On Thu, Jan 08, 2026 at 06:11:02PM -0800, Jakub Kicinski wrote:

On Tue, 6 Jan 2026 17:56:26 +0100 Heiner Kallweit wrote:

quoted

+/* The DSA loop driver may allocate 4 fixed PHY's, and 4 additional
+ * fixed PHY's for a system should be sufficient.
+ */
+#define NUM_FP	8
+
 struct fixed_phy {
-	int addr;
 	struct phy_device *phydev;
 	struct fixed_phy_status status;
 	int (*link_update)(struct net_device *, struct fixed_phy_status *);
-	struct list_head node;
 };
 
+static struct fixed_phy fmb_fixed_phys[NUM_FP];
 static struct mii_bus *fmb_mii_bus;
-static LIST_HEAD(fmb_phys);
+static DEFINE_IDA(phy_fixed_ida);

Isn't IDA an overkill for a range this tiny?
IDA is useful if the ID range is large and may be sparse.
Here a bitmap would suffice.

DECLARE_BITMAP(phy_fixed_ids, NUM_FP); 

id = find_first_zero_bit(phy_fixed_ids, NUM_FP);
if (id >= NUM_FP)
	return -ENOSPC;

set_bit(id, phy_fixed_ids);

Racy without locking.

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