 0 -> 33333
> pwm_apply_state:503: duty_cycle 0 -> 33333
> tpu_pwm_config:267
> pwm_apply_state:516: enabled 0 -> 0
> pwm_apply_state:460: pwm backlight/2: period 33333, duty_cycle 33333
> -pwm_apply_state:479: polarity 0 -> 0
> +pwm_apply_state:479: polarity 1 -> 1
> pwm_apply_state:502: period 33333 -> 33333
> pwm_apply_state:503: duty_cycle 33333 -> 33333
> pwm_apply_state:516: enabled 0 -> 1
> tpu_pwm_enable:354
I'm not sure I 100% understand this debug log, but I think maybe the
problem is in pwm_apply_args(), which calls pwm_disable() and
pwm_set_polarity() sequentially, without ever configuring a period? What
if pwm_apply_args() were to configure the period for us?
Boris, any thoughts?
> Sorry for not noticing last week, before it hit mainline.
Sorry for the regression :(
Brian
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v2] pwm: improve args checking in pwm_apply_state()
2016-06-21 18:37 ` Brian Norris
@ 2016-06-21 21:22 ` Boris Brezillon
2016-06-22 8:04 ` Boris Brezillon
1 sibling, 0 replies; 13+ messages in thread
From: Boris Brezillon @ 2016-06-21 21:22 UTC (permalink / raw)
To: Brian Norris
Cc: Geert Uytterhoeven, Thierry Reding, Linux PWM List, linux-kernel,
Brian Norris, Doug Anderson, linux-renesas-soc, Laurent Pinchart
On Tue, 21 Jun 2016 11:37:31 -0700
Brian Norris <briannorris@chromium.org> wrote:
> Hi Geert,
>
> On Tue, Jun 21, 2016 at 04:42:04PM +0200, Geert Uytterhoeven wrote:
> > On Fri, May 27, 2016 at 6:45 PM, Brian Norris <briannorris@chromium.org> wrote:
> > > It seems like in the process of refactoring pwm_config() to utilize the
> > > newly-introduced pwm_apply_state() API, some args/bounds checking was
> > > dropped.
> > >
> > > In particular, I noted that we are now allowing invalid period
> > > selections. e.g.:
> > >
> > > # echo 1 > /sys/class/pwm/pwmchip0/export
> > > # cat /sys/class/pwm/pwmchip0/pwm1/period
> > > 100
> > > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> > > [... driver may or may not reject the value, or trigger some logic bug ...]
> > >
> > > It's better to see:
> > >
> > > # echo 1 > /sys/class/pwm/pwmchip0/export
> > > # cat /sys/class/pwm/pwmchip0/pwm1/period
> > > 100
> > > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> > > -bash: echo: write error: Invalid argument
> > >
> > > This patch reintroduces some bounds checks in both pwm_config() (for its
> > > signed parameters; we don't want to convert negative values into large
> > > unsigned values) and in pwm_apply_state() (which fix the above described
> > > behavior, as well as other potential API misuses).
> > >
> > > Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
> > > Signed-off-by: Brian Norris <briannorris@chromium.org>
> > > ---
> > > v2:
> > > * changed subject, as this covers more scope now
> > > * add Fixes tag, as this is a v4.7-rc regression
> > > * add more bounds/args checks in pwm_apply_state() and pwm_config()
> > >
> > > drivers/pwm/core.c | 3 ++-
> > > include/linux/pwm.h | 3 +++
> > > 2 files changed, 5 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> > > index dba3843c53b8..ed337a8c34ab 100644
> > > --- a/drivers/pwm/core.c
> > > +++ b/drivers/pwm/core.c
> > > @@ -457,7 +457,8 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
> > > {
> > > int err;
> > >
> > > - if (!pwm)
> > > + if (!pwm || !state || !state->period ||
> > > + state->duty_cycle > state->period)
> > > return -EINVAL;
> >
> > This check breaks the LCD backlight on r8a7740/armadillo.
> > Apparently both period and duty_cycle are zero during the first invocation.
> > Later, these are initialized from DT, cfr.
> >
> > pwms = <&tpu 2 33333 PWM_POLARITY_INVERTED>;
> >
> > in arch/arm/boot/dts/r8a7740-armadillo800eva.dts.
>
> Hmm, this isn't super obvious how to best fix. On one hand, the
> pwm_config() API used to reject period<=0, but on the other hand, I
> think its replacement (pwm_apply_state()) is getting used in more places
> than it used to be, and not all of them are really handling the "atomic
> update" concept yet. Seems like a product of Boris's multi-phase attempt
> to convert the PWM APIs to support atomic updates -- and many users
> haven't really converted yet.
