linux-kernel - Re: [PATCH] hwmon: (corsair-psu) Fix failure to load when built-in to kernel

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Message-ID: <fe16b501-759a-492b-9835-83ebf8761ae8@gmail.com>
Date:   Fri, 8 Dec 2023 17:52:47 +0100
From:   Aleksa Savic <savicaleksa83@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        Wilken Gottwalt <wilken.gottwalt@...teo.net>
Cc:     savicaleksa83@...il.com, linux-hwmon@...r.kernel.org,
        Jean Delvare <jdelvare@...e.com>, linux-kernel@...r.kernel.org,
        linux-input@...r.kernel.org, Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>
Subject: Re: [PATCH] hwmon: (corsair-psu) Fix failure to load when built-in to
 kernel

On 2023-12-08 16:43:07 GMT+01:00, Guenter Roeck wrote:
> On 12/8/23 05:57, Wilken Gottwalt wrote:
>> On Fri, 8 Dec 2023 14:11:44 +0100
>> Aleksa Savic <savicaleksa83@...il.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@...il.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@...teo.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.

The late_initcall() was also needed in 2020. when corsair-cpro was added in
40c3a4454225 ("hwmon: add Corsair Commander Pro driver").

There was also discussion on the list about it:

https://lore.kernel.org/all/3864498.z6qT3ff8q6@marius/

nzxt-smart2 (from the tail of 2021.) also has a comment about the message.

(Just providing references.)

Aleksa

> 
> 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
>