| Message ID | 1538400237-28766-2-git-send-email-fabrice.gasnier@st.com |
|---|---|
| State | Accepted |
| Headers | show |
| Series | pwm: sysfs: fix exporting PWM channel | expand |
On 1.10.2018 15:23, Fabrice Gasnier wrote: > This reverts commit 7e5d1fd75c3dde9fc10c4472b9368089d1b81d00 ("pwm: Set > class for exported channels in sysfs") as it causes regression with > multiple pwm chip[1], when exporting a pwm channel (echo X > export): > > - ABI (Documentation/ABI/testing/sysfs-class-pwm) states pwmX should be > created in /sys/class/pwm/pwmchipN/pwmX > - Reverted patch causes new entry to be also created directly in > /sys/class/pwm/pwmX > - 1st time, exporting pwmX will create an entry in /sys/class/pwm/pwmX > - class attributes are added under pwmX folder, such as export, unexport > npwm, symlinks. This is wrong as it belongs to pwmchipN. It may cause > bad behavior and report wrong values. > - when another export happens on another pwmchip, it can't be created > (e.g. -EEXIST). This is causing the issue with multiple pwmchip. > > Example on stm32 (stm32429i-eval) platform: > $ ls /sys/class/pwm > pwmchip0 pwmchip4 > > $ cd /sys/class/pwm/pwmchip0/ > $ echo 0 > export > $ ls /sys/class/pwm > pwm0 pwmchip0 pwmchip4 > > $ cd /sys/class/pwm/pwmchip4/ > $ echo 0 > export > sysfs: cannot create duplicate filename '/class/pwm/pwm0' > ...Exception stack follows... > > This is also seen on other platform [2] > > [1] https://lkml.org/lkml/2018/9/25/713 > [2] https://lkml.org/lkml/2018/9/25/447 > > Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com> > Tested-by: Gottfried Haider <gottfried.haider@gmail.com> Tested-by: Michal Vokáč <michal.vokac@ysoft.com> > --- > drivers/pwm/sysfs.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/drivers/pwm/sysfs.c b/drivers/pwm/sysfs.c > index 7c71cdb..4726d43 100644 > --- a/drivers/pwm/sysfs.c > +++ b/drivers/pwm/sysfs.c > @@ -263,7 +263,6 @@ static int pwm_export_child(struct device *parent, struct pwm_device *pwm) > export->pwm = pwm; > mutex_init(&export->lock); > > - export->child.class = parent->class; > export->child.release = pwm_export_release; > export->child.parent = parent; > export->child.devt = MKDEV(0, 0); >
diff --git a/drivers/pwm/sysfs.c b/drivers/pwm/sysfs.c index 7c71cdb..4726d43 100644 --- a/drivers/pwm/sysfs.c +++ b/drivers/pwm/sysfs.c @@ -263,7 +263,6 @@ static int pwm_export_child(struct device *parent, struct pwm_device *pwm) export->pwm = pwm; mutex_init(&export->lock); - export->child.class = parent->class; export->child.release = pwm_export_release; export->child.parent = parent; export->child.devt = MKDEV(0, 0);
This reverts commit 7e5d1fd75c3dde9fc10c4472b9368089d1b81d00 ("pwm: Set class for exported channels in sysfs") as it causes regression with multiple pwm chip[1], when exporting a pwm channel (echo X > export): - ABI (Documentation/ABI/testing/sysfs-class-pwm) states pwmX should be created in /sys/class/pwm/pwmchipN/pwmX - Reverted patch causes new entry to be also created directly in /sys/class/pwm/pwmX - 1st time, exporting pwmX will create an entry in /sys/class/pwm/pwmX - class attributes are added under pwmX folder, such as export, unexport npwm, symlinks. This is wrong as it belongs to pwmchipN. It may cause bad behavior and report wrong values. - when another export happens on another pwmchip, it can't be created (e.g. -EEXIST). This is causing the issue with multiple pwmchip. Example on stm32 (stm32429i-eval) platform: $ ls /sys/class/pwm pwmchip0 pwmchip4 $ cd /sys/class/pwm/pwmchip0/ $ echo 0 > export $ ls /sys/class/pwm pwm0 pwmchip0 pwmchip4 $ cd /sys/class/pwm/pwmchip4/ $ echo 0 > export sysfs: cannot create duplicate filename '/class/pwm/pwm0' ...Exception stack follows... This is also seen on other platform [2] [1] https://lkml.org/lkml/2018/9/25/713 [2] https://lkml.org/lkml/2018/9/25/447 Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com> Tested-by: Gottfried Haider <gottfried.haider@gmail.com> --- drivers/pwm/sysfs.c | 1 - 1 file changed, 1 deletion(-)