linux-kernel - Re: [PATCH v7 00/14] platform/x86: alienware-wmi driver rework

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Message-Id: <D7ISQ5PQLOLR.2P6D3M7W54PA3@gmail.com>
Date: Mon, 03 Feb 2025 07:06:19 -0500
From: "Kurt Borja" <kuurtb@...il.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: <platform-driver-x86@...r.kernel.org>, "Armin Wolf" <W_Armin@....de>,
 "Mario Limonciello" <mario.limonciello@....com>, "Hans de Goede"
 <hdegoede@...hat.com>, <Dell.Client.Kernel@...l.com>, "LKML"
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 00/14] platform/x86: alienware-wmi driver rework

On Mon Feb 3, 2025 at 4:20 AM -05, Ilpo Järvinen wrote:
> On Mon, 3 Feb 2025, Kurt Borja wrote:
>
>> Hi!
>>
>> I bring some last minute modifications.
>> 
>> I found commit
>> 
>> 	8d8fc146dd7a ("nvmem: core: switch to use device_add_groups()")
>> 
>> which states that it's unnecesary to call device_remove_groups() when
>> the device is removed, so I dropped it to simplify things.
>
> Hi Kurt,

Hi Ilpo,

>
>> I also found commit
>> 
>> 	957961b6dcc8 ("hwmon: (oxp-sensors) Move tt_toggle attribute to dev_groups")
>> 
>> which states that no driver should add sysfs groups while probing the
>> device as it races with userspace, so I re-added PROBE_FORCE_SYNCHRONOUS
>> to the platform driver, so groups are added only after the device has
>> finished probing.
>>
>> I'm not 100% sure that the second commit message applies here, but it is
>> revd-by Greg K-H so I added it just in case.
>
> Which is why .dev_groups should be used as it is able to avoid those 
> races on driver core level.

In previous discussions with Armin we agreed it made more sense to move
WMAX-only groups from alienware-wmi-base.c to alienware-wmi-wmax.c when
splitting.

I have no problem in moving them back to .dev_groups though.

>
> Why you call device_add_groups() at all? Can't you just insert it into 
> .dev_groups member in alienware_wmax_wmi_driver?

I'd love to do this as it would simplify things a LOT, but some
user-space tools might expect this attributes to be exposed by the
"fake" platform device located at

/sys/devices/platform/alienware-wmi

If it were not for this, I would expose every attribute in the WMI
device.

~ Kurt