linux-kernel - Re: [PATCH v2] hwmon: corsair-cpro: Change to HID driver

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Message-ID: <9fc09eec-7921-68ab-b3c7-1d83d3e09817@roeck-us.net>
Date:   Wed, 15 Jul 2020 12:49:59 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Marius Zachmann <mail@...iuszachmann.de>
Cc:     Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] hwmon: corsair-cpro: Change to HID driver

On 7/15/20 12:12 PM, Marius Zachmann wrote:
> On 15.07.20 at 17:35:08 CEST, Guenter Roeck wrote
>> On 7/15/20 8:14 AM, Marius Zachmann wrote:
>>> This changes corsair-cpro to a hid driver using hid reports.
>>>
>>> Signed-off-by: Marius Zachmann <mail@...iuszachmann.de>
>>>
>>> ---
>>
> ...
>>> -module_usb_driver(ccp_driver);
>>> +static int __init ccp_init(void)
>>> +{
>>> +	return hid_register_driver(&ccp_driver);
>>> +}
>>> +
>>> +static void __exit ccp_exit(void)
>>> +{
>>> +	hid_unregister_driver(&ccp_driver);
>>> +}
>>> +
>>> +/* make sure it is loaded after hid */
>>> +late_initcall(ccp_init);
>>> +module_exit(ccp_exit);
>>
>> Sorry for not noticing before, but can you use module_hid_driver() ?
>> That seems to work for other hid drivers.
>>
>> Thanks,
>> Guenter
>>
> 
> When using module_hid_driver() and compiling the driver as built-in
> the driver init function will get called before hid and fail registering
> the driver. late_initcall forces it to be loaded after hid.
> 

That seems odd. Why does no other hid driver have that problem ?
Your argument is pretty much that module_hid_driver() would not work,
which seems unlikely.

Thanks,
Guenter