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

[Koichiro Den]

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>
---
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,
-- 
2.51.0