xran: fix FDD operations and avoid skipping DL/UL slots.

Previously, is_tdd_ul_symbol() and is_tdd_dl_symbol() returned true
unconditionally in FDD. This is correct for UL/DL presence (in FDD,
every symbol carries both UL and DL), but it breaks logic that relies
on the TDD property that a UL symbol is not a DL symbol (and vice
versa), e.g. the computation of the last DL symbol in mixed slots. In
FDD, this assumption does not hold, leading to incorrect behavior.

Remove the FDD shortcut from the TDD symbol helpers so they strictly
answer the TDD question, and make the FDD case explicit at each
function call (nFrameDuplexType != XRAN_FDD && ...). This harmonizes
the TDD and FDD paths: in FDD, no slot/symbol is skipped on RX or TX,
and guard-slot handling only applies to TDD.
Signed-off-by: Karim Boutiba <karim.boutiba@openairinterface.org>

radio/fhi_72/oaioran.c

@@ -518,9 +518,6 @@ int xran_fh_rx_prach_read_slot(PHY_VARS_gNB *gNB, ru_info_t *ru, int *frame, int
  * @param sym_idx the current symbol index */
 static bool is_tdd_ul_symbol(const struct xran_frame_config *frame_conf, int slot, int sym_idx)
 {
-  /* in FDD, every symbol is also UL */
-  if (frame_conf->nFrameDuplexType == XRAN_FDD)
-    return true;
   int tdd_period = frame_conf->nTddPeriod;
   int slot_in_period = slot % tdd_period;
   /* check if symbol is UL */
@@ -534,9 +531,6 @@ static bool is_tdd_ul_symbol(const struct xran_frame_config *frame_conf, int slo
  * @param sym_idx the current symbol index */
 static bool is_tdd_dl_symbol(const struct xran_frame_config *frame_conf, int slot, int sym_idx)
 {
-  /* in FDD, every symbol is also UL */
-  if (frame_conf->nFrameDuplexType == XRAN_FDD)
-    return true;
   int tdd_period = frame_conf->nTddPeriod;
   int slot_in_period = slot % tdd_period;
   /* check if symbol is UL */
@@ -633,13 +627,13 @@ int xran_fh_rx_read_slot(ru_info_t *ru, int *frame, int *slot)
       start_ptr = rx_data + (slot_size * slot_offset_rxdata);
       const struct xran_frame_config *frame_conf = &get_xran_fh_config(ant_id / nb_rx_per_ru)->frame_conf;
       // skip processing this slot is TX (no RX in this slot)
-      if (!is_tdd_ul_guard_slot(frame_conf, *slot))
+      if (frame_conf->nFrameDuplexType != XRAN_FDD && !is_tdd_ul_guard_slot(frame_conf, *slot))
         continue;
       // This loop would better be more inner to avoid confusion and maybe also errors.
       for (int32_t sym_idx = 0; sym_idx < XRAN_NUM_OF_SYMBOL_PER_SLOT; sym_idx++) {
         /* the callback is for mixed and UL slots. In mixed, we have to
          * skip DL and guard symbols. */
-        if (!is_tdd_ul_symbol(frame_conf, *slot, sym_idx))
+        if (frame_conf->nFrameDuplexType != XRAN_FDD && !is_tdd_ul_symbol(frame_conf, *slot, sym_idx))
           continue;
 
         oran_buf_list_t *bufs = get_xran_buffers(ant_id / nb_rx_per_ru);
@@ -791,13 +785,13 @@ int xran_fh_tx_send_slot(ru_info_t *ru, int frame, int slot, uint64_t timestamp)
     for (uint8_t ant_id = 0; ant_id < ru->nb_rx; ant_id++) {
       const struct xran_frame_config *frame_conf = &get_xran_fh_config(ant_id / nb_rx_per_ru)->frame_conf;
       // skip processing this slot is TX (no RX in this slot)
-      if (!is_tdd_ul_guard_slot(frame_conf, slot)) {
+      if (frame_conf->nFrameDuplexType != XRAN_FDD && !is_tdd_ul_guard_slot(frame_conf, slot)) {
         continue;
       }
       // This loop would better be more inner to avoid confusion and maybe also errors.
       for (int32_t sym_idx = 0; sym_idx < XRAN_NUM_OF_SYMBOL_PER_SLOT; sym_idx++) {
         /* skip DL and guard symbols. */
-        if (!is_tdd_ul_symbol(frame_conf, slot, sym_idx)) {
+        if (frame_conf->nFrameDuplexType != XRAN_FDD && !is_tdd_ul_symbol(frame_conf, slot, sym_idx)) {
           continue;
         }
         oran_buf_list_t *bufs = get_xran_buffers(ant_id / nb_rx_per_ru);
@@ -832,7 +826,7 @@ int xran_fh_tx_send_slot(ru_info_t *ru, int frame, int slot, uint64_t timestamp)
       oran_buf_list_t *bufs = get_xran_buffers(ant_id / nb_tx_per_ru);
       const struct xran_frame_config *frame_conf = &get_xran_fh_config(ant_id / nb_tx_per_ru)->frame_conf;
       // skip processing this slot is TX (no TX in this slot)
-      if (!is_tdd_dl_guard_slot(frame_conf, slot)) {
+      if (frame_conf->nFrameDuplexType != XRAN_FDD && !is_tdd_dl_guard_slot(frame_conf, slot)) {
         continue;
       }
 
@@ -848,7 +842,7 @@ int xran_fh_tx_send_slot(ru_info_t *ru, int frame, int slot, uint64_t timestamp)
             break;
           }
         }
-        if (is_tdd_guard_slot(frame_conf, slot))
+        if (frame_conf->nFrameDuplexType != XRAN_FDD && is_tdd_guard_slot(frame_conf, slot))
           pRbMap->nPrbElm = dl_sym_end;
         else
           pRbMap->nPrbElm = XRAN_NUM_OF_SYMBOL_PER_SLOT;
@@ -857,7 +851,7 @@ int xran_fh_tx_send_slot(ru_info_t *ru, int frame, int slot, uint64_t timestamp)
       // This loop would better be more inner to avoid confusion and maybe also errors.
       for (int32_t sym_idx = 0; sym_idx < XRAN_NUM_OF_SYMBOL_PER_SLOT; sym_idx++) {
         /* skip UL and guard symbols. */
-        if (!is_tdd_dl_symbol(frame_conf, slot, sym_idx)) {
+        if (frame_conf->nFrameDuplexType != XRAN_FDD && !is_tdd_dl_symbol(frame_conf, slot, sym_idx)) {
           continue;
         }
         uint8_t *pData =