Re: Calling device_init_wakeup() on driver removal

[Guenter Roeck]

On 01/15/2017 06:49 AM, Rafael J. Wysocki wrote:
> On Saturday, January 14, 2017 08:46:05 PM Guenter Roeck wrote:
> > Hi folks,
>
> Hi,
>
> > while looking through driver initialization and removal functions, I noticed that many drivers
> > call device_init_wakeup(dev, false) in the removal function. Given that the driver is about
> > to be removed, that doesn't make much sense to me, especially since device_wakeup_disable()
> > is called from device_pm_remove() anyway.
> >
> > Is it safe to assume that all those calls can be removed, or is there a possible reason for
> > keeping them around ?
>
> Removing them automatically might break things, because device_init_wakeup(dev, false)
> also clears the power.can_wakeup flag and removes the "wakeup" attribute from sysfs.

I had the same concern, but I concluded that the wakeup attribute should be removed
automatically, since it is added with sysfs_merge_group(), and the matching unmerge call
is also made in dpm_sysfs_remove(). power.can_wakeup is part of the device structure,
which is in the process of being removed, so I am not sure I understand how that can be
problematic.

> I guess they could be removed safely in the majority of cases, though.

How would one decide if it is needed ? I see some drivers call it on remove, but others
don't. I don't see a clear pattern; unless I am missing something, it seems to be
more or less random.

Thanks,
Guenter