>
> > With added debug printing, the difference between failure and success is:
> >
> > renesas-tpu-pwm e6600000.pwm: TPU PWM -1 registered
> > tpu_pwm_request:223
> > pwm_apply_state:460: pwm backlight/2: period 0, duty_cycle 0
> > +Ignoring failure
> > +pwm_apply_state:479: polarity 0 -> 1
> > +tpu_pwm_set_polarity:343
> > +pwm_apply_state:502: period 0 -> 0
> > +pwm_apply_state:503: duty_cycle 0 -> 0
> > +pwm_apply_state:516: enabled 0 -> 0
> > pwm_config:238: pwm backlight/2: duty_ns 33333, period_ns 33333
> > pwm_apply_state:460: pwm backlight/2: period 33333, duty_cycle 33333
> > -pwm_apply_state:479: polarity 0 -> 0
> > +pwm_apply_state:479: polarity 1 -> 1
> > pwm_apply_state:502: period 0 -> 33333
> > pwm_apply_state:503: duty_cycle 0 -> 33333
> > tpu_pwm_config:267
> > pwm_apply_state:516: enabled 0 -> 0
> > pwm_apply_state:460: pwm backlight/2: period 33333, duty_cycle 33333
> > -pwm_apply_state:479: polarity 0 -> 0
> > +pwm_apply_state:479: polarity 1 -> 1
> > pwm_apply_state:502: period 33333 -> 33333
> > pwm_apply_state:503: duty_cycle 33333 -> 33333
> > pwm_apply_state:516: enabled 0 -> 1
> > tpu_pwm_enable:354
>
> I'm not sure I 100% understand this debug log, but I think maybe the
> problem is in pwm_apply_args(), which calls pwm_disable() and
> pwm_set_polarity() sequentially, without ever configuring a period? What
> if pwm_apply_args() were to configure the period for us?
>
> Boris, any thoughts?
I think this is partly caused by this commit:
a8c3862551e0 ("pwm: Keep PWM state in sync with hardware state")
But again, we need that one if we don't want to override the current
PWM period with the pwm_args one when the driver support hardware
readout.
This leaves 2 choices:
1/ assign the period to pargs->period if ->get_state() is not
implemented
2/ remove the !period check in pwm_apply_state() when state->enabled is
false (do we really care if period = 0 when all we want to do is
disable the PWM?)
Thierry, what's you're opinion.
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v2] pwm: improve args checking in pwm_apply_state()
2016-06-21 18:37 ` Brian Norris
2016-06-21 21:22 ` Boris Brezillon
@ 2016-06-22 8:04 ` Boris Brezillon
2016-06-22 12:00 ` Thierry Reding
` (2 more replies)
1 sibling, 3 replies; 13+ messages in thread
From: Boris Brezillon @ 2016-06-22 8:04 UTC (permalink / raw)
To: Brian Norris
Cc: Geert Uytterhoeven, Thierry Reding, Linux PWM List, linux-kernel,
Brian Norris, Doug Anderson, linux-renesas-soc, Laurent Pinchart
On Tue, 21 Jun 2016 11:37:31 -0700
Brian Norris <briannorris@chromium.org> wrote:
> Hi Geert,
>
> On Tue, Jun 21, 2016 at 04:42:04PM +0200, Geert Uytterhoeven wrote:
> > On Fri, May 27, 2016 at 6:45 PM, Brian Norris <briannorris@chromium.org> wrote:
> > > It seems like in the process of refactoring pwm_config() to utilize the
> > > newly-introduced pwm_apply_state() API, some args/bounds checking was
> > > dropped.
> > >
> > > In particular, I noted that we are now allowing invalid period
> > > selections. e.g.:
> > >
> > > # echo 1 > /sys/class/pwm/pwmchip0/export
> > > # cat /sys/class/pwm/pwmchip0/pwm1/period
> > > 100
> > > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> > > [... driver may or may not reject the value, or trigger some logic bug ...]
> > >
> > > It's better to see:
> > >
> > > # echo 1 > /sys/class/pwm/pwmchip0/export
> > > # cat /sys/class/pwm/pwmchip0/pwm1/period
> > > 100
> > > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> > > -bash: echo: write error: Invalid argument
> > >
> > > This patch reintroduces some bounds checks in both pwm_config() (for its
> > > signed parameters; we don't want to convert negative values into large
> > > unsigned values) and in pwm_apply_state() (which fix the above described
> > > behavior, as well as other potential API misuses).
> > >
> > > Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
> > > Signed-off-by: Brian Norris <briannorris@chromium.org>
> > > ---
> > > v2:
> > > * changed subject, as this covers more scope now
> > > * add Fixes tag, as this is a v4.7-rc regression
> > > * add more bounds/args checks in pwm_apply_state() and pwm_config()
> > >
> > > drivers/pwm/core.c | 3 ++-
> > > include/linux/pwm.h | 3 +++
> > > 2 files changed, 5 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> > > index dba3843c53b8..ed337a8c34ab 100644
> > > --- a/drivers/pwm/core.c
> > > +++ b/drivers/pwm/core.c
> > > @@ -457,7 +457,8 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
> > > {
> > > int err;
> > >
> > > - if (!pwm)
> > > + if (!pwm || !state || !state->period ||
> > > + state->duty_cycle > state->period)
> > > return -EINVAL;
> >
> > This check breaks the LCD backlight on r8a7740/armadillo.
> > Apparently both period and duty_cycle are zero during the first invocation.
> > Later, these are initialized from DT, cfr.
> >
> > pwms = <&tpu 2 33333 PWM_POLARITY_INVERTED>;
> >
> > in arch/arm/boot/dts/r8a7740-armadillo800eva.dts.
