linux-kernel - Re: [RESEND PATCH] Revert "pwm: Set class for exported channels in sysfs"

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Date:   Mon, 24 Sep 2018 13:53:01 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Fabrice Gasnier <fabrice.gasnier@...com>
Cc:     stefan.wahren@...e.com, gohai@...zessiv.net,
        hsweeten@...ionengravers.com, gottfried.haider@...il.com,
        loic.pallardy@...com, broonie@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pwm@...r.kernel.org
Subject: Re: [RESEND PATCH] Revert "pwm: Set class for exported channels in
 sysfs"

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@...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?

Thierry

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