Re: [PATCH v3 03/24] wfx: add Makefile/Kconfig

Jérôme Pouiller [off-list ref] writes:

On Tuesday 22 December 2020 16:02:38 CET Kalle Valo wrote:

quoted

Jerome Pouiller [off-list ref] writes:

quoted

From: Jérôme Pouiller <jerome.pouiller@silabs.com>

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>

[...]

quoted

+wfx-$(CONFIG_SPI) += bus_spi.o
+wfx-$(subst m,y,$(CONFIG_MMC)) += bus_sdio.o

Why this subst? And why only for MMC?

CONFIG_SPI is a boolean (y or empty). The both values make senses.

CONFIG_MMC is a tristate (y, m or empty). The substitution above
ensure that bus_sdio.o will included in wfx.ko if CONFIG_MMC is 'm'
("wfx-$(CONFIG_MMC) += bus_sdio.o" wouldn't make the job).

You may want to know what it happens if CONFIG_MMC=m while CONFIG_WFX=y.
This line in Kconfig prevents to compile wfx statically if MMC is a
module:
       depends on MMC || !MMC # do not allow WFX=y if MMC=m

Ok, thanks for explaining this.

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