Re: [PATCH v4 1/1] power: Emit changed uevent on wakeup_sysfs_add/remove

[Rafael J. Wysocki]

On Tue, Jul 7, 2020 at 6:24 PM Abhishek Pandit-Subedi
<abhishekpandit@xxxxxxxxxxxx> 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@xxxxxxxxxxxx>
> ---
>
> Changes in v4:
> - Fix warning where returning from void and tested on device
>
> Changes in v3:
> - Simplified error handling
>
> Changes in v2:
> - Add newline at end of bt_dev_err
>
>  drivers/base/power/sysfs.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
> index 24d25cf8ab1487..aeb58d40aac8de 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 +740,18 @@ 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)
> +               return ret;
> +
> +       return kobject_uevent(&dev->kobj, KOBJ_CHANGE);

So let me repeat the previous comment:

If you return an error here, it may confuse the caller to think that
the operation has failed completely, whereas the merging of the
attribute group has been successful already.

I don't think that an error can be returned at this point.

>  }
>
>  void wakeup_sysfs_remove(struct device *dev)
>  {
>         sysfs_unmerge_group(&dev->kobj, &pm_wakeup_attr_group);
> +       kobject_uevent(&dev->kobj, KOBJ_CHANGE);
>  }
>
>  int pm_qos_sysfs_add_resume_latency(struct device *dev)
> --
> 2.27.0.212.ge8ba1cc988-goog
>