Re: [PATCH v2 1/1] power: Emit changed uevent on wakeup_sysfs_add/remove

From: Greg Kroah-Hartman
Date: Tue Jul 07 2020 - 10:29:03 EST


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@xxxxxxxxxxxx>
> ---
>
> 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