[PATCH v2] mux: mmio: depend on REGMAP as the code has that dependency

[Peter Rosin]

If CONFIG_REGMAP is not active, the build errors out like this:

../drivers/mux/mmio.c: In function ‘mux_mmio_probe’:
../drivers/mux/mmio.c:76:34: error: storage size of ‘field’ isn’t known
   76 |                 struct reg_field field;
      |                                  ^~~~~
In file included from ../include/linux/bits.h:21,
                 from ../include/linux/bitops.h:6,
                 from ../drivers/mux/mmio.c:8:
../include/linux/bits.h:23:28: error: first argument to ‘__builtin_choose_expr’ not a constant
   23 |         (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
      |                            ^~~~~~~~~~~~~~~~~~~~~
../include/linux/build_bug.h:16:62: note: in definition of macro ‘BUILD_BUG_ON_ZERO’
   16 | #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
      |                                                              ^
../include/linux/bits.h:37:10: note: in expansion of macro ‘GENMASK_INPUT_CHECK’
   37 |         (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
      |          ^~~~~~~~~~~~~~~~~~~
../drivers/mux/mmio.c:96:29: note: in expansion of macro ‘GENMASK’
   96 |                 if (mask != GENMASK(field.msb, field.lsb)) {
      |                             ^~~~~~~
../include/linux/build_bug.h:16:51: error: bit-field ‘<anonymous>’ width not an integer constant
   16 | #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
      |                                                   ^
../include/linux/bits.h:23:10: note: in expansion of macro ‘BUILD_BUG_ON_ZERO’
   23 |         (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
      |          ^~~~~~~~~~~~~~~~~
../include/linux/bits.h:37:10: note: in expansion of macro ‘GENMASK_INPUT_CHECK’
   37 |         (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
      |          ^~~~~~~~~~~~~~~~~~~
../drivers/mux/mmio.c:96:29: note: in expansion of macro ‘GENMASK’
   96 |                 if (mask != GENMASK(field.msb, field.lsb)) {
      |                             ^~~~~~~
../drivers/mux/mmio.c:102:29: error: implicit declaration of function ‘devm_regmap_field_alloc’ [-Werror=implicit-function-declaration]
  102 |                 fields[i] = devm_regmap_field_alloc(dev, regmap, field);
      |                             ^~~~~~~~~~~~~~~~~~~~~~~
../drivers/mux/mmio.c:76:34: warning: unused variable ‘field’ [-Wunused-variable]
   76 |                 struct reg_field field;
      |                                  ^~~~~

REGMAP is normally "selected", but that causes a recursive dependency.
But since REGMAP is "depended on" in other places, do so here as well.
The (implicit) REGMAP dependency was lost when the strict dependency
on MFD_SYSCON was removed.

Reported by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Fixes: 8ecfaca7926f ("mux: mmio: add generic regmap bitfield-based multiplexer")
Link: https://lore.kernel.org/lkml/64cf625b-2495-2382-0331-519d1cab0adf@xxxxxxxxxxxxx/
Signed-off-by: Peter Rosin <peda@xxxxxxxxxx>
---
 drivers/mux/Kconfig | 1 +
 1 file changed, 1 insertion(+)

Note, there is a patch in linux-next that removes "|| COMPILE_TEST" from the
pre-existing depends.

Cheers,
Peter

diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
index 80f015cf6e54..7f07ca06eb2b 100644
--- a/drivers/mux/Kconfig
+++ b/drivers/mux/Kconfig
@@ -48,6 +48,7 @@ config MUX_GPIO
 config MUX_MMIO
 	tristate "MMIO/Regmap register bitfield-controlled Multiplexer"
 	depends on OF
+	depends on REGMAP
 	help
 	  MMIO/Regmap register bitfield-controlled Multiplexer controller.
 
-- 
2.20.1