iwlwifi: refactor packet reception code

This patch fixes a number of issues in iwl_rx_reply_rx and
iwl_pass_packet_to_mac80211.  These issues stem from the complexities of
managing two different types of packet commands for different hardware.

- Unify code handling rx_phy_res in SKB or cached to eliminate redundancy and
remove potential NULL pointer accesses
- Replace magic number with proper constant
- Optimize functions by moving early exit conditions before computation
- Comment code and improve some variable names
- Remove redundant computation in iwl_pass_packet_to_mac80211 by passing in the
correct, already-computed arguments.

Signed-off-by: Daniel C Halperin <daniel.c.halperin@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 78 insertions, 127 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-commands.h b/drivers/net/wireless/iwlwifi/iwl-commands.h
index 68d7719071f7..9398ad7e42b1 100644
--- a/drivers/net/wireless/iwlwifi/iwl-commands.h
+++ b/drivers/net/wireless/iwlwifi/iwl-commands.h
@@ -1156,6 +1156,7 @@ struct iwl_wep_cmd {
 #define RX_RES_PHY_FLAGS_SHORT_PREAMBLE_MSK     cpu_to_le16(1 << 2)
 #define RX_RES_PHY_FLAGS_NARROW_BAND_MSK        cpu_to_le16(1 << 3)
 #define RX_RES_PHY_FLAGS_ANTENNA_MSK            cpu_to_le16(0xf0)
+#define RX_RES_PHY_FLAGS_ANTENNA_POS            4
 
 #define RX_RES_STATUS_SEC_TYPE_MSK      (0x7 << 8)
 #define RX_RES_STATUS_SEC_TYPE_NONE     (0x0 << 8)
diff --git a/drivers/net/wireless/iwlwifi/iwl-rx.c b/drivers/net/wireless/iwlwifi/iwl-rx.c
index 43b2fce4cbf0..092d3276175a 100644
--- a/drivers/net/wireless/iwlwifi/iwl-rx.c
+++ b/drivers/net/wireless/iwlwifi/iwl-rx.c
@@ -853,61 +853,12 @@ static u32 iwl_translate_rx_status(struct iwl_priv *priv, u32 decrypt_in)
 }
 
 static void iwl_pass_packet_to_mac80211(struct iwl_priv *priv,
-                                       int include_phy,
-                                       struct iwl_rx_mem_buffer *rxb,
-                                       struct ieee80211_rx_status *stats)
+                                        struct ieee80211_hdr *hdr,
+                                        u16 len,
+                                        u32 ampdu_status,
+                                        struct iwl_rx_mem_buffer *rxb,
+                                        struct ieee80211_rx_status *stats)
 {
-        struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;
-        struct iwl_rx_phy_res *rx_start = (include_phy) ?
-            (struct iwl_rx_phy_res *)&(pkt->u.raw[0]) : NULL;
-        struct ieee80211_hdr *hdr;
-        u16 len;
-        __le32 *rx_end;
-        unsigned int skblen;
-        u32 ampdu_status;
-        u32 ampdu_status_legacy;
-
-        if (!include_phy && priv->last_phy_res[0])
-                rx_start = (struct iwl_rx_phy_res *)&priv->last_phy_res[1];
-
-        if (!rx_start) {
-                IWL_ERR(priv, "MPDU frame without a PHY data\n");
-                return;
-        }
-        if (include_phy) {
-                hdr = (struct ieee80211_hdr *)((u8 *) &rx_start[1] +
-                                               rx_start->cfg_phy_cnt);
-
-                len = le16_to_cpu(rx_start->byte_count);
-
-                rx_end = (__le32 *)((u8 *) &pkt->u.raw[0] +
-                                  sizeof(struct iwl_rx_phy_res) +
-                                  rx_start->cfg_phy_cnt + len);
-
-        } else {
-                struct iwl4965_rx_mpdu_res_start *amsdu =
-                    (struct iwl4965_rx_mpdu_res_start *)pkt->u.raw;
-
-                hdr = (struct ieee80211_hdr *)(pkt->u.raw +
-                               sizeof(struct iwl4965_rx_mpdu_res_start));
-                len =  le16_to_cpu(amsdu->byte_count);
-                rx_start->byte_count = amsdu->byte_count;
-                rx_end = (__le32 *) (((u8 *) hdr) + len);
-        }
-
-        ampdu_status = le32_to_cpu(*rx_end);
-        skblen = ((u8 *) rx_end - (u8 *) &pkt->u.raw[0]) + sizeof(u32);
-
-        if (!include_phy) {
-                /* New status scheme, need to translate */
-                ampdu_status_legacy = ampdu_status;
-                ampdu_status = iwl_translate_rx_status(priv, ampdu_status);
-        }
-
-        /* start from MAC */
-        skb_reserve(rxb->skb, (void *)hdr - (void *)pkt);
-        skb_put(rxb->skb, len); /* end where data ends */
-
         /* We only process data packets if the interface is open */
         if (unlikely(!priv->is_open)) {
                 IWL_DEBUG_DROP_LIMIT(priv,
@@ -915,13 +866,15 @@ static void iwl_pass_packet_to_mac80211(struct iwl_priv *priv,
                 return;
         }
 
