Re: [PATCH] /dev/dax: fix Kconfig dependency build breakage

[Dan Williams]

On Fri, Sep 9, 2016 at 10:56 AM, Ross Zwisler
<ross.zwisler@xxxxxxxxxxxxxxx> wrote:
> The function dax_pmem_probe() in drivers/dax/pmem.c is compiled under the
> CONFIG_DEV_DAX_PMEM tri-state config option.  This config option currently
> only depends on CONFIG_NVDIMM_DAX, which means that the following
> configuration is possible:
>
> CONFIG_LIBNVDIMM=m
> ...
> CONFIG_NVDIMM_DAX=y
> CONFIG_DEV_DAX=y
> CONFIG_DEV_DAX_PMEM=y
>
> With this config LIBNVDIMM is compiled as a module with NVDIMM_DAX=y just
> meaning that we will compile drivers/nvdimm/dax_devs.c into that module.
> However, dax_pmem_probe() depends on several symbols defined in
> drivers/nvdimm/dax_devs.c, which results in the following build errors:
>
> drivers/built-in.o: In function `dax_pmem_probe':
> linux/drivers/dax/pmem.c:70: undefined reference to `to_nd_dax'
> linux/drivers/dax/pmem.c:74: undefined reference to `nvdimm_namespace_common_probe'
> linux/drivers/dax/pmem.c:80: undefined reference to `devm_nsio_enable'
> linux/drivers/dax/pmem.c:81: undefined reference to `nvdimm_setup_pfn'
> linux/drivers/dax/pmem.c:84: undefined reference to `devm_nsio_disable'
> linux/drivers/dax/pmem.c:122: undefined reference to `to_nd_region'
> drivers/built-in.o: In function `dax_pmem_init':
> linux/drivers/dax/pmem.c:147: undefined reference to `__nd_driver_register'
>
> Fix this by making CONFIG_DEV_DAX_PMEM explicitly depend on
> CONFIG_LIBNVDIMM.  This prevents dax_devs.c from being built as a built-in
> while its dependencies are in the libnvdimm.ko module.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> ---
>  drivers/dax/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
> index cedab75..5cd9436 100644
> --- a/drivers/dax/Kconfig
> +++ b/drivers/dax/Kconfig
> @@ -15,6 +15,7 @@ if DEV_DAX
>  config DEV_DAX_PMEM
>         tristate "PMEM DAX: direct access to persistent memory"
>         depends on NVDIMM_DAX
> +       depends on LIBNVDIMM

Hmm, NVDIMM_DAX already depends on LIBNVDIMM.  I think NVDIMM_DAX just
needs to be a tristate rather than a bool.