>
> Hmm, this isn't super obvious how to best fix. On one hand, the
> pwm_config() API used to reject period<=0, but on the other hand, I
> think its replacement (pwm_apply_state()) is getting used in more places
> than it used to be, and not all of them are really handling the "atomic
> update" concept yet. Seems like a product of Boris's multi-phase attempt
> to convert the PWM APIs to support atomic updates -- and many users
> haven't really converted yet.
>
> > With added debug printing, the difference between failure and success is:
> >
> > renesas-tpu-pwm e6600000.pwm: TPU PWM -1 registered
> > tpu_pwm_request:223
> > pwm_apply_state:460: pwm backlight/2: period 0, duty_cycle 0
> > +Ignoring failure
> > +pwm_apply_state:479: polarity 0 -> 1
> > +tpu_pwm_set_polarity:343
> > +pwm_apply_state:502: period 0 -> 0
> > +pwm_apply_state:503: duty_cycle 0 -> 0
> > +pwm_apply_state:516: enabled 0 -> 0
> > pwm_config:238: pwm backlight/2: duty_ns 33333, period_ns 33333
> > pwm_apply_state:460: pwm backlight/2: period 33333, duty_cycle 33333
> > -pwm_apply_state:479: polarity 0 -> 0
> > +pwm_apply_state:479: polarity 1 -> 1
> > pwm_apply_state:502: period 0 -> 33333
> > pwm_apply_state:503: duty_cycle 0 -> 33333
> > tpu_pwm_config:267
> > pwm_apply_state:516: enabled 0 -> 0
> > pwm_apply_state:460: pwm backlight/2: period 33333, duty_cycle 33333
> > -pwm_apply_state:479: polarity 0 -> 0
> > +pwm_apply_state:479: polarity 1 -> 1
> > pwm_apply_state:502: period 33333 -> 33333
> > pwm_apply_state:503: duty_cycle 33333 -> 33333
> > pwm_apply_state:516: enabled 0 -> 1
> > tpu_pwm_enable:354
>
> I'm not sure I 100% understand this debug log, but I think maybe the
> problem is in pwm_apply_args(), which calls pwm_disable() and
> pwm_set_polarity() sequentially, without ever configuring a period? What
> if pwm_apply_args() were to configure the period for us?
>
> Boris, any thoughts?
>
I had second thoughts and I think you're right: pwm_apply_args()
should set the pargs.period period for us.
Here is a patch addressing that.
Geert, can you test it?
--->8---
>From 0610f7e24976e176054bce20445ff42d8aea9513 Mon Sep 17 00:00:00 2001
From: Boris Brezillon <boris.brezillon@free-electrons.com>
Date: Wed, 22 Jun 2016 09:25:14 +0200
Subject: [PATCH] pwm: Fix pwm_apply_args()
Commit 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic
updates"), implemented pwm_disable() as a wrapper around
pwm_apply_state(), and then, commit ef2bf4997f7d ("pwm: Improve args
checking in pwm_apply_state()") added missing checks on the ->period
value in pwm_apply_state() to ensure we were not passing inappropriate
values to the ->config() or ->apply() methods.
The conjunction of these 2 commits led to a case where pwm_disable()
was no longer succeeding, thus preventing the polarity setting done
in pwm_apply_args().
Set a valid period in pwm_apply_args() to ensure polarity setting
won't be rejected.
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Suggested-by: Brian Norris <briannorris@chromium.org>
Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
---
include/linux/pwm.h | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 908b67c847cd..c038ae36b10e 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -464,6 +464,8 @@ static inline bool pwm_can_sleep(struct pwm_device *pwm)
static inline void pwm_apply_args(struct pwm_device *pwm)
{
+ struct pwm_state state = { };
+
/*
* PWM users calling pwm_apply_args() expect to have a fresh config
* where the polarity and period are set according to pwm_args info.
@@ -476,18 +478,20 @@ static inline void pwm_apply_args(struct pwm_device *pwm)
* at startup (even if they are actually enabled), thus authorizing
* polarity setting.
*
- * Instead of setting ->enabled to false, we call pwm_disable()
- * before pwm_set_polarity() to ensure that everything is configured
- * as expected, and the PWM is really disabled when the user request
- * it.
+ * To fulfill this requirement, we apply a new state which disables
+ * the PWM device and set the reference period and polarity config.
*
* Note that PWM users requiring a smooth handover between the
* bootloader and the kernel (like critical regulators controlled by
* PWM devices) will have to switch to the atomic API and avoid calling
* pwm_apply_args().
