net: wifi_mgmt: linearise scan_params->chan arrays

Turn the nested arrays of `scan_params->chan` into a single array.
This adds the requirement to specify the band for each channel, but
eliminates the large amount of dead memory for unused bands. Overall,
this saves 50% of the RAM space for this variable.

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>

include/zephyr/net/wifi_mgmt.h

@@ -209,6 +209,16 @@ enum net_event_wifi_cmd {
 #define NET_EVENT_WIFI_DISCONNECT_COMPLETE			\
 	(_NET_WIFI_EVENT | NET_EVENT_WIFI_CMD_DISCONNECT_COMPLETE)
 
+/**
+ * @brief Wi-Fi structure to uniquely identify a band-channel pair
+ */
+struct wifi_band_channel {
+	/** Frequency band */
+	uint8_t band;
+	/** Channel */
+	uint8_t channel;
+};
+
 /**
  * @brief Wi-Fi scan parameters structure.
  * Used to specify parameters which can control how the Wi-Fi scan
@@ -248,9 +258,9 @@ struct wifi_scan_params {
 	 * band.
 	 * E.g. to scan channel 6 and 11 on the 2.4 GHz band, channel 36 on the 5 GHz band:
 	 * @code{.c}
-	 *     chan[WIFI_FREQ_BAND_2_4_GHZ][0] = 6;
+	 *     chan[0] = {WIFI_FREQ_BAND_2_4_GHZ, 6};
-	 *     chan[WIFI_FREQ_BAND_2_4_GHZ][1] = 11;
+	 *     chan[1] = {WIFI_FREQ_BAND_2_4_GHZ, 11};
-	 *     chan[WIFI_FREQ_BAND_5_GHZ][0] = 36;
+	 *     chan[2] = {WIFI_FREQ_BAND_5_GHZ, 36};
 	 * @endcode
 	 *
 	 *  This list specifies the channels to be __considered for scan__. The underlying
@@ -258,7 +268,7 @@ struct wifi_scan_params {
 	 *  not conforming to regulatory restrictions etc. The invoker of the API should
 	 *  ensure that the channels specified follow regulatory rules.
 	 */
-	uint8_t chan[WIFI_FREQ_BAND_MAX + 1][WIFI_MGMT_SCAN_CHAN_MAX_MANUAL];
+	struct wifi_band_channel band_chan[WIFI_MGMT_SCAN_CHAN_MAX_MANUAL];
 };
 
 /** Wi-Fi scan result, each result is provided to the net_mgmt_event_callback

include/zephyr/net/wifi_utils.h

@@ -95,12 +95,14 @@ int wifi_utils_parse_scan_ssids(char *scan_ssids_str,
  *
  * @param scan_chan_str List of channels expressed in the format described above.
  * @param chan Pointer to an array where the parsed channels are to be stored.
+ * @param max_channels Maximum number of channels to store
  *
  * @retval 0 on success.
  * @retval -errno value in case of failure.
  */
 int wifi_utils_parse_scan_chan(char *scan_chan_str,
-			       uint8_t chan[][WIFI_CHANNEL_MAX]);
+			       struct wifi_band_channel *chan,
+			       uint8_t max_channels);
 
 /**
  * @}

subsys/net/l2/wifi/Kconfig

@@ -48,11 +48,11 @@ config WIFI_MGMT_SCAN_SSID_FILT_MAX
 	  This can be set based on the underlying chipsets limitations.
 
 config WIFI_MGMT_SCAN_CHAN_MAX_MANUAL
-	int "Maximum number of channels that can be manually specified per-band"
+	int "Maximum number of channels that can be manually specified"
-	range 1 70
+	range 1 110
 	default 3
 	help
-	  There are currently 60 channels allocated in the largest band (6GHz).
+	  There are approximately 100 channels allocated across the three supported bands.
 	  The default of 3 allows the 3 most common channels (2.4GHz: 1, 6, 11) to be specified.
 
