Messages in this thread | | | Subject | Re: [RESEND PATCH] Revert "pwm: Set class for exported channels in sysfs" | From | Fabrice Gasnier <> | Date | Mon, 24 Sep 2018 15:59:03 +0200 |
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On 09/24/2018 01:53 PM, Thierry Reding wrote: > On Fri, Sep 21, 2018 at 04:02:47PM +0200, Fabrice Gasnier wrote: >> This reverts commit 7e5d1fd75c3dde9fc10c4472b9368089d1b81d00 as it causes >> regression with multiple pwm chip. It creates a new entry in >> '/sys/class/pwm' every time a 'pwmX' is exported with 'echo X > export': >> - 1st time export will create an entry in /sys/class/pwm/pwmX >> - when another export happens on another pwmchip, it can't be created >> (e.g. -EEXIST) >> >> This also changes existing ABI (Documentation/ABI/testing/sysfs-class-pwm): >> - pmwX should be there: /sys/class/pwm/pwmchipN/pwmX >> >> 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... >> >> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com> >> --- >> drivers/pwm/sysfs.c | 1 - >> 1 file changed, 1 deletion(-) > > Can we come up with an alternative that allows us to have both? We want > uevent and proper sysfs creation, or is that not possible?
Hi Thierry, all,
With current approach: - "export->child.class = parent->class" - ABI (e.g. "pwm%d") device name isn't unique with multiple pwm chip. I think this is not possible.
Trying to think of an alternative... I just did a quick test, by changing device name, to take pwmchip into account: + export->child.class = parent->class; export->child.release = pwm_export_release; export->child.parent = parent; export->child.devt = MKDEV(0, 0); export->child.groups = pwm_groups; - dev_set_name(&export->child, "pwm%u", pwm->hwpwm); + dev_set_name(&export->child, "pwmchip%d-pwm%u", chip->base, pwm->hwpwm);
But this also impacts existing ABI :-( Would you have suggestions to send an uevent, without modifying ABI ?
Please advise, Best regards, Fabrice
> > Thierry >
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