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Sender: Guenter Roeck <groeck7@gmail.com>
Message-ID: <b2b3f17d-0f86-4d40-a471-f44153efd6fe@roeck-us.net>
Date:   Fri, 8 Dec 2023 07:43:07 -0800
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User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH] hwmon: (corsair-psu) Fix failure to load when built-in to
 kernel
Content-Language: en-US
To:     Wilken Gottwalt <wilken.gottwalt@posteo.net>,
        Aleksa Savic <savicaleksa83@gmail.com>
Cc:     linux-hwmon@vger.kernel.org, Jean Delvare <jdelvare@suse.com>,
        linux-kernel@vger.kernel.org, linux-input@vger.kernel.org,
        Jiri Kosina <jikos@kernel.org>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>
References: <20231208130710.191420-1-savicaleksa83@gmail.com>
 <d91d4bf1-3e8d-4b63-baa9-479a91d04eb7@gmail.com>
 <20231208145742.6def047a@posteo.net>
From:   Guenter Roeck <linux@roeck-us.net>
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In-Reply-To: <20231208145742.6def047a@posteo.net>
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On 12/8/23 05:57, Wilken Gottwalt wrote:
> On Fri, 8 Dec 2023 14:11:44 +0100
> Aleksa Savic <savicaleksa83@gmail.com> wrote:
> 
>> On 2023-12-08 14:07:10 GMT+01:00, Aleksa Savic wrote:
>>> When built-in to the kernel, the corsair-psu driver fails to register with
>>> the following message:
>>>
>>> "Driver 'corsair-psu' was unable to register with bus_type 'hid'
>>> because the bus was not initialized."
>>>
>>> Fix this by initializing the driver after the HID bus using
>>> late_initcall(), as hwmon is built before HID.
>>>
>>> Fixes: d115b51e0e56 ("hwmon: add Corsair PSU HID controller driver")
>>> Signed-off-by: Aleksa Savic <savicaleksa83@gmail.com>
>>> ---
>>>   drivers/hwmon/corsair-psu.c | 15 ++++++++++++++-
>>>   1 file changed, 14 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/hwmon/corsair-psu.c b/drivers/hwmon/corsair-psu.c
>>> index 904890598c11..48831a528965 100644
>>> --- a/drivers/hwmon/corsair-psu.c
>>> +++ b/drivers/hwmon/corsair-psu.c
>>> @@ -899,7 +899,20 @@ static struct hid_driver corsairpsu_driver = {
>>>   	.reset_resume	= corsairpsu_resume,
>>>   #endif
>>>   };
>>> -module_hid_driver(corsairpsu_driver);
>>> +
>>> +static int __init corsairpsu_hid_init(void)
>>> +{
>>> +	return hid_register_driver(&corsairpsu_driver);
>>> +}
>>> +
>>> +static void __exit corsairpsu_hid_exit(void)
>>> +{
>>> +	hid_unregister_driver(&corsairpsu_driver);
>>> +}
>>> +
>>> +/* When compiled into the kernel, initialize after the hid bus */
>>> +late_initcall(corsairpsu_hid_init);
>>> +module_exit(corsairpsu_hid_exit);
>>>   
>>>   MODULE_LICENSE("GPL");
>>>   MODULE_AUTHOR("Wilken Gottwalt <wilken.gottwalt@posteo.net>");
>>
>>
>> Woops! Just saw that the same fix was sent yesterday. Please disregard, sorry!
>>
>> Aleksa
> 
> It is fine. I just start to wonder if there was a change in the subsystem. I
> used the driver as built-in in the past for several months and never had that
> issue. And now it is a real flood of reports.
> 

Maybe there was a change in the build order, or some subtle change
in driver registration code. Question though is _when_ this changed.
It would be great if someone could bisect it. For example, bus registration
code has been changed significantly in v6.3. I am copying linux-input
and the hid maintainers for feedback.

Either case, I now have two patches and at least the first one was actually
tested, but no Reviewed-by: or Tested-by: for either of them. While that is
of course a formality, it would still be useful to show that it is not just
a random change.

Thanks,
Guenter