net: phy: Allow splitting MDIO bus/device support from PHYs

Introduce a new configuration symbol: MDIO_DEVICE which allows building
the MDIO devices and bus code, without pulling in the entire Ethernet
PHY library and devices code.

PHYLIB nows select MDIO_DEVICE and the relevant Makefile files are
updated to reflect that.

When MDIO_DEVICE (MDIO bus/device only) is selected, but not PHYLIB, we
have mdio-bus.ko as a loadable module, and it does not have a
module_exit() function because the safety of removing a bus class is
unclear.

When both MDIO_DEVICE and PHYLIB are enabled, we need to assemble
everything into a common loadable module: libphy.ko because of nasty
circular dependencies between phy.c, phy_device.c and mdio_bus.c which
are really tough to untangle.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 56 insertions, 27 deletions

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index 7ab4b14a43b7..60ffc9da6a28 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -2,33 +2,12 @@
 # PHY Layer Configuration
 #
 
-menuconfig PHYLIB
-	tristate "PHY Device support and infrastructure"
-	depends on NETDEVICES
+menuconfig MDIO_DEVICE
+	tristate "MDIO bus device drivers"
 	help
-	  Ethernet controllers are usually attached to PHY
-	  devices.  This option provides infrastructure for
-	  managing PHY devices.
-
-if PHYLIB
-
-config SWPHY
-	bool
-
-config LED_TRIGGER_PHY
-	bool "Support LED triggers for tracking link state"
-	depends on LEDS_TRIGGERS
-	---help---
-	  Adds support for a set of LED trigger events per-PHY.  Link
-	  state change will trigger the events, for consumption by an
-	  LED class driver.  There are triggers for each link speed currently
-	  supported by the phy, and are of the form:
-	       <mii bus id>:<phy>:<speed>
-
-	  Where speed is in the form:
-		<Speed in megabits>Mbps or <Speed in gigabits>Gbps
+	   MDIO devices and driver infrastructure code.
 
-comment "MDIO bus device drivers"
+if MDIO_DEVICE
 
 config MDIO_BCM_IPROC
 	tristate "Broadcom iProc MDIO bus controller"
@@ -49,6 +28,7 @@ config MDIO_BCM_UNIMAC
 
 config MDIO_BITBANG
 	tristate "Bitbanged MDIO buses"
+	depends on !(MDIO_DEVICE=y && PHYLIB=m)
 	help
 	  This module implements the MDIO bus protocol in software,
 	  for use by low level drivers that export the ability to
@@ -160,6 +140,36 @@ config MDIO_XGENE
 	  This module provides a driver for the MDIO busses found in the
 	  APM X-Gene SoC's.
 
+endif
+
+menuconfig PHYLIB
+	tristate "PHY Device support and infrastructure"
+	depends on NETDEVICES
+	select MDIO_DEVICE
+	help
+	  Ethernet controllers are usually attached to PHY
+	  devices.  This option provides infrastructure for
+	  managing PHY devices.
+
+if PHYLIB
+
+config SWPHY
+	bool
+
+config LED_TRIGGER_PHY
+	bool "Support LED triggers for tracking link state"
+	depends on LEDS_TRIGGERS
+	---help---
+	  Adds support for a set of LED trigger events per-PHY.  Link
+	  state change will trigger the events, for consumption by an
+	  LED class driver.  There are triggers for each link speed currently
+	  supported by the phy, and are of the form:
+	       <mii bus id>:<phy>:<speed>
+
+	  Where speed is in the form:
+		<Speed in megabits>Mbps or <Speed in gigabits>Gbps
+
+
 comment "MII PHY device drivers"
 
 config AMD_PHY
diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index 82d915614646..0e1ec0438c23 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile
@@ -1,7 +1,16 @@
 # Makefile for Linux PHY drivers and MDIO bus drivers
 
-libphy-y			:= phy.o phy_device.o mdio_bus.o mdio_device.o \
-				   mdio-boardinfo.o phy-core.o
+libphy-y			:= phy.o phy-core.o phy_device.o
+mdio-bus-y			+= mdio_bus.o mdio_device.o mdio-boardinfo.o
+
+# PHYLIB implies MDIO_DEVICE, in that case, we have a bunch of circular
+# dependencies that does not make it possible to split mdio-bus objects into a
+# dedicated loadable module, so we bundle them all together into libphy.ko
+ifdef CONFIG_PHYLIB
+libphy-y			+= $(mdio-bus-y)
+else
+obj-$(CONFIG_MDIO_DEVICE)	+= mdio-bus.o
+endif
 libphy-$(CONFIG_SWPHY)		+= swphy.o
 libphy-$(CONFIG_LED_TRIGGER_PHY)	+= phy_led_triggers.o
 
diff --git a/drivers/net/phy/mdio-boardinfo.c b/drivers/net/phy/mdio-boardinfo.c
index 6b988f77da08..61941e29daae 100644
--- a/drivers/net/phy/mdio-boardinfo.c
+++ b/drivers/net/phy/mdio-boardinfo.c
@@ -84,3 +84,4 @@ int mdiobus_register_board_info(const struct mdio_board_info *info,
 
 	return 0;
 }
+EXPORT_SYMBOL(mdiobus_register_board_info);
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index fa7d51f14869..46b468eb6e12 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -648,9 +648,18 @@ int __init mdio_bus_init(void)
 
 	return ret;
 }
+EXPORT_SYMBOL_GPL(mdio_bus_init);
 
+#if IS_ENABLED(CONFIG_PHYLIB)
 void mdio_bus_exit(void)
 {
 	class_unregister(&mdio_bus_class);
 	bus_unregister(&mdio_bus_type);
 }
+EXPORT_SYMBOL_GPL(mdio_bus_exit);
+#else
+module_init(mdio_bus_init);
+/* no module_exit, intentional */
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("MDIO bus/device layer");
+#endif