Re: [PATCH] iio: light: vcnl4000: Don't create sysfs PM nodes for child

[Sudeep Holla <sudeep.holla@arm.com>]

On Mon, Nov 07, 2022 at 05:08:57PM +0000, Jonathan Cameron wrote:
> On Mon, 7 Nov 2022 10:36:36 +0000
> Sudeep Holla <sudeep.holla@arm.com> wrote:
> 
> > On Sun, Nov 06, 2022 at 03:23:07PM +0000, Jonathan Cameron wrote:
> > > On Tue, 1 Nov 2022 13:21:51 +0100
> > > Mårten Lindahl <marten.lindahl@axis.com> wrote:
> > >   
> > > > PM runtime is enabled for the parent i2c device, but it is disabled for
> > > > the iio child device and remains so in this driver. But as the child
> > > > sysfs PM directory is created by default by iio_device_register =>
> > > > cdev_device_add => dpm_sysfs_add it doesn't bring any value exposing it
> > > > since it won't give any usable data for the user.
> > > > 
> > > > Tell dpm_sysfs to not create the PM directory for the iio device.
> > > > 
> > > > Signed-off-by: Mårten Lindahl <marten.lindahl@axis.com>  
> > > 
> > > Ah this one..  +CC Sudeep who I am sure has considered such changes in other
> > > similar cases (he did the original ones that mean this infastructure exists).
> > >  
> > 
> > Yes it was added for cache devices which are child devices of CPU devices via
> > Commit 85945c28b5a8 ("PM / core: Add support to skip power management in device/driver model")
> > 
> > Since CPU and its children are power managed quite differently(via cpuidle
> > or cpu hotplug), the new API(device_set_pm_not_required) fits the usecase
> > there well. I am not sure about this IIO usecase.
> > 
> 
> These are effectively pseudo devices for purposes of the driver model, with parents
> as the actual physical devices. As such all the PM infrastructure is associate
> with the appropriate bus specific device rather than the struct iio_dev->dev.
>

Ah if there are psuedo devices or companion like devices, then yes I agree
worth not exposing the sysfs.

> So I'm fairly sure we should just not expose the sysfs attributes.

Agreed if it is psuedo device like you mention above.

> This is similar to CXL for which they are only exposed for the PCI devices, not
> the bunch of subdevices created.
> 

OK

-- 
Regards,
Sudeep