@@ -93,6 +93,12 @@ static int iwlagn_tx_status_reply_tx(struct iwl_priv *priv,
} else {
/* Two or more frames were attempted; expect block-ack */
u64 bitmap = 0;
+
+ /*
+ * Start is the lowest frame sent. It may not be the first
+ * frame in the batch; we figure this out dynamically during
+ * the following loop.
+ */
int start = agg->start_idx;
/* Construct bit-map of pending frames within Tx window */
@@ -131,25 +137,58 @@ static int iwlagn_tx_status_reply_tx(struct iwl_priv *priv,
IWL_DEBUG_TX_REPLY(priv, "AGG Frame i=%d idx %d seq=%d\n",
i, idx, SEQ_TO_SN(sc));
+ /*
+ * sh -> how many frames ahead of the starting frame is
+ * the current one?
+ *
+ * Note that all frames sent in the batch must be in a
+ * 64-frame window, so this number should be in [0,63].
+ * If outside of this window, then we've found a new
+ * "first" frame in the batch and need to change start.
+ */
sh = idx - start;
- if (sh > 64) {
- sh = (start - idx) + 0xff;
+
+ /*
+ * If >= 64, out of window. start must be at the front
+ * of the circular buffer, idx must be near the end of
+ * the buffer, and idx is the new "first" frame. Shift
+ * the indices around.
+ */
+ if (sh >= 64) {
+ /* Shift bitmap by start - idx, wrapped */
+ sh = 0x100 - idx + start;
bitmap = bitmap << sh;
+ /* Now idx is the new start so sh = 0 */
sh = 0;
start = idx;
- } else if (sh < -64)
- sh = 0xff - (start - idx);
- else if (sh < 0) {
+ /*
+ * If <= -64 then wraps the 256-pkt circular buffer
+ * (e.g., start = 255 and idx = 0, sh should be 1)
+ */
+ } else if (sh <= -64) {
+ sh = 0x100 - start + idx;
+ /*
+ * If < 0 but > -64, out of window. idx is before start
+ * but not wrapped. Shift the indices around.
+ */
+ } else if (sh < 0) {
+ /* Shift by how far start is ahead of idx */
sh = start - idx;
- start = idx;
bitmap = bitmap << sh;
+ /* Now idx is the new start so sh = 0 */
+ start = idx;
sh = 0;
}
+ /* Sequence number start + sh was sent in this batch */
bitmap |= 1ULL << sh;
IWL_DEBUG_TX_REPLY(priv, "start=%d bitmap=0x%llx\n",
start, (unsigned long long)bitmap);
}
+ /*
+ * Store the bitmap and possibly the new start, if we wrapped
+ * the buffer above
+ */
agg->bitmap = bitmap;
agg->start_idx = start;
IWL_DEBUG_TX_REPLY(priv, "Frames %d start_idx=%d bitmap=0x%llx\n",