p54: disable channels with incomplete calibration data sets

James Grossmann [1] reported that p54 spews out confusing
messages instead of preventing the mayhem from happening.

the reason is that "p54: generate channel list dynamically"
is not perfect. It didn't discard incomplete channel data
sets and therefore p54 advertised to support them as well.

[1]: http://marc.info/?l=linux-wireless&m=125699830215890

Cc: Larry Finger <Larry.Finger@lwfinger.net>
Reported-by: James Grossmann <cctsurf@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/p54/eeprom.c

@@ -126,7 +126,7 @@ static int p54_generate_band(struct ieee80211_hw *dev,
 	int ret = -ENOMEM;
 
 	if ((!list->entries) || (!list->band_channel_num[band]))
-		return 0;
+		return -EINVAL;
 
 	tmp = kzalloc(sizeof(*tmp), GFP_KERNEL);
 	if (!tmp)
@@ -158,6 +158,7 @@ static int p54_generate_band(struct ieee80211_hw *dev,
 			       (list->channels[i].data & CHAN_HAS_CURVE ? "" :
 				" [curve data]"),
 			       list->channels[i].index, list->channels[i].freq);
+			continue;
 		}
 
 		tmp->channels[j].band = list->channels[i].band;
@@ -165,7 +166,16 @@ static int p54_generate_band(struct ieee80211_hw *dev,
 		j++;
 	}
 
-	tmp->n_channels = list->band_channel_num[band];
+	if (j == 0) {
+		printk(KERN_ERR "%s: Disabling totally damaged %s band.\n",
+		       wiphy_name(dev->wiphy), (band == IEEE80211_BAND_2GHZ) ?
+		       "2 GHz" : "5 GHz");
+
+		ret = -ENODATA;
+		goto err_out;
+	}
+
+	tmp->n_channels = j;
 	old = priv->band_table[band];
 	priv->band_table[band] = tmp;
 	if (old) {
@@ -228,13 +238,13 @@ static int p54_generate_channel_lists(struct ieee80211_hw *dev)
 	struct p54_common *priv = dev->priv;
 	struct p54_channel_list *list;
 	unsigned int i, j, max_channel_num;
-	int ret = -ENOMEM;
+	int ret = 0;
 	u16 freq;
 
 	if ((priv->iq_autocal_len != priv->curve_data->entries) ||
 	    (priv->iq_autocal_len != priv->output_limit->entries))
-		printk(KERN_ERR "%s: EEPROM is damaged... you may not be able"
-				"to use all channels with this device.\n",
+		printk(KERN_ERR "%s: Unsupported or damaged EEPROM detected. "
+				"You may not be able to use all channels.\n",
 				wiphy_name(dev->wiphy));
 
 	max_channel_num = max_t(unsigned int, priv->output_limit->entries,
@@ -243,8 +253,10 @@ static int p54_generate_channel_lists(struct ieee80211_hw *dev)
 				priv->curve_data->entries);
 
 	list = kzalloc(sizeof(*list), GFP_KERNEL);
-	if (!list)
+	if (!list) {
+		ret = -ENOMEM;
 		goto free;
+	}
 
 	list->max_entries = max_channel_num;
 	list->channels = kzalloc(sizeof(struct p54_channel_entry) *
@@ -282,14 +294,9 @@ static int p54_generate_channel_lists(struct ieee80211_hw *dev)
 	     p54_compare_channels, NULL);
 
 	for (i = 0, j = 0; i < IEEE80211_NUM_BANDS; i++) {
-		if (list->band_channel_num[i]) {
-			ret = p54_generate_band(dev, list, i);
-			if (ret)
-				goto free;
-
+		if (p54_generate_band(dev, list, i) == 0)
 			j++;
 	}
-	}
 	if (j == 0) {
 		/* no useable band available. */
 		ret = -EINVAL;