diff options
| -rw-r--r-- | drivers/net/wireless/iwlwifi/pcie/tx.c | 36 |
1 files changed, 24 insertions, 12 deletions
diff --git a/drivers/net/wireless/iwlwifi/pcie/tx.c b/drivers/net/wireless/iwlwifi/pcie/tx.c index 011167c22da8..12c9c0030da6 100644 --- a/drivers/net/wireless/iwlwifi/pcie/tx.c +++ b/drivers/net/wireless/iwlwifi/pcie/tx.c @@ -65,18 +65,30 @@ ***************************************************/ static int iwl_queue_space(const struct iwl_queue *q) { - int s = q->read_ptr - q->write_ptr; - - if (q->read_ptr > q->write_ptr) - s -= q->n_bd; - - if (s <= 0) - s += q->n_window; - /* keep some reserve to not confuse empty and full situations */ - s -= 2; - if (s < 0) - s = 0; - return s; + unsigned int max; + unsigned int used; + + /* + * To avoid ambiguity between empty and completely full queues, there + * should always be less than q->n_bd elements in the queue. + * If q->n_window is smaller than q->n_bd, there is no need to reserve + * any queue entries for this purpose. + */ + if (q->n_window < q->n_bd) + max = q->n_window; + else + max = q->n_bd - 1; + + /* + * q->n_bd is a power of 2, so the following is equivalent to modulo by + * q->n_bd and is well defined for negative dividends. + */ + used = (q->write_ptr - q->read_ptr) & (q->n_bd - 1); + + if (WARN_ON(used > max)) + return 0; + + return max - used; } /* |