Re: [PATCH v3] net: dsa: rtl8366rb: Fix compilation problem

[Vladimir Oltean <olteanv@gmail.com>]

On Thu, Feb 20, 2025 at 07:48:15PM +0100, Linus Walleij wrote:
> When the kernel is compiled without LED framework support the
> rtl8366rb fails to build like this:
> 
> rtl8366rb.o: in function `rtl8366rb_setup_led':
> rtl8366rb.c:953:(.text.unlikely.rtl8366rb_setup_led+0xe8):
>   undefined reference to `led_init_default_state_get'
> rtl8366rb.c:980:(.text.unlikely.rtl8366rb_setup_led+0x240):
>   undefined reference to `devm_led_classdev_register_ext'
> 
> As this is constantly coming up in different randconfig builds,
> bite the bullet and create a separate file for the offending
> code, split out a header with all stuff needed both in the
> core driver and the leds code.
> 
> Add a new bool Kconfig option for the LED compile target, such
> that it depends on LEDS_CLASS=y || LEDS_CLASS=RTL8366RB
> which make LED support always available when LEDS_CLASS is
> compiled into the kernel and enforce that if the LEDS_CLASS
> is a module, then the RTL8366RB driver needs to be a module
> as well so that modprobe can resolve the dependencies.
> 
> Fixes: 32d617005475 ("net: dsa: realtek: add LED drivers for rtl8366rb")
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202502070525.xMUImayb-lkp@intel.com/
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> Changes in v3:
> - Create a new NET_DSA_REALTEK_RTL8366RB_LEDS symbol and make
>   it resolve the compiled-in vs compiled-as-module dependencies.
> - Link to v2: https://lore.kernel.org/r/20250220-rtl8366rb-leds-compile-issue-v2-1-8f8ef5a3f022@linaro.org

The Kconfig approach where NET_DSA_REALTEK_RTL8366RB_LEDS just
disappears when there is a mismatch between LEDS_CLASS and RTL8366RB is
a bit unusual to me (I'm used to just seeing "depends on LEDS_CLASS || LEDS_CLASS=n"),
but this seems to work too, as far as I can see.

Reviewed-by: Vladimir Oltean <olteanv@gmail.com>