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

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Date:   Thu, 30 Jun 2022 08:13:24 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     LABBE Corentin <clabbe@...libre.com>
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

On 6/30/22 07:49, LABBE Corentin wrote:
> Le Sat, May 21, 2022 at 06:52:15AM -0700, Guenter Roeck a écrit :
>> On 5/16/22 05:21, Guenter Roeck wrote:
>>> On 5/15/22 23:21, LABBE Corentin wrote:
>>>> 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.
>>>
>>> Ah yes, you are correct. Sorry, it has been too long ago that I wrote that code.
>>> Effectively that means we'll have to rework the hwmon core to generate attributes
>>> anyway and leave it up to the driver core to call the is_visible function.
>>>
>>
>> Attached is an outline of what would be needed in the hwmon core.
>> Completely untested. I wonder if it may be easier to always
>> create all attributes and have them return -ENODATA if not
>> supported.
>>
>> Guenter
> 
> 
> Hello
> 
> Do you plan to send your change as patch ?
> My patch serie is stuck since now it depend on it.
> 
> Or can I send a new iteration of my serie with partial support for notify.
> 

Unfortunately I won't have time to work on this anytime soon.

Guenter