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

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Date:   Sun, 15 May 2022 21:36:20 +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 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);
                break;
        case METER_NOTIFY_TRIP:
-               hwmon_notify_event(&device->dev, hwmon_power, hwmon_power_average, 0);
+               res = hwmon_notify_event(resource->hwmon_dev, hwmon_power, hwmon_power_average, 0);
                break;
        case METER_NOTIFY_CAP:
-               hwmon_notify_event(&device->dev, hwmon_power, hwmon_power_cap, 0);
+               res = hwmon_notify_event(resource->hwmon_dev, hwmon_power, hwmon_power_cap, 0);
                break;
        case METER_NOTIFY_INTERVAL:
-               hwmon_notify_event(&device->dev, hwmon_power, hwmon_power_average_interval, 0);
+               res = hwmon_notify_event(resource->hwmon_dev, hwmon_power, hwmon_power_average_interval, 0);
                break;
        case METER_NOTIFY_CAPPING:
-               hwmon_notify_event(&device->dev, hwmon_power, hwmon_power_alarm, 0);
+               res = hwmon_notify_event(resource->hwmon_dev, hwmon_power, hwmon_power_alarm, 0);
                dev_info(&device->dev, "Capping in progress.\n");
                break;
        default:

But nothing force visibility to be rerun.

Any idea on how to force visibility to be re-run ?