linux-kernel - Re: [PATCH] i3c: fix module_i3c_i2c

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Message-ID: <8cf89734-0663-4453-a079-8bdf40625746@roeck-us.net>
Date: Fri, 25 Jul 2025 02:19:19 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Arnd Bergmann <arnd@...nel.org>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>,
 Wolfram Sang <wsa+renesas@...g-engineering.com>,
 Boris Brezillon <bbrezillon@...nel.org>, Arnd Bergmann <arnd@...db.de>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Frank Li <Frank.Li@....com>, Geert Uytterhoeven
 <geert+renesas@...der.be>, linux-i3c@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i3c: fix module_i3c_i2c_driver() with I3C=n

On 7/25/25 02:06, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> When CONFIG_I3C is disabled and the i3c_i2c_driver_register() happens
> to not be inlined, any driver calling it still references the i3c_driver
> instance, which then causes a link failure:
> 
> x86_64-linux-ld: drivers/hwmon/lm75.o: in function `lm75_i3c_reg_read':
> lm75.c:(.text+0xc61): undefined reference to `i3cdev_to_dev'
> x86_64-linux-ld: lm75.c:(.text+0xd25): undefined reference to `i3c_device_do_priv_xfers'
> x86_64-linux-ld: lm75.c:(.text+0xdd8): undefined reference to `i3c_device_do_priv_xfers'
> 
> This issue was part of the original i3c code, but only now caused problems
> when i3c support got added to lm75.
> 
> Change the 'inline' annotations in the header to '__always_inline' to
> ensure that the dead-code-elimination pass in the compiler can optimize
> it out as intended.
> 
> Fixes: 6071d10413ff ("hwmon: (lm75) add I3C support for P3T1755")
> Fixes: 3a379bbcea0a ("i3c: Add core I3C infrastructure")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>   include/linux/i3c/device.h | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/i3c/device.h b/include/linux/i3c/device.h
> index b674f64d0822..7f136de4b73e 100644
> --- a/include/linux/i3c/device.h
> +++ b/include/linux/i3c/device.h
> @@ -245,7 +245,7 @@ void i3c_driver_unregister(struct i3c_driver *drv);
>    *
>    * Return: 0 if both registrations succeeds, a negative error code otherwise.
>    */
> -static inline int i3c_i2c_driver_register(struct i3c_driver *i3cdrv,
> +static __always_inline int i3c_i2c_driver_register(struct i3c_driver *i3cdrv,
>   					  struct i2c_driver *i2cdrv)
>   {
>   	int ret;
> @@ -270,7 +270,7 @@ static inline int i3c_i2c_driver_register(struct i3c_driver *i3cdrv,
>    * Note that when CONFIG_I3C is not enabled, this function only unregisters the
>    * @i2cdrv.
>    */
> -static inline void i3c_i2c_driver_unregister(struct i3c_driver *i3cdrv,
> +static __always_inline void i3c_i2c_driver_unregister(struct i3c_driver *i3cdrv,
>   					     struct i2c_driver *i2cdrv)
>   {
>   	if (IS_ENABLED(CONFIG_I3C))