Re: [PATCH v2] platform/x86: serial-multi-instantiate: Don't require both I2C and SPI

[Andy Shevchenko <andy.shevchenko@gmail.com>]

Wed, Aug 14, 2024 at 02:29:39PM +0100, Richard Fitzgerald kirjoitti:
> Change the Kconfig dependency so that it doesn't require both I2C and SPI
> subsystems to be built. Make a few small changes to the code so that the
> code for a bus is only called if the bus is being built.
> 
> When SPI support was added to serial-multi-instantiate it created a
> dependency that both CONFIG_I2C and CONFIG_SPI must be enabled.
> Typically they are, but there's no reason why this should be a
> requirement. A specific kernel build could have only I2C devices
> or only SPI devices. It should be possible to use serial-multi-instantiate
> if only I2C or only SPI is enabled.
> 
> The dependency formula used is:
> 
>   depends on (I2C && !SPI) || (!I2C && SPI) || (I2C && SPI)
> 
> The advantage of this approach is that if I2C=m or SPI=m then
> SERIAL_MULTI_INSTANTIATE is limited to n/m.

...

>  static void smi_devs_unregister(struct smi *smi)
>  {
> +#if IS_REACHABLE(CONFIG_I2C)

There is no explanation why ugly ifdeffery is used here, while normal
conditionals elsewhere.

>  	while (smi->i2c_num--)
>  		i2c_unregister_device(smi->i2c_devs[smi->i2c_num]);
> +#endif
>  
> -	while (smi->spi_num--)
> -		spi_unregister_device(smi->spi_devs[smi->spi_num]);
> +	if (IS_REACHABLE(CONFIG_SPI)) {
> +		while (smi->spi_num--)
> +			spi_unregister_device(smi->spi_devs[smi->spi_num]);
> +	}
>  }

There are ways to solve this:
1) add a stub for I2C=n for i2c_unregister_device();
2) resplit this driver to have several built modules:
   core, I2C parts, SPI parts.

-- 
With Best Regards,
Andy Shevchenko