+/* Backplane custom logging */
+#define BPDEV_LOG(name) \
+	char log_buffer[LOG_BUFFER_SIZE]; \
+	va_list args; va_start(args, msg); \
+	vsnprintf(log_buffer, LOG_BUFFER_SIZE - 1, msg, args); \
+	if (!bpphy->attached_dev) \
+		dev_##name(&bpphy->mdio.dev, log_buffer); \
+	else \
+		dev_##name(&bpphy->mdio.dev, "%s: %s", \
+			netdev_name(bpphy->attached_dev), log_buffer); \
+	va_end(args)

+void bpdev_err(struct phy_device *bpphy, char *msg, ...)
+{
+	BPDEV_LOG(err);
+}
+EXPORT_SYMBOL(bpdev_err);
+
+void bpdev_warn(struct phy_device *bpphy, char *msg, ...)
+{
+	BPDEV_LOG(warn);
+}
+EXPORT_SYMBOL(bpdev_warn);
+
+void bpdev_info(struct phy_device *bpphy, char *msg, ...)
+{
+	BPDEV_LOG(info);
+}
+EXPORT_SYMBOL(bpdev_info);
+
+void bpdev_dbg(struct phy_device *bpphy, char *msg, ...)
+{
+	BPDEV_LOG(dbg);
+}
+EXPORT_SYMBOL(bpdev_dbg);

You are currently modelling this as a phydev. So please just use
phydev_err(), phydev_info(), phydev_dbg() etc.

Also, if you look at other PHY code, struct phy_device * is nearly
always called phydev. Please try to be consistent with the existing
code base.

     Andrew