> Another possibility would select this in _probe().
> We would need to evaluate mmc_can_gpio_cd() only once when probing.

I like this, too.

Maybe like this to be more obvious:

	if (mmc_can_gpio_cd(mmc))
		 _host->ops.get_cd = mmc_gpio_get_cd;
	else
		 _host->ops.get_cd = tmio...

?