linux-kernel - Re: [PATCH] platform/x86: wmi: Initialize ACPI device class

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Date: Tue, 30 Jan 2024 03:10:13 +0100
From: Armin Wolf <W_Armin@....de>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
 Hans de Goede <hdegoede@...hat.com>
Cc: ilpo.jarvinen@...ux.intel.com, platform-driver-x86@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform/x86: wmi: Initialize ACPI device class

Am 29.01.24 um 14:08 schrieb Rafael J. Wysocki:

> On Mon, Jan 29, 2024 at 1:51 PM Hans de Goede <hdegoede@...hat.com> wrote:
>> Hi,
>>
>> On 1/24/24 20:07, Armin Wolf wrote:
>>> When an ACPI netlink event is received by acpid, the ACPI device
>>> class is passed as its first argument. But since the class string
>>> is not initialized, an empty string is being passed:
>>>
>>>        netlink:  PNP0C14:01 000000d0 00000000
>>>
>>> Fix this by initializing the ACPI device class during probe.
>>>
>>> Signed-off-by: Armin Wolf <W_Armin@....de>
>>> ---
>>> Note: This patch is based on commit 3f399b5d7189 ("platform/x86: wmi: Use ACPI device name in netlink event")
>>> ---
>>>   drivers/platform/x86/wmi.c | 6 +++++-
>>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
>>> index 7ef1e82dc61c..b92425c30a50 100644
>>> --- a/drivers/platform/x86/wmi.c
>>> +++ b/drivers/platform/x86/wmi.c
>>> @@ -32,6 +32,8 @@
>>>   #include <linux/wmi.h>
>>>   #include <linux/fs.h>
>>>
>>> +#define ACPI_WMI_DEVICE_CLASS        "wmi"
>>> +
>>>   MODULE_AUTHOR("Carlos Corbacho");
>>>   MODULE_DESCRIPTION("ACPI-WMI Mapping Driver");
>>>   MODULE_LICENSE("GPL");
>>> @@ -1202,7 +1204,7 @@ static int wmi_notify_device(struct device *dev, void *data)
>>>                wblock->handler(*event, wblock->handler_data);
>>>        }
>>>
>>> -     acpi_bus_generate_netlink_event(wblock->acpi_device->pnp.device_class,
>>> +     acpi_bus_generate_netlink_event(acpi_device_class(wblock->acpi_device),
>>>                                        acpi_dev_name(wblock->acpi_device), *event, 0);
>>>
>>>        return -EBUSY;
>>> @@ -1267,6 +1269,8 @@ static int acpi_wmi_probe(struct platform_device *device)
>>>                return -ENODEV;
>>>        }
>>>
>>> +     strscpy(acpi_device_class(acpi_device), ACPI_WMI_DEVICE_CLASS, sizeof(acpi_device_class));
>>> +
>> Hmm, I'm not sure if you are supposed to do this when you are not an
>> acpi_driver's add() function.
> You aren't.

I believed otherwise, as the ACPI AC driver (which is a platform_driver) does the same thing.
Seems i was wrong on that.

>
>> Rafael, do you have any comments on this ?
> I'm not quite sure why this is done here.

The initialization of the ACPI device class is being done to access this value later when sending an
ACPI netlink event like other ACPI drivers do.

However since you clarified that doing this outside of an acpi_driver's add() function is forbidden
i think it would indeed be better to just pass the value directly without touching the ACPI device class.

Thanks,
Armin Wolf