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

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Date:   Tue, 7 Jul 2020 16:28:59 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
Cc:     linux-pm@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        chromeos-bluetooth-upstreaming@...omium.org,
        rafael.j.wysocki@...el.com, swboyd@...omium.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        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

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?

thanks,

greg k-h