-        hdr = (struct ieee80211_hdr *)rxb->skb->data;
-
-        /*  in case of HW accelerated crypto and bad decryption, drop */
+        /* In case of HW accelerated crypto and bad decryption, drop */
         if (!priv->cfg->mod_params->sw_crypto &&
             iwl_set_decrypted_flag(priv, hdr, ampdu_status, stats))
                 return;
 
+        /* Resize SKB from mac header to end of packet */
+        skb_reserve(rxb->skb, (void *)hdr - (void *)rxb->skb->data);
+        skb_put(rxb->skb, len);
+
         iwl_update_stats(priv, false, hdr->frame_control, len);
         memcpy(IEEE80211_SKB_RXCB(rxb->skb), stats, sizeof(*stats));
         ieee80211_rx_irqsafe(priv->hw, rxb->skb);
@@ -955,25 +908,66 @@ void iwl_rx_reply_rx(struct iwl_priv *priv,
         struct ieee80211_hdr *header;
         struct ieee80211_rx_status rx_status;
         struct iwl_rx_packet *pkt = (struct iwl_rx_packet *)rxb->skb->data;
-        /* Use phy data (Rx signal strength, etc.) contained within
-         *   this rx packet for legacy frames,
-         *   or phy data cached from REPLY_RX_PHY_CMD for HT frames. */
-        int include_phy = (pkt->hdr.cmd == REPLY_RX);
-        struct iwl_rx_phy_res *rx_start = (include_phy) ?
-                (struct iwl_rx_phy_res *)&(pkt->u.raw[0]) :
-                (struct iwl_rx_phy_res *)&priv->last_phy_res[1];
-        __le32 *rx_end;
-        unsigned int len = 0;
+        struct iwl_rx_phy_res *phy_res;
+        __le32 rx_pkt_status;
+        struct iwl4965_rx_mpdu_res_start *amsdu;
+        u32 len;
+        u32 ampdu_status;
         u16 fc;
-        u8 network_packet;
 
