sfxge(4): add firmware subvariant aware driver option

[arybchik]

Summary

FW subvariants allow to tweak NIC global features. For example,
if no drivers require checksumming on transmit, it may be disabled
in FW to increase packet rate.

Sponsored by: Solarflare Communications, Inc.

Test Plan

amd64 tinderbox kernel builds tested
driver loaded/unloaded, interfaces up/down, traffic works fine

head/sys/dev/sfxge/common/efsys.h

if (th->th_seq == tp->rcv_nxt &&
                          * theoretically invalid by now.  Fortunately
                          * m_adj() doesn't actually frees any mbufs
                          * when trimming from the head.
                          */
                         tcp_seq temp = save_start;
                         thflags = tcp_reass(tp, th, &temp, &tlen, m);
                         tp->t_flags |= TF_ACKNOW;
                 }
-                if (tp->t_flags & TF_SACK_PERMIT) {
-                        if (((tlen == 0) && (save_tlen > 0) &&
-                            (SEQ_LT(save_start, save_rnxt)))) {
+                if ((tp->t_flags & TF_SACK_PERMIT) && (save_tlen > 0)) {
+                        if ((tlen == 0) && (SEQ_LT(save_start, save_rnxt))) {
                                 /*
                                  * DSACK actually handled in the fastpath
                                  * above.
                                  */
                                 tcp_update_sack_list(tp, save_start,
                                     save_start + save_tlen);
                         } else if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) {
-                                /*
-                                 * Cleaning sackblks by using zero length
-                                 * update.
-                                 */
                                 if ((tp->rcv_numsacks >= 1) &&
                                     (tp->sackblks[0].end == save_start)) {
-                                        /* partial overlap, recorded at todrop above */
-                                        tcp_update_sack_list(tp, tp->sackblks[0].start,
+                                        /*
+                                         * Partial overlap, recorded at todrop
+                                         * above.
+                                         */
+                                        tcp_update_sack_list(tp,
+                                            tp->sackblks[0].start,
                                             tp->sackblks[0].end);
                                 } else {
                                         tcp_update_dsack_list(tp, save_start,
                                             save_start + save_tlen);
                                 }
-                        } else if ((tlen > 0) && (tlen >= save_tlen)) {
+                        } else if (tlen >= save_tlen) {
                                 /* Update of sackblks. */
                                 tcp_update_dsack_list(tp, save_start,
                                     save_start + save_tlen);
                         } else if (tlen > 0) {
                                 tcp_update_dsack_list(tp, save_start,
                                     save_start + tlen);
                         }
                 }

head/sys/dev/sfxge/common/efx_check.h

if (th->th_seq == tp->rcv_nxt &&
                          * theoretically invalid by now.  Fortunately
                          * m_adj() doesn't actually frees any mbufs
                          * when trimming from the head.
                          */
                         tcp_seq temp = save_start;
                         thflags = tcp_reass(tp, th, &temp, &tlen, m);
                         tp->t_flags |= TF_ACKNOW;
                 }
-                if (tp->t_flags & TF_SACK_PERMIT) {
-                        if (((tlen == 0) && (save_tlen > 0) &&
-                            (SEQ_LT(save_start, save_rnxt)))) {
+                if ((tp->t_flags & TF_SACK_PERMIT) && (save_tlen > 0)) {
+                        if ((tlen == 0) && (SEQ_LT(save_start, save_rnxt))) {
                                 /*
                                  * DSACK actually handled in the fastpath
                                  * above.
                                  */
                                 tcp_update_sack_list(tp, save_start,
                                     save_start + save_tlen);
                         } else if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) {
-                                /*
-                                 * Cleaning sackblks by using zero length
-                                 * update.
-                                 */
                                 if ((tp->rcv_numsacks >= 1) &&
                                     (tp->sackblks[0].end == save_start)) {
-                                        /* partial overlap, recorded at todrop above */
-                                        tcp_update_sack_list(tp, tp->sackblks[0].start,
+                                        /*
+                                         * Partial overlap, recorded at todrop
+                                         * above.
+                                         */
+                                        tcp_update_sack_list(tp,
+                                            tp->sackblks[0].start,
                                             tp->sackblks[0].end);
                                 } else {
                                         tcp_update_dsack_list(tp, save_start,
                                             save_start + save_tlen);
                                 }
-                        } else if ((tlen > 0) && (tlen >= save_tlen)) {
+                        } else if (tlen >= save_tlen) {
                                 /* Update of sackblks. */
                                 tcp_update_dsack_list(tp, save_start,
                                     save_start + save_tlen);
                         } else if (tlen > 0) {
                                 tcp_update_dsack_list(tp, save_start,
                                     save_start + tlen);
                         }
                 }

head/sys/dev/sfxge/common/efx_mcdi.c

if (th->th_seq == tp->rcv_nxt &&
                          * theoretically invalid by now.  Fortunately
                          * m_adj() doesn't actually frees any mbufs
                          * when trimming from the head.
                          */
                         tcp_seq temp = save_start;
                         thflags = tcp_reass(tp, th, &temp, &tlen, m);
                         tp->t_flags |= TF_ACKNOW;
                 }
-                if (tp->t_flags & TF_SACK_PERMIT) {
-                        if (((tlen == 0) && (save_tlen > 0) &&
-                            (SEQ_LT(save_start, save_rnxt)))) {
+                if ((tp->t_flags & TF_SACK_PERMIT) && (save_tlen > 0)) {
+                        if ((tlen == 0) && (SEQ_LT(save_start, save_rnxt))) {
                                 /*
                                  * DSACK actually handled in the fastpath
                                  * above.
                                  */
                                 tcp_update_sack_list(tp, save_start,
                                     save_start + save_tlen);
                         } else if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) {
-                                /*
-                                 * Cleaning sackblks by using zero length
-                                 * update.
-                                 */
                                 if ((tp->rcv_numsacks >= 1) &&
                                     (tp->sackblks[0].end == save_start)) {
-                                        /* partial overlap, recorded at todrop above */
-                                        tcp_update_sack_list(tp, tp->sackblks[0].start,
+                                        /*
+                                         * Partial overlap, recorded at todrop
+                                         * above.
+                                         */
+                                        tcp_update_sack_list(tp,
+                                            tp->sackblks[0].start,
                                             tp->sackblks[0].end);
                                 } else {
                                         tcp_update_dsack_list(tp, save_start,
                                             save_start + save_tlen);
                                 }
-                        } else if ((tlen > 0) && (tlen >= save_tlen)) {
+                        } else if (tlen >= save_tlen) {
                                 /* Update of sackblks. */
                                 tcp_update_dsack_list(tp, save_start,
                                     save_start + save_tlen);
                         } else if (tlen > 0) {
                                 tcp_update_dsack_list(tp, save_start,
                                     save_start + tlen);
                         }
                 }