 config WIFI_NM

subsys/net/l2/wifi/wifi_shell.c

@@ -774,7 +774,9 @@ static int wifi_scan_args_to_params(const struct shell *sh,
 			opt_num++;
 			break;
 		case 'c':
-			if (wifi_utils_parse_scan_chan(optarg, params->chan)) {
+			if (wifi_utils_parse_scan_chan(optarg,
+						       params->band_chan,
+						       ARRAY_SIZE(params->band_chan))) {
 				shell_fprintf(sh,
 					      SHELL_ERROR,
 					      "Invalid band or channel value(s)\n");

subsys/net/l2/wifi/wifi_utils.c

@@ -105,7 +105,7 @@ static bool wifi_utils_validate_chan(uint8_t band,
 
 static int wifi_utils_get_all_chans_in_range(uint8_t chan_start,
 		uint8_t chan_end,
-		uint8_t chan[][WIFI_CHANNEL_MAX],
+		struct wifi_band_channel *band_chan,
 		uint8_t band_idx,
 		uint8_t *chan_idx)
 {
@@ -136,7 +136,9 @@ static int wifi_utils_get_all_chans_in_range(uint8_t chan_start,
 		idx = *chan_idx;
 
 		for (i = chan_start; i <= chan_end; i++) {
-			chan[band_idx][idx++] = i;
+			band_chan[idx].band = band_idx;
+			band_chan[idx].channel = i;
+			idx++;
 		}
 
 		*chan_idx = idx;
@@ -155,7 +157,9 @@ static int wifi_utils_get_all_chans_in_range(uint8_t chan_start,
 			}
 
 			if (start) {
-				chan[band_idx][idx++] = valid_5g_chans_20mhz[i];
+				band_chan[idx].band = band_idx;
+				band_chan[idx].channel = valid_5g_chans_20mhz[i];
+				idx++;
 			}
 
 			if (end) {
@@ -171,7 +175,9 @@ static int wifi_utils_get_all_chans_in_range(uint8_t chan_start,
 		i = chan_start;
 
 		while (i <= chan_end) {
-			chan[band_idx][idx++] = i;
+			band_chan[idx].band = band_idx;
+			band_chan[idx].channel = i;
+			idx++;
 
 			if (i == 1) {
 				i++;
@@ -310,7 +316,8 @@ int wifi_utils_parse_scan_ssids(char *scan_ssids_str,
 
 
 int wifi_utils_parse_scan_chan(char *scan_chan_str,
-			       uint8_t chan[][WIFI_CHANNEL_MAX])
+			       struct wifi_band_channel *band_chan,
+			       uint8_t max_channels)
 {
 	char band_str[WIFI_UTILS_MAX_BAND_STR_LEN] = {0};
 	char chan_str[WIFI_UTILS_MAX_CHAN_STR_LEN] = {0};
@@ -349,7 +356,6 @@ int wifi_utils_parse_scan_chan(char *scan_chan_str,
 		}
 
 		i++;
-		chan_idx = 0;
 		chan_str_start_idx = i;
 		valid_band = true;
 
@@ -383,9 +389,13 @@ int wifi_utils_parse_scan_chan(char *scan_chan_str,
 			memset(chan_str, 0, sizeof(chan_str));
 
 			if (chan_start) {
+				if ((chan_idx + (chan_val - chan_start)) >= max_channels) {
+					NET_ERR("Too many channels specified (%d)", max_channels);
+					return -EINVAL;
+				}
 				if (wifi_utils_get_all_chans_in_range(chan_start,
 								      chan_val,
-								      chan,
+								      band_chan,
 								      band,
 								      &chan_idx)) {
 					NET_ERR("Channel range invalid");
@@ -399,8 +409,14 @@ int wifi_utils_parse_scan_chan(char *scan_chan_str,
 					NET_ERR("Invalid channel %d", chan_val);
 					return -EINVAL;
 				}
+				if (chan_idx == max_channels) {
+					NET_ERR("Too many channels specified (%d)", max_channels);
+					return -EINVAL;
+				}
 
-				chan[band][chan_idx++] = chan_val;
+				band_chan[chan_idx].band = band;
+				band_chan[chan_idx].channel = chan_val;
+				chan_idx++;
 			}
 
 			valid_chan = true;