[PATCH v2] /dev/dax: fix Kconfig dependency build breakage

From: Ross Zwisler
Date: Mon Sep 12 2016 - 12:15:21 EST

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, a bool, which means that the following
configuration is possible:


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
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 NVDIMM_DAX a tristate. DEV_DAX_PMEM depends on
NVDIMM_DAX which depends on LIBNVDIMM. Since they are all now tristates,
if LIBNVDIMM is built as a kernel module DEV_DAX_PMEM will be as well.
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>
Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx>

Change from v1:
- Made NVDIMM_DAX a tristate instead of adding an extra dependency. (djbw)

drivers/nvdimm/Kconfig | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvdimm/Kconfig b/drivers/nvdimm/Kconfig
index 124c243..8b2b740 100644
--- a/drivers/nvdimm/Kconfig
+++ b/drivers/nvdimm/Kconfig
@@ -89,7 +89,7 @@ config NVDIMM_PFN
Select Y if unsure

- bool "NVDIMM DAX: Raw access to persistent memory"
+ tristate "NVDIMM DAX: Raw access to persistent memory"
depends on NVDIMM_PFN