Re: [PATCH 10/10] NTB: epf: Implement db_vector_count/mask for doorbells

On Tue, Feb 24, 2026 at 10:34:59PM +0900, 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.
>
> Signed-off-by: Koichiro Den <[email protected]>
> ---
>  drivers/ntb/hw/epf/ntb_hw_epf.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
>
> diff --git a/drivers/ntb/hw/epf/ntb_hw_epf.c b/drivers/ntb/hw/epf/ntb_hw_epf.c
> index 0018adc35f16..7c76039a79d2 100644
> --- a/drivers/ntb/hw/epf/ntb_hw_epf.c
> +++ b/drivers/ntb/hw/epf/ntb_hw_epf.c
> @@ -414,6 +414,34 @@ 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);
> +
> +	/*
> +	 * ndev->db_count includes an extra skipped slot due to the legacy
> +	 * doorbell layout. Expose only the real doorbell vectors.
> +	 */
> +	if (ndev->db_count < 1)
> +		return 0;
> +
> +	return ntb_ndev(ntb)->db_count - 1;

return max(ntb_ndev(ntb)->db_count - 1, 0);

Anyway: Reviewed-by: Frank Li <[email protected]>
> +}
> +
> +static u64 ntb_epf_db_vector_mask(struct ntb_dev *ntb, int db_vector)
> +{
> +	struct ntb_epf_dev *ndev = ntb_ndev(ntb);
> +
> +	/*
> +	 * ndev->db_count includes one skipped slot in the legacy layout. Valid
> +	 * doorbell vectors are therefore [0 .. (db_count - 2)].
> +	 */
> +	if (db_vector < 0 || db_vector >= ndev->db_count - 1)
> +		return 0;
> +
> +	return BIT_ULL(db_vector);
> +}
> +
>  static int ntb_epf_db_set_mask(struct ntb_dev *ntb, u64 db_bits)
>  {
>  	return 0;
> @@ -548,6 +576,8 @@ 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,
> --
> 2.51.0
>