netdev - [PATCH net-next v2 2/2] net: phy: fixed

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Message-ID: <d4614463-d532-41fc-92e9-ef97107aceb5@gmail.com>
Date: Sun, 11 Jan 2026 13:43:22 +0100
From: Heiner Kallweit <hkallweit1@...il.com>
To: Andrew Lunn <andrew@...n.ch>, Andrew Lunn <andrew+netdev@...n.ch>,
 Russell King - ARM Linux <linux@...linux.org.uk>,
 Paolo Abeni <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>,
 David Miller <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: [PATCH net-next v2 2/2] net: phy: fixed_phy: replace IDA with a
 bitmap

Size of array fmb_fixed_phys is small, so we can use a simple bitmap
instead of an IDA to manage dynamic allocation of fixed PHY's.
find_first_zero_bit() isn't atomic, so we need the loop to rule out
double allocation of a PHY address.

Suggested-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
---
v2:
- patch added
---
 drivers/net/phy/fixed_phy.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/drivers/net/phy/fixed_phy.c b/drivers/net/phy/fixed_phy.c
index 7d6078d1570..0b83fb30a54 100644
--- a/drivers/net/phy/fixed_phy.c
+++ b/drivers/net/phy/fixed_phy.c
@@ -16,7 +16,6 @@
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/of.h>
-#include <linux/idr.h>
 #include <linux/netdevice.h>
 
 #include "swphy.h"
@@ -32,13 +31,13 @@ struct fixed_phy {
 	int (*link_update)(struct net_device *, struct fixed_phy_status *);
 };
 
+static DECLARE_BITMAP(fixed_phy_ids, NUM_FP);
 static struct fixed_phy fmb_fixed_phys[NUM_FP];
 static struct mii_bus *fmb_mii_bus;
-static DEFINE_IDA(phy_fixed_ida);
 
 static struct fixed_phy *fixed_phy_find(int addr)
 {
-	return ida_exists(&phy_fixed_ida, addr) ? fmb_fixed_phys + addr : NULL;
+	return test_bit(addr, fixed_phy_ids) ? fmb_fixed_phys + addr : NULL;
 }
 
 int fixed_phy_change_carrier(struct net_device *dev, bool new_carrier)
@@ -113,7 +112,20 @@ static void fixed_phy_del(int phy_addr)
 		return;
 
 	memset(fp, 0, sizeof(*fp));
-	ida_free(&phy_fixed_ida, phy_addr);
+	clear_bit(phy_addr, fixed_phy_ids);
+}
+
+static int fixed_phy_get_free_addr(void)
+{
+	int addr;
+
+	do {
+		addr = find_first_zero_bit(fixed_phy_ids, NUM_FP);
+		if (addr == NUM_FP)
+			return -ENOSPC;
+	} while (test_and_set_bit(addr, fixed_phy_ids));
+
+	return addr;
 }
 
 struct phy_device *fixed_phy_register(const struct fixed_phy_status *status,
@@ -131,7 +143,7 @@ struct phy_device *fixed_phy_register(const struct fixed_phy_status *status,
 		return ERR_PTR(-EPROBE_DEFER);
 
 	/* Get the next available PHY address, up to NUM_FP */
-	phy_addr = ida_alloc_max(&phy_fixed_ida, NUM_FP - 1, GFP_KERNEL);
+	phy_addr = fixed_phy_get_free_addr();
 	if (phy_addr < 0)
 		return ERR_PTR(phy_addr);
 
@@ -210,8 +222,6 @@ static void __exit fixed_mdio_bus_exit(void)
 {
 	mdiobus_unregister(fmb_mii_bus);
 	mdiobus_free(fmb_mii_bus);
-
-	ida_destroy(&phy_fixed_ida);
 }
 module_exit(fixed_mdio_bus_exit);
 
-- 
2.52.0