linux-kernel - Re: [PATCH] mcb: Fix incorrect sanity check

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Message-ID: <97cab4b5-ab35-4cbe-a8ee-8ad6ea522159@gmail.com>
Date: Fri, 16 Jan 2026 11:33:02 +0100
From: Johannes Thumshirn <morbidrsa@...il.com>
To: Jose Javier Rodriguez Barbarin <dev-josejavier.rodriguez@...gon.com>
Cc: gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mcb: Fix incorrect sanity check

On 1/16/26 11:30 AM, Jose Javier Rodriguez Barbarin wrote:
> On Fri, Nov 21, 2025 at 11:54:08AM +0100, Johannes Thumshirn wrote:
>> On 11/21/25 11:33 AM, Jose Javier Rodriguez Barbarin wrote:
>>> On Thu, Nov 20, 2025 at 12:48:45PM +0100, Johannes Thumshirn wrote:
>>>> On 11/20/25 12:37 PM, Jose Javier Rodriguez Barbarin wrote:
>>>>> __mcb_register_driver() makes some sanity checks over mcb_driver
>>>>> to check if .probe and .remove callbacks are set. However, not all
>>>>> mcb device drivers implement .remove callback.
>>>>>
>>>>> Remove .remove check to ensure all mcb device drivers can be loaded.
>>>> The only driver I can see that doesn't implement a .remove method is
>>>> gpio-menz127.c.
>>> Yes. In the past gpio-menz127.c also implemented .remove method, however in
>>>
>>> 3bd13ae04ccc ("gpio: menz127: simplify error path and remove remove()")
>>>
>>> The driver changed, using now devm_* functions so .remove was no longer necessary.
>>>
>>>> Is this safe?
>>>>
>>>   From the point of view of mcb bus it should be safe becase I protected the call
>>> of .remove on mcb_remove(), preventing possible crashes when the driver is removed
>>> from the bus.
>>>
>>> I'm afraid I'm lossing something because I cannot understand why these changes are or
>>> not safe. Could you explain me why you understand that these changes are unsafe?
>>
>> Thanks this is the information I was missing from the changelog. I'll change
>> the commit message to:
>>
>> __mcb_register_driver() makes some sanity checks over mcb_driver
>> to check if .probe and .remove callbacks are set. However, since commit
>> 3bd13ae04ccc ("gpio: menz127: simplify error path and remove remove()")
>> removed the .remove callback from menz127-gpio.c, not all mcb device
>> drivers implement .remove callback.
>>
>> Remove .remove check to ensure all mcb device drivers can be loaded.
>>
>> I'll also add
>>
>> Fixes: 3bd13ae04ccc ("gpio: menz127: simplify error path and remove remove()")
>>
>>
>> Thanks,
>>
>>      Johannes
>>
> Hi Johannes,
>
> I noticed this patch is not uploaded yet.
>
> I can submit it again changing the commit message as you commented above.
>
> Thank you,
>
> Javier R.

Yes I wanted to forward it to Greg and then I forgot I'm sorry. But I 
think it's still in time for v6.20. I'll do so ASAP.