linux-kernel - Re: [PATCH v2 4/4] watchdog: jz4740: Make probe function __init_or

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Message-ID: <0dc0fd0a-54fc-5d70-af78-1874b5ece418@c-s.fr>
Date:   Sat, 8 Jun 2019 09:51:45 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Paul Cercueil <paul@...pouillou.net>,
        Guenter Roeck <linux@...ck-us.net>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>
Cc:     od@...c.me, linux-watchdog@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] watchdog: jz4740: Make probe function
 __init_or_module

Hi Paul,

Le 07/06/2019 à 18:24, Paul Cercueil a écrit :
> This allows the probe function to be dropped after the kernel finished
> its initialization, in the case where the driver was not compiled as a
> module.

I'm not sure that's what  __init_or_module flag does.

As far as I understand, this flag makes the function being dropped only 
when the kernel is built without modules support, ie without 
CONFIG_MODULES. See 
https://elixir.bootlin.com/linux/latest/source/include/linux/module.h#L145

In addition, I'm not sure you can simply define a probe function as 
__init. What if someone tries to unbind and rebind the device through 
sysfs for instance ?

It seems there is a special function called __platform_driver_probe() 
for registering devices when the probe function is to be in __init, see 
https://elixir.bootlin.com/linux/latest/source/drivers/base/platform.c#L684

Christophe

> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
> 
> Notes:
>      v2: New patch
> 
>   drivers/watchdog/jz4740_wdt.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/jz4740_wdt.c b/drivers/watchdog/jz4740_wdt.c
> index 7519d80c5d05..2061788c1939 100644
> --- a/drivers/watchdog/jz4740_wdt.c
> +++ b/drivers/watchdog/jz4740_wdt.c
> @@ -157,7 +157,7 @@ static const struct of_device_id jz4740_wdt_of_matches[] = {
>   MODULE_DEVICE_TABLE(of, jz4740_wdt_of_matches);
>   #endif
>   
> -static int jz4740_wdt_probe(struct platform_device *pdev)
> +static int __init_or_module jz4740_wdt_probe(struct platform_device *pdev)
>   {
>   	struct device *dev = &pdev->dev;
>   	struct jz4740_wdt_drvdata *drvdata;
>