net: phy: extend fixed driver with fixed_phy_register()

The existing fixed_phy_add() function has several drawbacks that
prevents it from being used as is for OF-based declaration of fixed
PHYs:

* The address of the PHY on the fake bus needs to be passed, while a
dynamic allocation is desired.

* Since the phy_device instantiation is post-poned until the next
mdiobus scan, there is no way to associate the fixed PHY with its
OF node, which later prevents of_phy_connect() from finding this
fixed PHY from a given OF node.

To solve this, this commit introduces fixed_phy_register(), which will
allocate an available PHY address, add the PHY using fixed_phy_add()
and instantiate the phy_device structure associated with the provided
OF node.

Signed-off-by: Thomas Petazzoni <[e-mail]>
Acked-by: Florian Fainelli <[e-mail]>
Acked-by: Grant Likely <[e-mail]>
Tested-by: Florian Fainelli <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/phy/fixed.c

···
 #include <linux/phy_fixed.h>
 #include <linux/err.h>
 #include <linux/slab.h>
+#include <linux/of.h>
 
 #define MII_REGS_NUM 29
 
···
 	return ret;
 }
 EXPORT_SYMBOL_GPL(fixed_phy_add);
+
+void fixed_phy_del(int phy_addr)
+{
+	struct fixed_mdio_bus *fmb = &platform_fmb;
+	struct fixed_phy *fp, *tmp;
+
+	list_for_each_entry_safe(fp, tmp, &fmb->phys, node) {
+		if (fp->addr == phy_addr) {
+			list_del(&fp->node);
+			kfree(fp);
+			return;
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(fixed_phy_del);
+
+static int phy_fixed_addr;
+static DEFINE_SPINLOCK(phy_fixed_addr_lock);
+
+int fixed_phy_register(unsigned int irq,
+		       struct fixed_phy_status *status,
+		       struct device_node *np)
+{
+	struct fixed_mdio_bus *fmb = &platform_fmb;
+	struct phy_device *phy;
+	int phy_addr;
+	int ret;
+
+	/* Get the next available PHY address, up to PHY_MAX_ADDR */
+	spin_lock(&phy_fixed_addr_lock);
+	if (phy_fixed_addr == PHY_MAX_ADDR) {
+		spin_unlock(&phy_fixed_addr_lock);
+		return -ENOSPC;
+	}
+	phy_addr = phy_fixed_addr++;
+	spin_unlock(&phy_fixed_addr_lock);
+
+	ret = fixed_phy_add(PHY_POLL, phy_addr, status);
+	if (ret < 0)
+		return ret;
+
+	phy = get_phy_device(fmb->mii_bus, phy_addr, false);
+	if (!phy || IS_ERR(phy)) {
+		fixed_phy_del(phy_addr);
+		return -EINVAL;
+	}
+
+	of_node_get(np);
+	phy->dev.of_node = np;
+
+	ret = phy_device_register(phy);
+	if (ret) {
+		phy_device_free(phy);
+		of_node_put(np);
+		fixed_phy_del(phy_addr);
+		return ret;
+	}
+
+	return 0;
+}
 
 static int __init fixed_mdio_bus_init(void)
 {

include/linux/phy_fixed.h

···
 	int asym_pause;
 };
 
+struct device_node;
+
 #ifdef CONFIG_FIXED_PHY
 extern int fixed_phy_add(unsigned int irq, int phy_id,
 			 struct fixed_phy_status *status);
+extern int fixed_phy_register(unsigned int irq,
+			      struct fixed_phy_status *status,
+			      struct device_node *np);
 #else
 static inline int fixed_phy_add(unsigned int irq, int phy_id,
 				struct fixed_phy_status *status)
+{
+	return -ENODEV;
+}
+static inline int fixed_phy_register(unsigned int irq,
+				     struct fixed_phy_status *status,
+				     struct device_node *np)
 {
 	return -ENODEV;
 }