*/
- pwm_disable(pwm);
- pwm_set_polarity(pwm, pwm->args.polarity);
+
+ state.enabled = false;
+ state.polarity = pwm->args.polarity;
+ state.period = pwm->args.period;
+
+ pwm_apply_state(pwm, &state);
}
struct pwm_lookup {
--
2.7.4
^ permalink raw reply related [flat|nested] 13+ messages in thread
* Re: [PATCH v2] pwm: improve args checking in pwm_apply_state()
2016-06-22 8:04 ` Boris Brezillon
@ 2016-06-22 12:00 ` Thierry Reding
2016-06-22 14:32 ` Geert Uytterhoeven
2016-06-22 19:16 ` Brian Norris
2 siblings, 0 replies; 13+ messages in thread
From: Thierry Reding @ 2016-06-22 12:00 UTC (permalink / raw)
To: Boris Brezillon
Cc: Brian Norris, Geert Uytterhoeven, Linux PWM List, linux-kernel,
Brian Norris, Doug Anderson, linux-renesas-soc, Laurent Pinchart
[-- Attachment #1: Type: text/plain, Size: 8120 bytes --]
On Wed, Jun 22, 2016 at 10:04:22AM +0200, Boris Brezillon wrote:
> On Tue, 21 Jun 2016 11:37:31 -0700
> Brian Norris <briannorris@chromium.org> wrote:
>
> > Hi Geert,
> >
> > On Tue, Jun 21, 2016 at 04:42:04PM +0200, Geert Uytterhoeven wrote:
> > > On Fri, May 27, 2016 at 6:45 PM, Brian Norris <briannorris@chromium.org> wrote:
> > > > It seems like in the process of refactoring pwm_config() to utilize the
> > > > newly-introduced pwm_apply_state() API, some args/bounds checking was
> > > > dropped.
> > > >
> > > > In particular, I noted that we are now allowing invalid period
> > > > selections. e.g.:
> > > >
> > > > # echo 1 > /sys/class/pwm/pwmchip0/export
> > > > # cat /sys/class/pwm/pwmchip0/pwm1/period
> > > > 100
> > > > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> > > > [... driver may or may not reject the value, or trigger some logic bug ...]
> > > >
> > > > It's better to see:
> > > >
> > > > # echo 1 > /sys/class/pwm/pwmchip0/export
> > > > # cat /sys/class/pwm/pwmchip0/pwm1/period
> > > > 100
> > > > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
> > > > -bash: echo: write error: Invalid argument
> > > >
> > > > This patch reintroduces some bounds checks in both pwm_config() (for its
> > > > signed parameters; we don't want to convert negative values into large
> > > > unsigned values) and in pwm_apply_state() (which fix the above described
> > > > behavior, as well as other potential API misuses).
> > > >
> > > > Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
> > > > Signed-off-by: Brian Norris <briannorris@chromium.org>
> > > > ---
> > > > v2:
> > > > * changed subject, as this covers more scope now
> > > > * add Fixes tag, as this is a v4.7-rc regression
> > > > * add more bounds/args checks in pwm_apply_state() and pwm_config()
> > > >
> > > > drivers/pwm/core.c | 3 ++-
> > > > include/linux/pwm.h | 3 +++
> > > > 2 files changed, 5 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> > > > index dba3843c53b8..ed337a8c34ab 100644
> > > > --- a/drivers/pwm/core.c
> > > > +++ b/drivers/pwm/core.c
> > > > @@ -457,7 +457,8 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
> > > > {
> > > > int err;
> > > >
> > > > - if (!pwm)
> > > > + if (!pwm || !state || !state->period ||
> > > > + state->duty_cycle > state->period)
> > > > return -EINVAL;
> > >
> > > This check breaks the LCD backlight on r8a7740/armadillo.
> > > Apparently both period and duty_cycle are zero during the first invocation.
> > > Later, these are initialized from DT, cfr.
> > >
> > > pwms = <&tpu 2 33333 PWM_POLARITY_INVERTED>;
> > >
> > > in arch/arm/boot/dts/r8a7740-armadillo800eva.dts.
> >
> > Hmm, this isn't super obvious how to best fix. On one hand, the
> > pwm_config() API used to reject period<=0, but on the other hand, I
> > think its replacement (pwm_apply_state()) is getting used in more places
> > than it used to be, and not all of them are really handling the "atomic
> > update" concept yet. Seems like a product of Boris's multi-phase attempt
> > to convert the PWM APIs to support atomic updates -- and many users
> > haven't really converted yet.
> >
> > > With added debug printing, the difference between failure and success is:
> > >
> > > renesas-tpu-pwm e6600000.pwm: TPU PWM -1 registered
> > > tpu_pwm_request:223
> > > pwm_apply_state:460: pwm backlight/2: period 0, duty_cycle 0
> > > +Ignoring failure
> > > +pwm_apply_state:479: polarity 0 -> 1
> > > +tpu_pwm_set_polarity:343
> > > +pwm_apply_state:502: period 0 -> 0
> > > +pwm_apply_state:503: duty_cycle 0 -> 0
> > > +pwm_apply_state:516: enabled 0 -> 0
> > > pwm_config:238: pwm backlight/2: duty_ns 33333, period_ns 33333
> > > pwm_apply_state:460: pwm backlight/2: period 33333, duty_cycle 33333
> > > -pwm_apply_state:479: polarity 0 -> 0
> > > +pwm_apply_state:479: polarity 1 -> 1
> > > pwm_apply_state:502: period 0 -> 33333
> > > pwm_apply_state:503: duty_cycle 0 -> 33333
> > > tpu_pwm_config:267
> > > pwm_apply_state:516: enabled 0 -> 0
> > > pwm_apply_state:460: pwm backlight/2: period 33333, duty_cycle 33333
> > > -pwm_apply_state:479: polarity 0 -> 0
> > > +pwm_apply_state:479: polarity 1 -> 1
> > > pwm_apply_state:502: period 33333 -> 33333
> > > pwm_apply_state:503: duty_cycle 33333 -> 33333
> > > pwm_apply_state:516: enabled 0 -> 1
> > > tpu_pwm_enable:354
> >
> > I'm not sure I 100% understand this debug log, but I think maybe the
> > problem is in pwm_apply_args(), which calls pwm_disable() and
> > pwm_set_polarity() sequentially, without ever configuring a period? What
> > if pwm_apply_args() were to configure the period for us?
