Re: [PATCH v4 12/12] NTB: epf: Implement db_vector_count/mask for doorbells

[Dave Jiang]

On 5/12/26 7:49 PM, Koichiro Den wrote:
> Implement .db_vector_count and .db_vector_mask so ntb core/clients can
> map doorbell events to per-vector work.
> 
> Report vectors as 0..(db_count - 2) (skipping the unused slot) and return
> BIT_ULL(db_vector) for the corresponding doorbell bit. Use
> ntb_epf_db_vector_count() for bounds checks in ntb_epf_db_vector_mask(), so
> the same lower-bound guard is applied before building the bitmask.
> 
> Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>

Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>


> ---
> Changes since v3:
>   - Reuse ntb_epf_db_vector_count() from ntb_epf_db_vector_mask() for bounds.
>   - Return 0 when db_count is below NTB_EPF_MIN_DB_COUNT.
>   - Drop Reviewed-by tags due to the changes.
> 
>  drivers/ntb/hw/epf/ntb_hw_epf.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/drivers/ntb/hw/epf/ntb_hw_epf.c b/drivers/ntb/hw/epf/ntb_hw_epf.c
> index 10618e462229..af5755472842 100644
> --- a/drivers/ntb/hw/epf/ntb_hw_epf.c
> +++ b/drivers/ntb/hw/epf/ntb_hw_epf.c
> @@ -434,6 +434,36 @@ static u64 ntb_epf_db_valid_mask(struct ntb_dev *ntb)
>  	return ntb_ndev(ntb)->db_valid_mask;
>  }
>  
> +static int ntb_epf_db_vector_count(struct ntb_dev *ntb)
> +{
> +	struct ntb_epf_dev *ndev = ntb_ndev(ntb);
> +	unsigned int db_count = ndev->db_count;
> +
> +	/*
> +	 * db_count includes an extra skipped slot due to the legacy
> +	 * doorbell layout. Expose only the real doorbell vectors.
> +	 */
> +	if (db_count < NTB_EPF_MIN_DB_COUNT)
> +		return 0;
> +
> +	return db_count - 1;
> +}
> +
> +static u64 ntb_epf_db_vector_mask(struct ntb_dev *ntb, int db_vector)
> +{
> +	int nr_vec;
> +
> +	/*
> +	 * db_count includes one skipped slot in the legacy layout. Valid
> +	 * doorbell vectors are therefore [0 .. (db_count - 2)].
> +	 */
> +	nr_vec = ntb_epf_db_vector_count(ntb);
> +	if (db_vector < 0 || db_vector >= nr_vec)
> +		return 0;
> +
> +	return BIT_ULL(db_vector);
> +}
> +
>  static int ntb_epf_db_set_mask(struct ntb_dev *ntb, u64 db_bits)
>  {
>  	return 0;
> @@ -568,6 +598,8 @@ static const struct ntb_dev_ops ntb_epf_ops = {
>  	.spad_count		= ntb_epf_spad_count,
>  	.peer_mw_count		= ntb_epf_peer_mw_count,
>  	.db_valid_mask		= ntb_epf_db_valid_mask,
> +	.db_vector_count	= ntb_epf_db_vector_count,
> +	.db_vector_mask		= ntb_epf_db_vector_mask,
>  	.db_set_mask		= ntb_epf_db_set_mask,
>  	.mw_set_trans		= ntb_epf_mw_set_trans,
>  	.mw_clear_trans		= ntb_epf_mw_clear_trans,