[PATCH v2] soundwire: Make slave.o depend on ACPI and rename to acpi_slave.o

[Nathan Chancellor <natechancellor@gmail.com>]

clang warns when CONFIG_ACPI is unset:

../drivers/soundwire/slave.c:16:12: warning: unused function
'sdw_slave_add' [-Wunused-function]
static int sdw_slave_add(struct sdw_bus *bus,
           ^
1 warning generated.

Before commit 8676b3ca4673 ("soundwire: fix regmap dependencies and
align with other serial links"), this code would only be compiled when
ACPI was set because it was only selected by SOUNDWIRE_INTEL, which
depends on ACPI.

Now, this code can be compiled without CONFIG_ACPI, which causes the
above warning. The IS_ENABLED(CONFIG_ACPI) guard could be moved to avoid
compiling the function; however, slave.c only contains three functions,
two of which are static. Since slave.c is completetely dependent on
ACPI, rename it to acpi_slave.c and only compile it when CONFIG_ACPI
is set so sdw_acpi_find_slaves will actually be used. bus.h contains
a stub for sdw_acpi_find_slaves so there will be no issues with an
undefined function.

This has been build tested with CONFIG_ACPI set and unset in combination
with CONFIG_SOUNDWIRE unset, built in, and a module.

Fixes: 8676b3ca4673 ("soundwire: fix regmap dependencies and align with other serial links")
Link: https://github.com/ClangBuiltLinux/linux/issues/637
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---

v1 -> v2:

* Rename slave.o to acpi_slave.o
* Reword commit message to reflect this

 drivers/soundwire/Makefile                  | 6 +++++-
 drivers/soundwire/{slave.c => acpi_slave.c} | 3 ---
 2 files changed, 5 insertions(+), 4 deletions(-)
 rename drivers/soundwire/{slave.c => acpi_slave.c} (98%)

diff --git a/drivers/soundwire/Makefile b/drivers/soundwire/Makefile
index 45b7e5001653..718d8dd0ac79 100644
--- a/drivers/soundwire/Makefile
+++ b/drivers/soundwire/Makefile
@@ -4,9 +4,13 @@
 #
 
 #Bus Objs
-soundwire-bus-objs := bus_type.o bus.o slave.o mipi_disco.o stream.o
+soundwire-bus-objs := bus_type.o bus.o mipi_disco.o stream.o
 obj-$(CONFIG_SOUNDWIRE) += soundwire-bus.o
 
+ifdef CONFIG_ACPI
+soundwire-bus-objs += acpi_slave.o
+endif
+
 #Cadence Objs
 soundwire-cadence-objs := cadence_master.o
 obj-$(CONFIG_SOUNDWIRE_CADENCE) += soundwire-cadence.o
diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/acpi_slave.c
similarity index 98%
rename from drivers/soundwire/slave.c
rename to drivers/soundwire/acpi_slave.c
index f39a5815e25d..0dc188e6873b 100644
--- a/drivers/soundwire/slave.c
+++ b/drivers/soundwire/acpi_slave.c
@@ -60,7 +60,6 @@ static int sdw_slave_add(struct sdw_bus *bus,
 	return ret;
 }
 
-#if IS_ENABLED(CONFIG_ACPI)
 /*
  * sdw_acpi_find_slaves() - Find Slave devices in Master ACPI node
  * @bus: SDW bus instance
@@ -110,5 +109,3 @@ int sdw_acpi_find_slaves(struct sdw_bus *bus)
 
 	return 0;
 }
-
-#endif
-- 
2.23.0.rc2