> >
> > Boris, any thoughts?
> >
>
> I had second thoughts and I think you're right: pwm_apply_args()
> should set the pargs.period period for us.
>
> Here is a patch addressing that.
>
> Geert, can you test it?
>
> --->8---
> From 0610f7e24976e176054bce20445ff42d8aea9513 Mon Sep 17 00:00:00 2001
> From: Boris Brezillon <boris.brezillon@free-electrons.com>
> Date: Wed, 22 Jun 2016 09:25:14 +0200
> Subject: [PATCH] pwm: Fix pwm_apply_args()
>
> Commit 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic
> updates"), implemented pwm_disable() as a wrapper around
> pwm_apply_state(), and then, commit ef2bf4997f7d ("pwm: Improve args
> checking in pwm_apply_state()") added missing checks on the ->period
> value in pwm_apply_state() to ensure we were not passing inappropriate
> values to the ->config() or ->apply() methods.
>
> The conjunction of these 2 commits led to a case where pwm_disable()
> was no longer succeeding, thus preventing the polarity setting done
> in pwm_apply_args().
>
> Set a valid period in pwm_apply_args() to ensure polarity setting
> won't be rejected.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Suggested-by: Brian Norris <briannorris@chromium.org>
> Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
> ---
> include/linux/pwm.h | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/pwm.h b/include/linux/pwm.h
> index 908b67c847cd..c038ae36b10e 100644
> --- a/include/linux/pwm.h
> +++ b/include/linux/pwm.h
> @@ -464,6 +464,8 @@ static inline bool pwm_can_sleep(struct pwm_device *pwm)
>
> static inline void pwm_apply_args(struct pwm_device *pwm)
> {
> + struct pwm_state state = { };
> +
> /*
> * PWM users calling pwm_apply_args() expect to have a fresh config
> * where the polarity and period are set according to pwm_args info.
> @@ -476,18 +478,20 @@ static inline void pwm_apply_args(struct pwm_device *pwm)
> * at startup (even if they are actually enabled), thus authorizing
> * polarity setting.
> *
> - * Instead of setting ->enabled to false, we call pwm_disable()
> - * before pwm_set_polarity() to ensure that everything is configured
> - * as expected, and the PWM is really disabled when the user request
> - * it.
> + * To fulfill this requirement, we apply a new state which disables
> + * the PWM device and set the reference period and polarity config.
> *
> * Note that PWM users requiring a smooth handover between the
> * bootloader and the kernel (like critical regulators controlled by
> * PWM devices) will have to switch to the atomic API and avoid calling
> * pwm_apply_args().
> */
> - pwm_disable(pwm);
> - pwm_set_polarity(pwm, pwm->args.polarity);
> +
> + state.enabled = false;
> + state.polarity = pwm->args.polarity;
> + state.period = pwm->args.period;
> +
> + pwm_apply_state(pwm, &state);
> }
>
> struct pwm_lookup {
This looks reasonable to me. I'll wait for a Tested-by from Geert before
applying, though.
Thierry
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 819 bytes --]
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v2] pwm: improve args checking in pwm_apply_state()
2016-06-22 8:04 ` Boris Brezillon
2016-06-22 12:00 ` Thierry Reding
@ 2016-06-22 14:32 ` Geert Uytterhoeven
2016-06-22 19:16 ` Brian Norris
2 siblings, 0 replies; 13+ messages in thread
From: Geert Uytterhoeven @ 2016-06-22 14:32 UTC (permalink / raw)
To: Boris Brezillon
Cc: Brian Norris, Thierry Reding, Linux PWM List, linux-kernel,
Brian Norris, Doug Anderson, linux-renesas-soc, Laurent Pinchart
Hi Boris,
On Wed, Jun 22, 2016 at 10:04 AM, Boris Brezillon
<boris.brezillon@free-electrons.com> wrote:
> On Tue, 21 Jun 2016 11:37:31 -0700
> Brian Norris <briannorris@chromium.org> wrote:
>> On Tue, Jun 21, 2016 at 04:42:04PM +0200, Geert Uytterhoeven wrote:
>> > On Fri, May 27, 2016 at 6:45 PM, Brian Norris <briannorris@chromium.org> wrote:
>> > > It seems like in the process of refactoring pwm_config() to utilize the
>> > > newly-introduced pwm_apply_state() API, some args/bounds checking was
>> > > dropped.
