leds: trigger: netdev: Add support for tx_err and rx_err notification with LEDs

This patch provides support for enabling blinking of LEDs when RX or TX
errors are detected.

Approach taken in this patch is similar to one for TX or RX data
transmission indication (i.e. TRIGGER_NETDEV_TX/RX attribute).

One can inspect transmission errors with:
ip -s link show eth0

Example LED configuration:
cd /sys/devices/platform/amba_pl@0/a001a000.leds/leds/
echo netdev > mode:blue/trigger && \
echo eth0 > mode:blue/device_name && \
echo 1 > mode:blue/tx_err

Signed-off-by: Lukasz Majewski <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

drivers/leds/trigger/ledtrig-netdev.c

···
  *         (has carrier) or not
  * tx -  LED blinks on transmitted data
  * rx -  LED blinks on receive data
+ * tx_err -  LED blinks on transmit error
+ * rx_err -  LED blinks on receive error
  *
  * Note: If the user selects a mode that is not supported by hw, default
  * behavior is to fall back to software control of the LED. However not every
···
 		 * checking stats
 		 */
 		if (test_bit(TRIGGER_NETDEV_TX, &trigger_data->mode) ||
-		    test_bit(TRIGGER_NETDEV_RX, &trigger_data->mode))
+		    test_bit(TRIGGER_NETDEV_RX, &trigger_data->mode) ||
+		    test_bit(TRIGGER_NETDEV_TX_ERR, &trigger_data->mode) ||
+		    test_bit(TRIGGER_NETDEV_RX_ERR, &trigger_data->mode))
 			schedule_delayed_work(&trigger_data->work, 0);
 	}
 }
···
 	case TRIGGER_NETDEV_FULL_DUPLEX:
 	case TRIGGER_NETDEV_TX:
 	case TRIGGER_NETDEV_RX:
+	case TRIGGER_NETDEV_TX_ERR:
+	case TRIGGER_NETDEV_RX_ERR:
 		bit = attr;
 		break;
 	default:
···
 	case TRIGGER_NETDEV_FULL_DUPLEX:
 	case TRIGGER_NETDEV_TX:
 	case TRIGGER_NETDEV_RX:
+	case TRIGGER_NETDEV_TX_ERR:
+	case TRIGGER_NETDEV_RX_ERR:
 		bit = attr;
 		break;
 	default:
···
 DEFINE_NETDEV_TRIGGER(full_duplex, TRIGGER_NETDEV_FULL_DUPLEX);
 DEFINE_NETDEV_TRIGGER(tx, TRIGGER_NETDEV_TX);
 DEFINE_NETDEV_TRIGGER(rx, TRIGGER_NETDEV_RX);
+DEFINE_NETDEV_TRIGGER(tx_err, TRIGGER_NETDEV_TX_ERR);
+DEFINE_NETDEV_TRIGGER(rx_err, TRIGGER_NETDEV_RX_ERR);
 
 static ssize_t interval_show(struct device *dev,
 			     struct device_attribute *attr, char *buf)
···
 	&dev_attr_half_duplex.attr,
 	&dev_attr_rx.attr,
 	&dev_attr_tx.attr,
+	&dev_attr_rx_err.attr,
+	&dev_attr_tx_err.attr,
 	&dev_attr_interval.attr,
 	&dev_attr_offloaded.attr,
 	NULL
···
 
 	/* If we are not looking for RX/TX then return  */
 	if (!test_bit(TRIGGER_NETDEV_TX, &trigger_data->mode) &&
-	    !test_bit(TRIGGER_NETDEV_RX, &trigger_data->mode))
+	    !test_bit(TRIGGER_NETDEV_RX, &trigger_data->mode) &&
+	    !test_bit(TRIGGER_NETDEV_TX_ERR, &trigger_data->mode) &&
+	    !test_bit(TRIGGER_NETDEV_RX_ERR, &trigger_data->mode))
 		return;
 
 	dev_stats = dev_get_stats(trigger_data->net_dev, &temp);
···
 	    (test_bit(TRIGGER_NETDEV_TX, &trigger_data->mode) ?
 		dev_stats->tx_packets : 0) +
 	    (test_bit(TRIGGER_NETDEV_RX, &trigger_data->mode) ?
-		dev_stats->rx_packets : 0);
+		dev_stats->rx_packets : 0) +
+	    (test_bit(TRIGGER_NETDEV_TX_ERR, &trigger_data->mode) ?
+		dev_stats->tx_errors : 0) +
+	    (test_bit(TRIGGER_NETDEV_RX_ERR, &trigger_data->mode) ?
+		dev_stats->rx_errors : 0);
 
 	if (trigger_data->last_activity != new_activity) {
 		led_stop_software_blink(trigger_data->led_cdev);

include/linux/leds.h

···
 	TRIGGER_NETDEV_FULL_DUPLEX,
 	TRIGGER_NETDEV_TX,
 	TRIGGER_NETDEV_RX,
+	TRIGGER_NETDEV_TX_ERR,
+	TRIGGER_NETDEV_RX_ERR,
 
 	/* Keep last */
 	__TRIGGER_NETDEV_MAX,