iwlwifi: fix iwl_legacy_rate_to_fw_idx

There are a couple of bugs in this function:

1. It is declared as a non-static function, even though
   it's only used in one file.
2. Its return value should be of type u32 but it returns
   (in some cases) -1.

Fix them by making this function static and returning an
error value of type unsigned.

In addition, we're assigning the return value of this function
as the legacy rate even if the function returned an error value.
Fix this by assigning the lowest rate in this case.

Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Reported-by: Ye Guojin <ye.guojin@zte.com.cn>
Reported-by: Zeal Robot <zealci@zte.com.cn>
Fixes: 9998f81 ("iwlwifi: mvm: convert old rate & flags to the new format.")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/iwlwifi.20220128142706.5612eeb9d6d0.I992e10d93fc22919b2bc42daad087ee1b5d6f014@changeid

drivers/net/wireless/intel/iwlwifi/fw/api/rs.h

@@ -752,7 +752,6 @@ struct iwl_lq_cmd {
 
 u8 iwl_fw_rate_idx_to_plcp(int idx);
 u32 iwl_new_rate_from_v1(u32 rate_v1);
-u32 iwl_legacy_rate_to_fw_idx(u32 rate_n_flags);
 const struct iwl_rate_mcs_info *iwl_rate_mcs(int idx);
 const char *iwl_rs_pretty_ant(u8 ant);
 const char *iwl_rs_pretty_bw(int bw);

drivers/net/wireless/intel/iwlwifi/fw/rs.c

@@ -91,6 +91,20 @@ const char *iwl_rs_pretty_bw(int bw)
 }
 IWL_EXPORT_SYMBOL(iwl_rs_pretty_bw);
 
+static u32 iwl_legacy_rate_to_fw_idx(u32 rate_n_flags)
+{
+	int rate = rate_n_flags & RATE_LEGACY_RATE_MSK_V1;
+	int idx;
+	bool ofdm = !(rate_n_flags & RATE_MCS_CCK_MSK_V1);
+	int offset = ofdm ? IWL_FIRST_OFDM_RATE : 0;
+	int last = ofdm ? IWL_RATE_COUNT_LEGACY : IWL_FIRST_OFDM_RATE;
+
+	for (idx = offset; idx < last; idx++)
+		if (iwl_fw_rate_idx_to_plcp(idx) == rate)
+			return idx - offset;
+	return IWL_RATE_INVALID;
+}
+
 u32 iwl_new_rate_from_v1(u32 rate_v1)
 {
 	u32 rate_v2 = 0;
@@ -144,7 +158,10 @@ u32 iwl_new_rate_from_v1(u32 rate_v1)
 	} else {
 		u32 legacy_rate = iwl_legacy_rate_to_fw_idx(rate_v1);
 
-		WARN_ON(legacy_rate < 0);
+		if (WARN_ON_ONCE(legacy_rate == IWL_RATE_INVALID))
+			legacy_rate = (rate_v1 & RATE_MCS_CCK_MSK_V1) ?
+				IWL_FIRST_CCK_RATE : IWL_FIRST_OFDM_RATE;
+
 		rate_v2 |= legacy_rate;
 		if (!(rate_v1 & RATE_MCS_CCK_MSK_V1))
 			rate_v2 |= RATE_MCS_LEGACY_OFDM_MSK;
@@ -172,20 +189,6 @@ u32 iwl_new_rate_from_v1(u32 rate_v1)
 }
 IWL_EXPORT_SYMBOL(iwl_new_rate_from_v1);
 
-u32 iwl_legacy_rate_to_fw_idx(u32 rate_n_flags)
-{
-	int rate = rate_n_flags & RATE_LEGACY_RATE_MSK_V1;
-	int idx;
-	bool ofdm = !(rate_n_flags & RATE_MCS_CCK_MSK_V1);
-	int offset = ofdm ? IWL_FIRST_OFDM_RATE : 0;
-	int last = ofdm ? IWL_RATE_COUNT_LEGACY : IWL_FIRST_OFDM_RATE;
-
-	for (idx = offset; idx < last; idx++)
-		if (iwl_fw_rate_idx_to_plcp(idx) == rate)
-			return idx - offset;
-	return -1;
-}
-
 int rs_pretty_print_rate(char *buf, int bufsz, const u32 rate)
 {
 	char *type;