From: Ido Yariv <ido@xxxxxxxxxx>
Simplify iwl_rxq_space to improve readability and reduce
the ambiguity spares to a single element.
Signed-off-by: Ido Yariv <ido@xxxxxxxxxx>
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
---
drivers/net/wireless/iwlwifi/pcie/rx.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/drivers/net/wireless/iwlwifi/pcie/rx.c b/drivers/net/wireless/iwlwifi/pcie/rx.c
index 5fdb4ee..8c9641b 100644
--- a/drivers/net/wireless/iwlwifi/pcie/rx.c
+++ b/drivers/net/wireless/iwlwifi/pcie/rx.c
@@ -112,15 +112,16 @@
*/
static int iwl_rxq_space(const struct iwl_rxq *rxq)
{
- int s = rxq->read - rxq->write;
-
- if (s <= 0)
- s += RX_QUEUE_SIZE;
- /* keep some buffer to not confuse full and empty queue */
- s -= 2;
- if (s < 0)
- s = 0;
- return s;
+ /* Make sure RX_QUEUE_SIZE is a power of 2 */
+ BUILD_BUG_ON(RX_QUEUE_SIZE & (RX_QUEUE_SIZE - 1));
+
+ /*
+ * There can be up to (RX_QUEUE_SIZE - 1) free slots, to avoid ambiguity
+ * between empty and completely full queues.
+ * The following is equivalent to modulo by RX_QUEUE_SIZE and is well
+ * defined for negative dividends.
+ */
+ return (rxq->read - rxq->write - 1) & (RX_QUEUE_SIZE - 1);
}
/*
--
1.8.4.rc2
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