-        rx_status.mactime = le64_to_cpu(rx_start->timestamp);
+        /**
+         * REPLY_RX and REPLY_RX_MPDU_CMD are handled differently.
+         *      REPLY_RX: physical layer info is in this buffer
+         *      REPLY_RX_MPDU_CMD: physical layer info was sent in separate
+         *              command and cached in priv->last_phy_res
+         *
+         * Here we set up local variables depending on which command is
+         * received.
+         */
+        if (pkt->hdr.cmd == REPLY_RX) {
+                phy_res = (struct iwl_rx_phy_res *)pkt->u.raw;
+                header = (struct ieee80211_hdr *)(pkt->u.raw + sizeof(*phy_res)
+                                + phy_res->cfg_phy_cnt);
+
+                len = le16_to_cpu(phy_res->byte_count);
+                rx_pkt_status = *(__le32 *)(pkt->u.raw + sizeof(*phy_res) +
+                                phy_res->cfg_phy_cnt + len);
+                ampdu_status = le32_to_cpu(rx_pkt_status);
+        } else {
+                if (!priv->last_phy_res[0]) {
+                        IWL_ERR(priv, "MPDU frame without cached PHY data\n");
+                        return;
+                }
+                phy_res = (struct iwl_rx_phy_res *)&priv->last_phy_res[1];
+                amsdu = (struct iwl4965_rx_mpdu_res_start *)pkt->u.raw;
+                header = (struct ieee80211_hdr *)(pkt->u.raw + sizeof(*amsdu));
+                len = le16_to_cpu(amsdu->byte_count);
+                rx_pkt_status = *(__le32 *)(pkt->u.raw + sizeof(*amsdu) + len);
+                ampdu_status = iwl_translate_rx_status(priv,
+                                le32_to_cpu(rx_pkt_status));
+        }
+
+        if ((unlikely(phy_res->cfg_phy_cnt > 20))) {
+                IWL_DEBUG_DROP(priv, "dsp size out of range [0,20]: %d/n",
+                                phy_res->cfg_phy_cnt);
+                return;
+        }
+
+        if (!(rx_pkt_status & RX_RES_STATUS_NO_CRC32_ERROR) ||
+            !(rx_pkt_status & RX_RES_STATUS_NO_RXE_OVERFLOW)) {
+                IWL_DEBUG_RX(priv, "Bad CRC or FIFO: 0x%08X.\n",
+                                le32_to_cpu(rx_pkt_status));
+                return;
+        }
+
+        /* rx_status carries information about the packet to mac80211 */
+        rx_status.mactime = le64_to_cpu(phy_res->timestamp);
         rx_status.freq =
-                ieee80211_channel_to_frequency(le16_to_cpu(rx_start->channel));
-        rx_status.band = (rx_start->phy_flags & RX_RES_PHY_FLAGS_BAND_24_MSK) ?
+                ieee80211_channel_to_frequency(le16_to_cpu(phy_res->channel));
+        rx_status.band = (phy_res->phy_flags & RX_RES_PHY_FLAGS_BAND_24_MSK) ?
                                 IEEE80211_BAND_2GHZ : IEEE80211_BAND_5GHZ;
         rx_status.rate_idx =
-                iwl_hwrate_to_plcp_idx(le32_to_cpu(rx_start->rate_n_flags));
+                iwl_hwrate_to_plcp_idx(le32_to_cpu(phy_res->rate_n_flags));
         if (rx_status.band == IEEE80211_BAND_5GHZ)
                 rx_status.rate_idx -= IWL_FIRST_OFDM_RATE;
 
@@ -983,54 +977,10 @@ void iwl_rx_reply_rx(struct iwl_priv *priv,
          * this W/A doesn't propagate it to the mac80211 */
         /*rx_status.flag |= RX_FLAG_TSFT;*/
 
-        if ((unlikely(rx_start->cfg_phy_cnt > 20))) {
-                IWL_DEBUG_DROP(priv, "dsp size out of range [0,20]: %d/n",
-                                rx_start->cfg_phy_cnt);
-                return;
-        }
-
-        if (!include_phy) {
-                if (priv->last_phy_res[0])
-                        rx_start = (struct iwl_rx_phy_res *)
-                                &priv->last_phy_res[1];
-                else
-                        rx_start = NULL;
-        }
-
-        if (!rx_start) {
-                IWL_ERR(priv, "MPDU frame without a PHY data\n");
-                return;
-        }
-
-        if (include_phy) {
-                header = (struct ieee80211_hdr *)((u8 *) &rx_start[1]
-                                                  + rx_start->cfg_phy_cnt);
-
-                len = le16_to_cpu(rx_start->byte_count);
-                rx_end = (__le32 *)(pkt->u.raw + rx_start->cfg_phy_cnt +
-                                  sizeof(struct iwl_rx_phy_res) + len);
-        } else {
-                struct iwl4965_rx_mpdu_res_start *amsdu =
-                        (struct iwl4965_rx_mpdu_res_start *)pkt->u.raw;
-
-                header = (void *)(pkt->u.raw +
-                        sizeof(struct iwl4965_rx_mpdu_res_start));
-                len = le16_to_cpu(amsdu->byte_count);
-                rx_end = (__le32 *) (pkt->u.raw +
-                        sizeof(struct iwl4965_rx_mpdu_res_start) + len);
-        }
-
-        if (!(*rx_end & RX_RES_STATUS_NO_CRC32_ERROR) ||
-            !(*rx_end & RX_RES_STATUS_NO_RXE_OVERFLOW)) {
-                IWL_DEBUG_RX(priv, "Bad CRC or FIFO: 0x%08X.\n",
-                                le32_to_cpu(*rx_end));
-                return;
-        }
-
-        priv->ucode_beacon_time = le32_to_cpu(rx_start->beacon_time_stamp);
+        priv->ucode_beacon_time = le32_to_cpu(phy_res->beacon_time_stamp);
 
