[PATCH net-next v2] r8169: expose software counters through netdev qstats

[Gustavo Arantes <dev.gustavoa@gmail.com>]

r8169 maintains synchronized per-CPU software counters for packet and
byte accounting and exposes them through ndo_get_stats64(), but
userspace using the structured netdev qstats API cannot retrieve them from
this driver.

Expose the same counters through netdev_stat_ops. r8169 has a single Rx
and Tx queue, so report the accumulated counters on queue 0. Use zero
base stats so device-scope qstats are derived from the queue counters
and match the packet and byte values reported through RTNL.

This does not add new accounting and does not touch the data path. It
only makes the existing counters available through the common qstats
interface, which lets generic userspace tooling query r8169 the same way
it queries other drivers with qstats support.

Signed-off-by: Gustavo Arantes <dev.gustavoa@gmail.com>
---
v2:
  - Submit again now that net-next has reopened.
  - Expand commit message to explain the qstats userspace benefit.

Tested on a Realtek RTL8111/8168/8211/8411 PCIe Gigabit Ethernet
controller using the r8169 driver.

v1: https://lore.kernel.org/netdev/20260418021232.5425-1-dev.gustavoa@gmail.com/

 drivers/net/ethernet/realtek/r8169_main.c | 70 +++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
index 791277e750ba..9d833b446383 100644
--- a/drivers/net/ethernet/realtek/r8169_main.c
+++ b/drivers/net/ethernet/realtek/r8169_main.c
@@ -5175,6 +5175,75 @@ rtl8169_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
 	pm_runtime_put_noidle(&pdev->dev);
 }

+static void rtl8169_fetch_sw_stats(struct net_device *dev,
+				   struct netdev_queue_stats_rx *rx,
+				   struct netdev_queue_stats_tx *tx)
+{
+	const struct pcpu_sw_netstats *stats;
+	unsigned int start;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		u64 rx_packets, rx_bytes, tx_packets, tx_bytes;
+
+		stats = per_cpu_ptr(dev->tstats, cpu);
+		do {
+			start = u64_stats_fetch_begin(&stats->syncp);
+			rx_packets = u64_stats_read(&stats->rx_packets);
+			rx_bytes = u64_stats_read(&stats->rx_bytes);
+			tx_packets = u64_stats_read(&stats->tx_packets);
+			tx_bytes = u64_stats_read(&stats->tx_bytes);
+		} while (u64_stats_fetch_retry(&stats->syncp, start));
+
+		rx->packets += rx_packets;
+		rx->bytes += rx_bytes;
+		tx->packets += tx_packets;
+		tx->bytes += tx_bytes;
+	}
+}
+
+static void rtl8169_get_queue_stats_rx(struct net_device *dev, int idx,
+				       struct netdev_queue_stats_rx *rx)
+{
+	struct netdev_queue_stats_tx tx = {};
+
+	if (idx)
+		return;
+
+	rx->packets = 0;
+	rx->bytes = 0;
+	rtl8169_fetch_sw_stats(dev, rx, &tx);
+}
+
+static void rtl8169_get_queue_stats_tx(struct net_device *dev, int idx,
+				       struct netdev_queue_stats_tx *tx)
+{
+	struct netdev_queue_stats_rx rx = {};
+
+	if (idx)
+		return;
+
+	tx->packets = 0;
+	tx->bytes = 0;
+	rtl8169_fetch_sw_stats(dev, &rx, tx);
+}
+
+static void rtl8169_get_base_stats(struct net_device *dev,
+				   struct netdev_queue_stats_rx *rx,
+				   struct netdev_queue_stats_tx *tx)
+{
+	rx->packets = 0;
+	rx->bytes = 0;
+	tx->packets = 0;
+	tx->bytes = 0;
+}
+
+static const struct netdev_stat_ops rtl8169_stat_ops = {
+	.get_queue_stats_rx	= rtl8169_get_queue_stats_rx,
+	.get_queue_stats_tx	= rtl8169_get_queue_stats_tx,
+	.get_base_stats		= rtl8169_get_base_stats,
+};
+
 static void rtl8169_net_suspend(struct rtl8169_private *tp)
 {
 	netif_device_detach(tp->dev);
@@ -5615,6 +5684,7 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)

 	SET_NETDEV_DEV(dev, &pdev->dev);
 	dev->netdev_ops = &rtl_netdev_ops;
+	dev->stat_ops = &rtl8169_stat_ops;
 	tp = netdev_priv(dev);
 	tp->dev = dev;
 	tp->pci_dev = pdev;
--
2.54.0