netdev - [PATCH net-next] mdio, phy: fix -Wshadow warnings triggered by nested container

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Date:   Sat, 16 Jan 2021 16:13:22 +0000
From:   Alexander Lobakin <alobakin@...me>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Alexander Lobakin <alobakin@...me>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH net-next] mdio, phy: fix -Wshadow warnings triggered by nested container_of()

container_of() macro hides a local variable '__mptr' inside. This
becomes a problem when several container_of() are nested in each
other within single line or plain macros.
As C preprocessor doesn't support generating random variable names,
the sole solution is to avoid defining macros that consist only of
container_of() calls, or they will self-shadow '__mptr' each time:

In file included from ./include/linux/bitmap.h:10,
                 from drivers/net/phy/phy_device.c:12:
drivers/net/phy/phy_device.c: In function ‘phy_device_release’:
./include/linux/kernel.h:693:8: warning: declaration of ‘__mptr’ shadows a previous local [-Wshadow]
  693 |  void *__mptr = (void *)(ptr);     \
      |        ^~~~~~
./include/linux/phy.h:647:26: note: in expansion of macro ‘container_of’
  647 | #define to_phy_device(d) container_of(to_mdio_device(d), \
      |                          ^~~~~~~~~~~~
./include/linux/mdio.h:52:27: note: in expansion of macro ‘container_of’
   52 | #define to_mdio_device(d) container_of(d, struct mdio_device, dev)
      |                           ^~~~~~~~~~~~
./include/linux/phy.h:647:39: note: in expansion of macro ‘to_mdio_device’
  647 | #define to_phy_device(d) container_of(to_mdio_device(d), \
      |                                       ^~~~~~~~~~~~~~
drivers/net/phy/phy_device.c:217:8: note: in expansion of macro ‘to_phy_device’
  217 |  kfree(to_phy_device(dev));
      |        ^~~~~~~~~~~~~
./include/linux/kernel.h:693:8: note: shadowed declaration is here
  693 |  void *__mptr = (void *)(ptr);     \
      |        ^~~~~~
./include/linux/phy.h:647:26: note: in expansion of macro ‘container_of’
  647 | #define to_phy_device(d) container_of(to_mdio_device(d), \
      |                          ^~~~~~~~~~~~
drivers/net/phy/phy_device.c:217:8: note: in expansion of macro ‘to_phy_device’
  217 |  kfree(to_phy_device(dev));
      |        ^~~~~~~~~~~~~

As they are declared in header files, these warnings are highly
repetitive and very annoying (along with the one from linux/pci.h).

Convert the related macros from linux/{mdio,phy}.h to static inlines
to avoid self-shadowing and potentially improve bug-catching.
No functional changes implied.

Signed-off-by: Alexander Lobakin <alobakin@...me>
---
 include/linux/mdio.h | 23 ++++++++++++++++++-----
 include/linux/phy.h  |  7 +++++--
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/include/linux/mdio.h b/include/linux/mdio.h
index dbd69b3d170b..ffb787d5ebde 100644
--- a/include/linux/mdio.h
+++ b/include/linux/mdio.h
@@ -49,7 +49,11 @@ struct mdio_device {
 	unsigned int reset_assert_delay;
 	unsigned int reset_deassert_delay;
 };
-#define to_mdio_device(d) container_of(d, struct mdio_device, dev)
+
+static inline struct mdio_device *to_mdio_device(const struct device *dev)
+{
+	return container_of(dev, struct mdio_device, dev);
+}
 
 /* struct mdio_driver_common: Common to all MDIO drivers */
 struct mdio_driver_common {
@@ -57,8 +61,12 @@ struct mdio_driver_common {
 	int flags;
 };
 #define MDIO_DEVICE_FLAG_PHY		1
-#define to_mdio_common_driver(d) \
-	container_of(d, struct mdio_driver_common, driver)
+
+static inline struct mdio_driver_common *
+to_mdio_common_driver(const struct device_driver *driver)
+{
+	return container_of(driver, struct mdio_driver_common, driver);
+}
 
 /* struct mdio_driver: Generic MDIO driver */
 struct mdio_driver {
@@ -73,8 +81,13 @@ struct mdio_driver {
 	/* Clears up any memory if needed */
 	void (*remove)(struct mdio_device *mdiodev);
 };
-#define to_mdio_driver(d)						\
-	container_of(to_mdio_common_driver(d), struct mdio_driver, mdiodrv)
+
+static inline struct mdio_driver *
+to_mdio_driver(const struct device_driver *driver)
+{
+	return container_of(to_mdio_common_driver(driver), struct mdio_driver,
+			    mdiodrv);
+}
 
 /* device driver data */
 static inline void mdiodev_set_drvdata(struct mdio_device *mdio, void *data)
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 24fcc6456a9e..bc323fbdd21e 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -648,8 +648,11 @@ struct phy_device {
 	const struct macsec_ops *macsec_ops;
 #endif
 };
-#define to_phy_device(d) container_of(to_mdio_device(d), \
-				      struct phy_device, mdio)
+
+static inline struct phy_device *to_phy_device(const struct device *dev)
+{
+	return container_of(to_mdio_device(dev), struct phy_device, mdio);
+}
 
 /**
  * struct phy_tdr_config - Configuration of a TDR raw test
-- 
2.30.0