         /* Find max signal strength (dBm) among 3 antenna/receiver chains */
-        rx_status.signal = iwl_calc_rssi(priv, rx_start);
+        rx_status.signal = iwl_calc_rssi(priv, phy_res);
 
         /* Meaningful noise values are available only from beacon statistics,
          *   which are gathered only when associated, and indicate noise
@@ -1050,10 +1000,10 @@ void iwl_rx_reply_rx(struct iwl_priv *priv,
         if (!iwl_is_associated(priv))
                 priv->last_rx_noise = IWL_NOISE_MEAS_NOT_AVAILABLE;
 
-        /* Set "1" to report good data frames in groups of 100 */
 #ifdef CONFIG_IWLWIFI_DEBUG
+        /* Set "1" to report good data frames in groups of 100 */
         if (unlikely(iwl_get_debug_level(priv) & IWL_DL_RX))
-                iwl_dbg_report_frame(priv, rx_start, len, header, 1);
+                iwl_dbg_report_frame(priv, phy_res, len, header, 1);
 #endif
         iwl_dbg_log_rx_data_frame(priv, len, header);
         IWL_DEBUG_STATS_LIMIT(priv, "Rssi %d, noise %d, qual %d, TSF %llu\n",
@@ -1073,18 +1023,18 @@ void iwl_rx_reply_rx(struct iwl_priv *priv,
          * new 802.11n radiotap field "RX chains" that is defined
          * as a bitmask.
          */
-        rx_status.antenna = le16_to_cpu(rx_start->phy_flags &
-                                        RX_RES_PHY_FLAGS_ANTENNA_MSK) >> 4;
+        rx_status.antenna =
+                le16_to_cpu(phy_res->phy_flags & RX_RES_PHY_FLAGS_ANTENNA_MSK)
+                >> RX_RES_PHY_FLAGS_ANTENNA_POS;
 
         /* set the preamble flag if appropriate */
-        if (rx_start->phy_flags & RX_RES_PHY_FLAGS_SHORT_PREAMBLE_MSK)
+        if (phy_res->phy_flags & RX_RES_PHY_FLAGS_SHORT_PREAMBLE_MSK)
                 rx_status.flag |= RX_FLAG_SHORTPRE;
 
-        network_packet = iwl_is_network_packet(priv, header);
-        if (network_packet) {
+        if (iwl_is_network_packet(priv, header)) {
                 priv->last_rx_rssi = rx_status.signal;
                 priv->last_beacon_time =  priv->ucode_beacon_time;
-                priv->last_tsf = le64_to_cpu(rx_start->timestamp);
+                priv->last_tsf = le64_to_cpu(phy_res->timestamp);
         }
 
         fc = le16_to_cpu(header->frame_control);
@@ -1096,8 +1046,8 @@ void iwl_rx_reply_rx(struct iwl_priv *priv,
                                                 header->addr2);
                 /* fall through */
         default:
-                        iwl_pass_packet_to_mac80211(priv, include_phy, rxb,
-                                   &rx_status);
+                iwl_pass_packet_to_mac80211(priv, header, len, ampdu_status,
+                                rxb, &rx_status);
                 break;
 
         }