iwlwifi: error checking for setting tx_power in sysfs

Perform error checking and report failure when setting tx power from
sysfs.
If fail to set the tx power, do not update the local copy, so user will
not see the incorrect tx power in sysfs
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn.c

@@ -2477,10 +2477,15 @@ static ssize_t store_tx_power(struct device *d,
 	ret = strict_strtoul(buf, 10, &val);
 	if (ret)
 		IWL_INFO(priv, "%s is not in decimal form.\n", buf);
+	else {
+		ret = iwl_set_tx_power(priv, val, false);
+		if (ret)
+			IWL_ERR(priv, "failed setting tx power (0x%d).\n",
+				ret);
 		else
-		iwl_set_tx_power(priv, val, false);
-
-	return count;
+			ret = count;
+	}
+	return ret;
 }
 
 static DEVICE_ATTR(tx_power, S_IWUSR | S_IRUGO, show_tx_power, store_tx_power);

drivers/net/wireless/iwlwifi/iwl-core.c

@@ -1701,6 +1701,8 @@ EXPORT_SYMBOL(iwl_init_drv);
 int iwl_set_tx_power(struct iwl_priv *priv, s8 tx_power, bool force)
 {
 	int ret = 0;
+	s8 prev_tx_power = priv->tx_power_user_lmt;
+
 	if (tx_power < IWL_TX_POWER_TARGET_POWER_MIN) {
 		IWL_WARN(priv, "Requested user TXPOWER %d below lower limit %d.\n",
 			 tx_power,
@@ -1718,15 +1720,27 @@ int iwl_set_tx_power(struct iwl_priv *priv, s8 tx_power, bool force)
 	if (priv->tx_power_user_lmt != tx_power)
 		force = true;
 
-	priv->tx_power_user_lmt = tx_power;
-
 	/* if nic is not up don't send command */
-	if (!iwl_is_ready_rf(priv))
-		return ret;
-
+	if (iwl_is_ready_rf(priv)) {
+		priv->tx_power_user_lmt = tx_power;
 		if (force && priv->cfg->ops->lib->send_tx_power)
 			ret = priv->cfg->ops->lib->send_tx_power(priv);
+		else if (!priv->cfg->ops->lib->send_tx_power)
+			ret = -EOPNOTSUPP;
+		/*
+		 * if fail to set tx_power, restore the orig. tx power
+		 */
+		if (ret)
+			priv->tx_power_user_lmt = prev_tx_power;
+	}
 
+	/*
+	 * Even this is an async host command, the command
+	 * will always report success from uCode
+	 * So once driver can placing the command into the queue
+	 * successfully, driver can use priv->tx_power_user_lmt
+	 * to reflect the current tx power
+	 */
 	return ret;
 }
 EXPORT_SYMBOL(iwl_set_tx_power);