linux-kernel - Re: [PATCH v3 2/2] hwmon: acpi_power_meter: convert to hwmon_device_register_with

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Message-ID: <YoHtg30ZrhxjVedA@Red>
Date:   Mon, 16 May 2022 08:21:55 +0200
From:   LABBE Corentin <clabbe@...libre.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     jdelvare@...e.com, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org, Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH v3 2/2] hwmon: acpi_power_meter: convert to
 hwmon_device_register_with_info

Le Sun, May 15, 2022 at 05:29:54PM -0700, Guenter Roeck a écrit :
> On 5/15/22 12:36, LABBE Corentin wrote:
> > Le Wed, May 11, 2022 at 07:10:29PM -0700, Guenter Roeck a écrit :
> >> Corentin,
> >>
> >> On 5/8/22 23:30, Corentin Labbe wrote:
> >>> Booting lead to a hwmon_device_register() is deprecated. Please convert the driver to use hwmon_device_register_with_info().
> >>> So let's convert the driver to use hwmon_device_register_with_info().
> >>>
> >>> Signed-off-by: Corentin Labbe <clabbe@...libre.com>
> >>> ---
> >> [ ... ]
> >>
> >>> @@ -836,20 +740,20 @@ static void acpi_power_meter_notify(struct acpi_device *device, u32 event)
> >>>    		if (res)
> >>>    			break;
> >>>    
> >>> -		remove_attrs(resource);
> >>> +		remove_domain_devices(resource);
> >>>    		setup_attrs(resource);
> >>
> >> Zhang Rui found an interesting problem with this code:
> >> It needs a call to sysfs_update_groups(hwmon_dev->groups)
> >> to update sysfs attribute visibility, probably between
> >> remove_domain_devices() and setup_attrs().
> >>
> >>>    		break;
> >>>    	case METER_NOTIFY_TRIP:
> >>> -		sysfs_notify(&device->dev.kobj, NULL, POWER_AVERAGE_NAME);
> >>> +		hwmon_notify_event(&device->dev, hwmon_power, hwmon_power_average, 0);
> >>
> >> ... which makes realize: The notification device should be the hwmon device.
> >> That would be resource->hwmon_dev, not the acpi device.
> >>
> > 
> > Hello
> > 
> > Since my hardware lacks capabilities testing this, I have emulated it on qemu:
> > https://github.com/montjoie/qemu/commit/320f2ddacb954ab308ef699f66fca6313f75bc2b
> > 
> > I have added a custom ACPI _DBX method for triggering some ACPI state change. (like config change, like enabling CAP).
> > 
> > For testing config change I have tried lot of way:
> >                  res = read_capabilities(resource);
> > @@ -742,18 +758,22 @@ static void acpi_power_meter_notify(struct acpi_device *device, u32 event)
> >   
> >                  remove_domain_devices(resource);
> >                  setup_attrs(resource);
> > +               res = sysfs_update_groups(&resource->hwmon_dev->kobj, acpi_power_groups);
> > +               res = sysfs_update_groups(&resource->acpi_dev->dev.kobj, acpi_power_groups);
> > +               res = hwmon_notify_event(resource->hwmon_dev, hwmon_power, hwmon_power_cap, 0);
> > +               res = hwmon_notify_event(resource->hwmon_dev, hwmon_power, hwmon_power_average, 0);
> 
> Did you add a debug log here ?

Yes I added debug log to check what is called.

> 
> acpi_power_groups would be the wrong parameter for sysfs_update_groups().
> It would have to be resource->hwmon_dev->groups.
> 

Even with that, no call to is_visible:
@@ -742,18 +758,22 @@ static void acpi_power_meter_notify(struct acpi_device *device, u32 event)
 
                remove_domain_devices(resource);
                setup_attrs(resource);
+               res = sysfs_update_groups(&resource->hwmon_dev->kobj, resource->hwmon_dev->groups);
+               res = sysfs_update_groups(&resource->acpi_dev->dev.kobj, resource->hwmon_dev->groups);
+               res = hwmon_notify_event(resource->hwmon_dev, hwmon_power, hwmon_power_cap, 0);
+               res = hwmon_notify_event(resource->hwmon_dev, hwmon_power, hwmon_power_average, 0);
                break;

I checked drivers/hwmon/hwmon.c is seems that is_visible is only called by gen_attr/gen_attrs which is only called by __hwmon_create_attrs and then by registers functions.
So perhaps it explain why it is never called.