On Wed, Sep 30, 2020 at 11:52:04AM +0200, Greg Kroah-Hartman wrote: > On Wed, Sep 30, 2020 at 11:41:46AM +0200, Uwe Kleine-König wrote: > > Hello, > > > > I added Greg Kroah-Hartman who I discussed this with via irc a bit to > > Cc:. > > > > On Wed, Sep 30, 2020 at 11:20:56AM +0200, Lars Poeschel wrote: > > > thank you for your review! > > > > > > On Wed, Sep 30, 2020 at 08:57:26AM +0200, Uwe Kleine-König wrote: > > > > On Tue, Sep 29, 2020 at 02:19:53PM +0200, poesc...@lemonage.de wrote: > > > > > From: Lars Poeschel <poesc...@lemonage.de> > > > > > > > > > > This adds a class to exported pwm devices. > > > > > Exporting a pwm through sysfs did not yield udev events. The > > > > > > > > I wonder what is your use-case here. This for sure also has a place to > > > > be mentioned in the commit log. I suspect there is a better way to > > > > accomplish you way. > > > > > > Use-case is to be able to use a pwm from a non-root userspace process. > > > I use udev rules to adjust permissions. > > > > Hmm, how do you trigger the export? Without being aware of all the > > details in the sysfs code I would expect that the exported stuff is > > available instantly once the write used to export the PWM is completed. > > So changing the permissions can be done directly after triggering the > > export in the same process. > > It looks like userspace wants to see when a pwmX device shows up, right? > > And it's not because those devices do not belong to any class or bus, so > they are just "floating" out there (they might show up under > /sys/bus/virtual, if you set things up right, which I don't think is > happening here...) > > So yes, you need to create a class, or assign this to a bus, which is > fine, but it looks like no one is doing that. Don't create new classes > dynamically, but rather, just assign this to the existing pwm class. > What's wrong with that? I saw an older patch that did that, what did > that break?
Are you refering to 7e5d1fd75c3dde9fc10c4472b9368089d1b81d00? Did you
read the reverting commit's log message? (i.e.
c289d6625237aa785b484b4e94c23b3b91ea7e60)
I guess the breakage is that the resulting name then is:
"pwm%d", pwm->id
where pwm->id is a number unique to the pwmchip. So doing
echo 0 > pwmchip1/export
echo 0 > pwmchip2/export
breaks because both want to create pwm0 in the class directory.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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