linux-kernel - Re: [PATCH v2 1/4] hwmon: (asus-ec-sensors) introduce ec_board

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Message-ID: <8a8579df-1fd6-32bb-3e27-297efefe28c4@roeck-us.net>
Date:   Wed, 27 Apr 2022 06:20:01 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Eugene Shalygin <eugene.shalygin@...il.com>
Cc:     Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/4] hwmon: (asus-ec-sensors) introduce ec_board_info
 struct for board data

On 4/27/22 05:16, Eugene Shalygin wrote:
>> Sorry, I don't follow that part. One can add "__init" or "__initdata",
>> as in
>>
>> static struct platform_driver asus_ec_sensors_platform_driver __initdata = {
>>
>> to mark a function or data structure as __init. I don't think adding
>> "_probe" to the struct platform_driver variable name does that.
>>
> 
> __initdata leads to modpost warning:
> WARNING: modpost: drivers/hwmon/asus-ec-sensors.o(.exit.text+0x3):
> Section mismatch in reference from the function cleanup_module() to
> the variable .init.data:asus_ec_sensors_platform_driver
> The function __exit cleanup_module() references
> a variable __initdata asus_ec_sensors_platform_driver.
> This is often seen when error handling in the exit function
> uses functionality in the init path.
> The fix is often to remove the __initdata annotation of
> asus_ec_sensors_platform_driver so it may be used outside an init section.
> 
> Compiling without attributes resulted in another message:
> WARNING: modpost: drivers/hwmon/asus-ec-sensors.o(.data+0x0): Section
> mismatch in reference from the variable
> asus_ec_sensors_platform_driver to the function
> .init.text:asus_ec_probe()
> The variable asus_ec_sensors_platform_driver references
> the function __init asus_ec_probe()
> If the reference is valid then annotate the
> variable with __init* or __refdata (see linux/init.h) or name the variable:
> *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console
> 
> Here is why I added the "_probe" suffix.
> 
> Eugene

Ah yes, I forgot about the exit function. It needs a pointer to
the structure, which would be gone if marked __initdata.
Please add a comment to the structure name explaining why
it is named _probe.

Thanks,
Guenter