>> > >
>> > > In particular, I noted that we are now allowing invalid period
>> > > selections. e.g.:
>> > >
>> > > # echo 1 > /sys/class/pwm/pwmchip0/export
>> > > # cat /sys/class/pwm/pwmchip0/pwm1/period
>> > > 100
>> > > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
>> > > [... driver may or may not reject the value, or trigger some logic bug ...]
>> > >
>> > > It's better to see:
>> > >
>> > > # echo 1 > /sys/class/pwm/pwmchip0/export
>> > > # cat /sys/class/pwm/pwmchip0/pwm1/period
>> > > 100
>> > > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle
>> > > -bash: echo: write error: Invalid argument
>> > >
>> > > This patch reintroduces some bounds checks in both pwm_config() (for its
>> > > signed parameters; we don't want to convert negative values into large
>> > > unsigned values) and in pwm_apply_state() (which fix the above described
>> > > behavior, as well as other potential API misuses).
>> > >
>> > > Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
>> > > Signed-off-by: Brian Norris <briannorris@chromium.org>
>> > > ---
>> > > v2:
>> > > * changed subject, as this covers more scope now
>> > > * add Fixes tag, as this is a v4.7-rc regression
>> > > * add more bounds/args checks in pwm_apply_state() and pwm_config()
>> > >
>> > > drivers/pwm/core.c | 3 ++-
>> > > include/linux/pwm.h | 3 +++
>> > > 2 files changed, 5 insertions(+), 1 deletion(-)
>> > >
>> > > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
>> > > index dba3843c53b8..ed337a8c34ab 100644
>> > > --- a/drivers/pwm/core.c
>> > > +++ b/drivers/pwm/core.c
>> > > @@ -457,7 +457,8 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
>> > > {
>> > > int err;
>> > >
>> > > - if (!pwm)
>> > > + if (!pwm || !state || !state->period ||
>> > > + state->duty_cycle > state->period)
>> > > return -EINVAL;
>> >
>> > This check breaks the LCD backlight on r8a7740/armadillo.
>> I'm not sure I 100% understand this debug log, but I think maybe the
>> problem is in pwm_apply_args(), which calls pwm_disable() and
>> pwm_set_polarity() sequentially, without ever configuring a period? What
>> if pwm_apply_args() were to configure the period for us?
>>
>> Boris, any thoughts?
>>
>
> I had second thoughts and I think you're right: pwm_apply_args()
> should set the pargs.period period for us.
>
> Here is a patch addressing that.
>
> Geert, can you test it?
>
> --->8---
> From 0610f7e24976e176054bce20445ff42d8aea9513 Mon Sep 17 00:00:00 2001
> From: Boris Brezillon <boris.brezillon@free-electrons.com>
> Date: Wed, 22 Jun 2016 09:25:14 +0200
> Subject: [PATCH] pwm: Fix pwm_apply_args()
>
> Commit 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic
> updates"), implemented pwm_disable() as a wrapper around
> pwm_apply_state(), and then, commit ef2bf4997f7d ("pwm: Improve args
> checking in pwm_apply_state()") added missing checks on the ->period
> value in pwm_apply_state() to ensure we were not passing inappropriate
> values to the ->config() or ->apply() methods.
>
> The conjunction of these 2 commits led to a case where pwm_disable()
> was no longer succeeding, thus preventing the polarity setting done
> in pwm_apply_args().
>
> Set a valid period in pwm_apply_args() to ensure polarity setting
> won't be rejected.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Suggested-by: Brian Norris <briannorris@chromium.org>
> Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v2] pwm: improve args checking in pwm_apply_state()
2016-06-22 8:04 ` Boris Brezillon
2016-06-22 12:00 ` Thierry Reding
2016-06-22 14:32 ` Geert Uytterhoeven
@ 2016-06-22 19:16 ` Brian Norris
2016-06-22 20:41 ` Boris Brezillon
2 siblings, 1 reply; 13+ messages in thread
From: Brian Norris @ 2016-06-22 19:16 UTC (permalink / raw)
To: Boris Brezillon
Cc: Geert Uytterhoeven, Thierry Reding, Linux PWM List, linux-kernel,
Brian Norris, Doug Anderson, linux-renesas-soc, Laurent Pinchart
On Wed, Jun 22, 2016 at 10:04:22AM +0200, Boris Brezillon wrote:
> From 0610f7e24976e176054bce20445ff42d8aea9513 Mon Sep 17 00:00:00 2001
> From: Boris Brezillon <boris.brezillon@free-electrons.com>
> Date: Wed, 22 Jun 2016 09:25:14 +0200
> Subject: [PATCH] pwm: Fix pwm_apply_args()
>
> Commit 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic
> updates"), implemented pwm_disable() as a wrapper around
> pwm_apply_state(), and then, commit ef2bf4997f7d ("pwm: Improve args
> checking in pwm_apply_state()") added missing checks on the ->period
> value in pwm_apply_state() to ensure we were not passing inappropriate
> values to the ->config() or ->apply() methods.
>
> The conjunction of these 2 commits led to a case where pwm_disable()
> was no longer succeeding, thus preventing the polarity setting done
> in pwm_apply_args().
