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Date: Wed, 2 Feb 2022 18:35:00 +0100
From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Mark Brown <broonie@kernel.org>
Cc: kernel test robot <lkp@intel.com>, llvm@lists.linux.dev,
 kbuild-all@lists.01.org, linux-kernel@vger.kernel.org
Subject: Re: [mtd:spi-mem-ecc 30/30] ld.lld: error: undefined symbol:
 nand_ecc_unregister_on_host_hw_engine
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Hi Mark,

broonie@kernel.org wrote on Wed, 2 Feb 2022 16:15:35 +0000:

> On Wed, Feb 02, 2022 at 04:34:52PM +0100, Miquel Raynal wrote:
> > > On Wed, Feb 02, 2022 at 03:45:04PM +0100, Miquel Raynal wrote: =20
>=20
> > > > I've failed to prevent faulty configurations with regular depends
> > > > on/select keywords, so I've come with a new solution which received=
 a
> > > > successful build coverage test from the 0-day robots.   =20
>=20
> > > > In order to still be able to use the spi controller driver (=3Dy) w=
hile
> > > > mtd is =3Dm or =3Dn, I need to add an IS_REACHABLE() check in a cou=
ple of
> > > > headers. This way we can just imply the right MTD symbols from the
> > > > SPI_MXIC Kconfig entry.   =20
>=20
> > > Isn't this just a case where we shouldn't allow MTD to be built modul=
ar? =20
>=20
> > How would you do that in a nice Kconfig way? =20
>=20
> depends on MTD=3Dy if SPI_MXC=3Dy

In this case I believe we should also add

depends on MTD=3Dm if SPI_MXC=3Dm ?

Anyway, this would force building the ECC support (and MTD...) even
though we don't need it in most cases.

My idea was to give people the right to only select SPI_MXIC without
really caring about MTD/ECC support at all because this is IMHO a
valid use case. We would then save a few kiB of extra MTD fat.

What do you think?

Thanks,
Miqu=C3=A8l