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Calling device_init_wakeup() on driver removal

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  Calling device_init_wakeup() on driver removal Guenter Roeck <linux@roeck-us.net> - 2017-01-15 05:50 +0100
    Re: Calling device_init_wakeup() on driver removal "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-01-15 16:00 +0100
      Re: Calling device_init_wakeup() on driver removal Guenter Roeck <linux@roeck-us.net> - 2017-01-15 16:30 +0100

#1559160 — Calling device_init_wakeup() on driver removal

Hi folks,

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 ?

Thanks,
Guenter

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#1559250

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

Thanks,
Rafael

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#1559273

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

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