Re: Handle pwm with sysfs with recent kernel

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

Hello,

On Wed, Jan 09, 2019 at 09:25:31AM +0100, Lothar Waßmann wrote:
> Hi,
> 
> On Tue, 8 Jan 2019 23:21:02 +0100 Uwe Kleine-König wrote:
> > On Tue, Jan 08, 2019 at 11:07:39AM +0100, Arthur LAMBERT wrote:
> > > Then I have another issue when I try to enable my pwm :
> > > 
> > > # ls /sys/class/pwm/
> > > pwmchip0  pwmchip2  pwmchip4  pwmchip6
> > > pwmchip1  pwmchip3  pwmchip5  pwmchip7
> > > # echo 0 > /sys/class/pwm/pwmchip0/export
> > > # echo 1 > /sys/class/pwm/pwmchip0/pwm0/enable
> > > -sh: write error: Invalid argument  
> > 
> > Just a guess: did you check that /sys/class/pwm/pwmchip0/pwm0/enable
> > actually exists?
> > 
> If not, the error message would be 'No such file or directory' rather
> than "Invalid argument".

Then "Invalid argument" means that either the "1" couldn't be parsed as
an integer 1 or 0 (no) or that pwm_apply_state returned -EINVAL. What
type of pwm are we talking about (i.e. which driver is responsible for
pwmchip0)? Hmm, that machine is an imx6ul, looking at the pwm-imx driver
there doesn't seem to be a path through the .apply callback that returns
-EINVAL. Would you care to add a few printk in
drivers/pwm/sysfs.c:enable_store() that show where the -EINVAL comes
from?

Best regards
Uwe

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Pengutronix e.K.                           | Uwe Kleine-König            |
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