>
> Set a valid period in pwm_apply_args() to ensure polarity setting
> won't be rejected.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Suggested-by: Brian Norris <briannorris@chromium.org>
> Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
> ---
> include/linux/pwm.h | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/pwm.h b/include/linux/pwm.h
> index 908b67c847cd..c038ae36b10e 100644
> --- a/include/linux/pwm.h
> +++ b/include/linux/pwm.h
> @@ -464,6 +464,8 @@ static inline bool pwm_can_sleep(struct pwm_device *pwm)
>
> static inline void pwm_apply_args(struct pwm_device *pwm)
> {
> + struct pwm_state state = { };
> +
> /*
> * PWM users calling pwm_apply_args() expect to have a fresh config
> * where the polarity and period are set according to pwm_args info.
> @@ -476,18 +478,20 @@ static inline void pwm_apply_args(struct pwm_device *pwm)
> * at startup (even if they are actually enabled), thus authorizing
> * polarity setting.
> *
> - * Instead of setting ->enabled to false, we call pwm_disable()
> - * before pwm_set_polarity() to ensure that everything is configured
> - * as expected, and the PWM is really disabled when the user request
> - * it.
I was confused by this original text when reading it the first time. I
like the replacement text and implementation, as it seems to make more
sense.
> + * To fulfill this requirement, we apply a new state which disables
> + * the PWM device and set the reference period and polarity config.
> *
> * Note that PWM users requiring a smooth handover between the
> * bootloader and the kernel (like critical regulators controlled by
> * PWM devices) will have to switch to the atomic API and avoid calling
> * pwm_apply_args().
> */
> - pwm_disable(pwm);
> - pwm_set_polarity(pwm, pwm->args.polarity);
Notably, you're dropping the 'if (!pwm) { }' safety checks that are part
of pwm_disable() and pwm_set_polarity(). But I don't think there should
be any users relying on that.
> +
> + state.enabled = false;
> + state.polarity = pwm->args.polarity;
> + state.period = pwm->args.period;
> +
> + pwm_apply_state(pwm, &state);
> }
>
> struct pwm_lookup {
Reviewed-by: Brian Norris <briannorris@chromium.org>
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v2] pwm: improve args checking in pwm_apply_state()
2016-06-22 19:16 ` Brian Norris
@ 2016-06-22 20:41 ` Boris Brezillon
2016-06-22 20:46 ` Brian Norris
0 siblings, 1 reply; 13+ messages in thread
From: Boris Brezillon @ 2016-06-22 20:41 UTC (permalink / raw)
To: Brian Norris
Cc: Geert Uytterhoeven, Thierry Reding, Linux PWM List, linux-kernel,
Brian Norris, Doug Anderson, linux-renesas-soc, Laurent Pinchart
On Wed, 22 Jun 2016 12:16:59 -0700
Brian Norris <briannorris@chromium.org> wrote:
> On Wed, Jun 22, 2016 at 10:04:22AM +0200, Boris Brezillon wrote:
> > From 0610f7e24976e176054bce20445ff42d8aea9513 Mon Sep 17 00:00:00 2001
> > From: Boris Brezillon <boris.brezillon@free-electrons.com>
> > Date: Wed, 22 Jun 2016 09:25:14 +0200
> > Subject: [PATCH] pwm: Fix pwm_apply_args()
> >
> > Commit 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic
> > updates"), implemented pwm_disable() as a wrapper around
> > pwm_apply_state(), and then, commit ef2bf4997f7d ("pwm: Improve args
> > checking in pwm_apply_state()") added missing checks on the ->period
> > value in pwm_apply_state() to ensure we were not passing inappropriate
> > values to the ->config() or ->apply() methods.
> >
> > The conjunction of these 2 commits led to a case where pwm_disable()
> > was no longer succeeding, thus preventing the polarity setting done
> > in pwm_apply_args().
> >
> > Set a valid period in pwm_apply_args() to ensure polarity setting
> > won't be rejected.
> >
> > Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> > Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> > Suggested-by: Brian Norris <briannorris@chromium.org>
> > Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates")
> > ---
> > include/linux/pwm.h | 16 ++++++++++------
> > 1 file changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/linux/pwm.h b/include/linux/pwm.h
> > index 908b67c847cd..c038ae36b10e 100644
> > --- a/include/linux/pwm.h
> > +++ b/include/linux/pwm.h
> > @@ -464,6 +464,8 @@ static inline bool pwm_can_sleep(struct pwm_device *pwm)
> >
> > static inline void pwm_apply_args(struct pwm_device *pwm)
> > {
> > + struct pwm_state state = { };
> > +
> > /*
> > * PWM users calling pwm_apply_args() expect to have a fresh config
> > * where the polarity and period are set according to pwm_args info.
> > @@ -476,18 +478,20 @@ static inline void pwm_apply_args(struct pwm_device *pwm)
> > * at startup (even if they are actually enabled), thus authorizing
> > * polarity setting.
> > *
> > - * Instead of setting ->enabled to false, we call pwm_disable()
> > - * before pwm_set_polarity() to ensure that everything is configured
> > - * as expected, and the PWM is really disabled when the user request
> > - * it.
>
> I was confused by this original text when reading it the first time. I
> like the replacement text and implementation, as it seems to make more
> sense.
