Re: [PATCH net-next] net: phy: fixed_phy: replace list of fixed PHYs with static array

[Heiner Kallweit <hkallweit1@gmail.com>]

On 1/9/2026 3:11 AM, Jakub Kicinski wrote:
> On Tue, 6 Jan 2026 17:56:26 +0100 Heiner Kallweit wrote:
>> +/* 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.
> 

Thanks for the suggestion! The IDA has been there forever, just the definition
has been moved now. I think switching to a bitmap is a good option.
Can we handle this as a follow-up?

> 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);
> ...