linux-kernel - Re: [PATCH] thermal: core: Send a sysfs notification on trip points

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Date:   Mon, 6 Apr 2020 09:45:26 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
CC:     "rui.zhang@...el.com" <rui.zhang@...el.com>,
        "amit.kucheria@...durent.com" <amit.kucheria@...durent.com>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] thermal: core: Send a sysfs notification on trip points

On Fri, Apr 03, 2020 at 05:26:39PM +0200, Daniel Lezcano wrote:
> On 03/04/2020 16:40, Vincent Whitchurch wrote:
> > Normally sysfs_notify() is used to notify userspace that the value
> > of the sysfs file has changed, but in this case it's being used on
> > a sysfs file whose value never changes.  I don't know if there are
> > other drivers that do something similar.
> 
> I think so:
> 
> eg.
> 
> drivers/hwmon/adt7x10.c:
> 	sysfs_notify(&dev->kobj, NULL, "temp1_max_alarm");
> drivers/hwmon/adt7x10.c:
> 	sysfs_notify(&dev->kobj, NULL, "temp1_min_alarm");
> drivers/hwmon/adt7x10.c:
> 	sysfs_notify(&dev->kobj, NULL, "temp1_crit_alarm");
> 
> drivers/hwmon/abx500.c:
> 	sysfs_notify(&data->pdev->dev.kobj, NULL, alarm_node);
> drivers/hwmon/abx500.c:
> 	sysfs_notify(&data->pdev->dev.kobj, NULL, alarm_node);
> 
> drivers/hwmon/stts751.c:
> 	sysfs_notify(&priv->dev->kobj, NULL, "temp1_max_alarm");
> drivers/hwmon/stts751.c:
> 	sysfs_notify(&priv->dev->kobj, NULL, "temp1_min_alarm");
> 
> There are also some other places I believe they are doing the same like:
> 
> drivers/md/md.c:
> 	sysfs_notify(&mddev->kobj, NULL, "sync_completed");
> drivers/md/md.c:
> 	sysfs_notify(&mddev->kobj, NULL, "degraded");

AFAICS all these drivers (including the hwmon ones) use sysfs_notify()
to notify that the value of the sysfs file has changed, unlike your
proposed patch.