linux-kernel - Re: [PATCH v2 1/1] power: Emit changed uevent on wakeup_sysfs

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Date:   Tue, 7 Jul 2020 08:31:18 -0700
From:   Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Bluez mailing list <linux-bluetooth@...r.kernel.org>,
        ChromeOS Bluetooth Upstreaming 
        <chromeos-bluetooth-upstreaming@...omium.org>,
        rafael.j.wysocki@...el.com, Stephen Boyd <swboyd@...omium.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH v2 1/1] power: Emit changed uevent on wakeup_sysfs_add/remove

Hi Greg,


On Tue, Jul 7, 2020 at 7:29 AM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Mon, Jul 06, 2020 at 02:07:17PM -0700, Abhishek Pandit-Subedi wrote:
> > Udev rules that depend on the power/wakeup attribute don't get triggered
> > correctly if device_set_wakeup_capable is called after the device is
> > created. This can happen for several reasons (driver sets wakeup after
> > device is created, wakeup is changed on parent device, etc) and it seems
> > reasonable to emit a changed event when adding or removing attributes on
> > the device.
> >
> > Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
> > ---
> >
> > Changes in v2:
> > - Add newline at end of bt_dev_err
> >
> >  drivers/base/power/sysfs.c | 21 ++++++++++++++++++++-
> >  1 file changed, 20 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
> > index 24d25cf8ab1487..d57e8e7f175ebf 100644
> > --- a/drivers/base/power/sysfs.c
> > +++ b/drivers/base/power/sysfs.c
> > @@ -1,6 +1,7 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  /* sysfs entries for device PM */
> >  #include <linux/device.h>
> > +#include <linux/kobject.h>
> >  #include <linux/string.h>
> >  #include <linux/export.h>
> >  #include <linux/pm_qos.h>
> > @@ -739,12 +740,30 @@ int dpm_sysfs_change_owner(struct device *dev, kuid_t kuid, kgid_t kgid)
> >
> >  int wakeup_sysfs_add(struct device *dev)
> >  {
> > -     return sysfs_merge_group(&dev->kobj, &pm_wakeup_attr_group);
> > +     int ret = sysfs_merge_group(&dev->kobj, &pm_wakeup_attr_group);
> > +
> > +     if (!ret) {
> > +             int tmp = kobject_uevent(&dev->kobj, KOBJ_CHANGE);
> > +
> > +             if (tmp)
> > +                     dev_err(dev,
> > +                             "Error in uevent for wakeup_sysfs_add: %d\n",
> > +                             tmp);
> > +     }
> > +
> > +     return ret;
> >  }
>
> Shouldn't the above function look like this instead to be simpler:
>
> int wakeup_sysfs_add(struct device *dev)
> {
>         int ret = sysfs_merge_group(&dev->kobj, &pm_wakeup_attr_group);
>
>         if (ret)
>                 return ret;
>
>         return kobject_uevent(&dev->kobj, KOBJ_CHANGE);
> }
>
>
> >
> >  void wakeup_sysfs_remove(struct device *dev)
> >  {
> > +     int tmp;
>
> Use 'ret' like the above function had, to be consistent.
>
> > +
> >       sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group);
> > +
> > +     tmp = kobject_uevent(&dev->kobj, KOBJ_CHANGE);
> > +     if (tmp)
> > +             dev_err(dev, "Error in uevent for wakeup_sysfs_remove: %d\n",
>
> nit, use __func__ to describe a function name, if you really want it.
> Why do you need to send a message for this error, will that really ever
> happen?
>

Looking through kobject_uevent, it does look like the errors are
unlikely to be seen (-ENOMEM, -ENOENT) and probably don't need to be
logged.
Will apply the suggestions above and send a v3.

Thanks,
Abhishek

> thanks,
>
> greg k-h