Well, it should have been done this way from the beginning, but
pwm_apply_args() was introduced before the commit introducing the atomic
APIs, and I forgot to update it when moving to the atomic approach :-/.
>
> > + * To fulfill this requirement, we apply a new state which disables
> > + * the PWM device and set the reference period and polarity config.
> > *
> > * Note that PWM users requiring a smooth handover between the
> > * bootloader and the kernel (like critical regulators controlled by
> > * PWM devices) will have to switch to the atomic API and avoid calling
> > * pwm_apply_args().
> > */
> > - pwm_disable(pwm);
> > - pwm_set_polarity(pwm, pwm->args.polarity);
>
> Notably, you're dropping the 'if (!pwm) { }' safety checks that are part
> of pwm_disable() and pwm_set_polarity(). But I don't think there should
> be any users relying on that.
Indeed. I can add it back here if you prefer, but honestly, PWM users
that are not checking the value returned by pwm_get() should be
considered buggy IMHO, and a NULL pointer exception is a good way to
make people realize they are not properly using the API :).
>
> > +
> > + state.enabled = false;
> > + state.polarity = pwm->args.polarity;
> > + state.period = pwm->args.period;
> > +
> > + pwm_apply_state(pwm, &state);
> > }
> >
> > struct pwm_lookup {
>
> Reviewed-by: Brian Norris <briannorris@chromium.org>
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v2] pwm: improve args checking in pwm_apply_state()
2016-06-22 20:41 ` Boris Brezillon
@ 2016-06-22 20:46 ` Brian Norris
2016-06-23 16:55 ` Thierry Reding
0 siblings, 1 reply; 13+ messages in thread
From: Brian Norris @ 2016-06-22 20:46 UTC (permalink / raw)
To: Boris Brezillon
Cc: Geert Uytterhoeven, Thierry Reding, Linux PWM List, linux-kernel,
Brian Norris, Doug Anderson, linux-renesas-soc, Laurent Pinchart
On Wed, Jun 22, 2016 at 10:41:14PM +0200, Boris Brezillon wrote:
> On Wed, 22 Jun 2016 12:16:59 -0700
> Brian Norris <briannorris@chromium.org> wrote:
> > Notably, you're dropping the 'if (!pwm) { }' safety checks that are part
> > of pwm_disable() and pwm_set_polarity(). But I don't think there should
> > be any users relying on that.
>
> Indeed. I can add it back here if you prefer,
Nah, that's ok. I just had to say it anyway :)
> but honestly, PWM users
> that are not checking the value returned by pwm_get() should be
> considered buggy IMHO, and a NULL pointer exception is a good way to
> make people realize they are not properly using the API :).
Seems OK.
Brian
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH v2] pwm: improve args checking in pwm_apply_state()
2016-06-22 20:46 ` Brian Norris
@ 2016-06-23 16:55 ` Thierry Reding
0 siblings, 0 replies; 13+ messages in thread
From: Thierry Reding @ 2016-06-23 16:55 UTC (permalink / raw)
To: Brian Norris
Cc: Boris Brezillon, Geert Uytterhoeven, Linux PWM List,
linux-kernel, Brian Norris, Doug Anderson, linux-renesas-soc,
Laurent Pinchart
[-- Attachment #1: Type: text/plain, Size: 987 bytes --]
On Wed, Jun 22, 2016 at 01:46:48PM -0700, Brian Norris wrote:
> On Wed, Jun 22, 2016 at 10:41:14PM +0200, Boris Brezillon wrote:
> > On Wed, 22 Jun 2016 12:16:59 -0700
> > Brian Norris <briannorris@chromium.org> wrote:
> > > Notably, you're dropping the 'if (!pwm) { }' safety checks that are part
> > > of pwm_disable() and pwm_set_polarity(). But I don't think there should
> > > be any users relying on that.
> >
> > Indeed. I can add it back here if you prefer,
>
> Nah, that's ok. I just had to say it anyway :)
>
> > but honestly, PWM users
> > that are not checking the value returned by pwm_get() should be
> > considered buggy IMHO, and a NULL pointer exception is a good way to
> > make people realize they are not properly using the API :).
>
> Seems OK.
I've applied this to my fixes branch, and I'll let it cook in linux-next
for a little while, then send it off to Linus for v4.7-rc6 next week if
no further fallout is caused by this.
Thierry
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^ permalink raw reply [flat|nested] 13+ messages in thread
end of thread, other threads:[~2016-06-23 16:55 UTC | newest]
Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-05-27 16:45 [PATCH v2] pwm: improve args checking in pwm_apply_state() Brian Norris
2016-05-27 16:54 ` Boris Brezillon
2016-06-10 12:20 ` Thierry Reding
2016-06-21 14:42 ` Geert Uytterhoeven
2016-06-21 18:37 ` Brian Norris
2016-06-21 21:22 ` Boris Brezillon
2016-06-22 8:04 ` Boris Brezillon
2016-06-22 12:00 ` Thierry Reding
2016-06-22 14:32 ` Geert Uytterhoeven
2016-06-22 19:16 ` Brian Norris
2016-06-22 20:41 ` Boris Brezillon
2016-06-22 20:46 ` Brian Norris
2016-06-23 16:55 ` Thierry Reding
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