linux-kernel - Re: [PATCH] platform/x86: thinkpad_acpi: Fix registration of tpacpi platform driver

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Message-Id: <aee5fbe6-4309-450f-bea3-c0842172b043@app.fastmail.com>
Date: Sat, 08 Feb 2025 11:26:51 -0500
From: "Mark Pearson" <mpearson-lenovo@...ebb.ca>
To: "Kurt Borja" <kuurtb@...il.com>
Cc: "Hans de Goede" <hdegoede@...hat.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 "Limonciello, Mario" <mario.limonciello@....com>,
 "platform-driver-x86@...r.kernel.org" <platform-driver-x86@...r.kernel.org>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform/x86: thinkpad_acpi: Fix registration of tpacpi platform
 driver

Thanks Kurt,

On Fri, Feb 7, 2025, at 11:56 PM, Kurt Borja wrote:
> Hi Mark,
>
> On Sat Feb 8, 2025 at 4:14 AM -05, Mark Pearson wrote:
>> When reviewing and testing the recent platform profile changes I had
>> missed that they prevent the tpacpi platform driver from registering.
>> This error is seen in the kernel logs, and the various tpacpi entries
>> are not created:
>> [ 7550.642171] platform thinkpad_acpi: Resources present before probing
>
> This happens because in thinkpad_acpi_module_init(), ibm_init() is
> called before platform_driver_register(&tpacpi_pdriver), therefore
> devm_platform_profile_register() is called before tpacpi_pdev probes.
>
> As you can verify in [1], in the probing sequence, the driver core
> verifies the devres list is empty, which in this case is not because of
> the devm_ call.
>
>>
>> I believe this is because the platform_profile driver registers the
>> device as part of it's initialisation in devm_platform_profile_register,
>> and the thinkpad_acpi driver later fails as the resource is already used.
>>
>> Modified thinkpad_acpi so that it has a separate platform driver for the
>> profile handling, leaving the existing tpacpi_pdev to register
>> successfully.
>
> While this works, it does not address the problem directly. Also it is
> discouraged to create "fake" platform devices [2].
>
> May I suggest moving tpacpi_pdriver registration before ibm_init()
> instead, so ibm_init_struct's .init callbacks can use devres?
>

Yep - you're right. Moving it before the init does also fix it.

I can't see any issues with this approach, but I'll test it out a bit more carefully and do an updated version with this approach.

Thanks for the pointer.

Mark