[RFC PATCH 11/13] can: slcan: add ethtool support to reset adapter errors

From: Dario Binacchi
Date: Tue Jun 07 2022 - 05:49:59 EST

This patch adds a private flag to the slcan driver to switch the
"err-rst-on-open" setting on and off.

"err-rst-on-open" on - Reset error states on opening command

"err-rst-on-open" off - Don't reset error states on opening command
(default)

The setting can only be changed if the interface is down:

ip link set dev can0 down
ethtool --set-priv-flags can0 err-rst-on-open {off|on}
ip link set dev can0 up

Signed-off-by: Dario Binacchi <dario.binacchi@xxxxxxxxxxxxxxxxxxxx>
---

drivers/net/can/slcan/Makefile | 1 +
drivers/net/can/slcan/slcan-core.c | 36 +++++++++++++++
drivers/net/can/slcan/slcan-ethtool.c | 65 +++++++++++++++++++++++++++
drivers/net/can/slcan/slcan.h | 18 ++++++++
4 files changed, 120 insertions(+)
create mode 100644 drivers/net/can/slcan/slcan-ethtool.c
create mode 100644 drivers/net/can/slcan/slcan.h

diff --git a/drivers/net/can/slcan/Makefile b/drivers/net/can/slcan/Makefile
index 2e84f7bf7617..8a88e484ee21 100644
--- a/drivers/net/can/slcan/Makefile
+++ b/drivers/net/can/slcan/Makefile
@@ -4,3 +4,4 @@ obj-$(CONFIG_CAN_SLCAN) += slcan.o

slcan-objs :=
slcan-objs += slcan-core.o
+slcan-objs += slcan-ethtool.o
diff --git a/drivers/net/can/slcan/slcan-core.c b/drivers/net/can/slcan/slcan-core.c
index d63d270d21da..b813a59534a3 100644
--- a/drivers/net/can/slcan/slcan-core.c
+++ b/drivers/net/can/slcan/slcan-core.c
@@ -57,6 +57,8 @@
#include <linux/can/dev.h>
#include <linux/can/skb.h>

+#include "slcan.h"
+
MODULE_ALIAS_LDISC(N_SLCAN);
MODULE_DESCRIPTION("serial line CAN interface");
MODULE_LICENSE("GPL");
@@ -98,6 +100,8 @@ struct slcan {
#define SLF_INUSE 0 /* Channel in use */
#define SLF_ERROR 1 /* Parity, etc. error */
#define SLF_XCMD 2 /* Command transmission */
+ unsigned long cmd_flags; /* Command flags */
+#define CF_ERR_RST 0 /* Reset errors on open */
wait_queue_head_t xcmd_wait; /* Wait queue for commands */
/* transmission */
};
@@ -117,6 +121,28 @@ static const struct can_bittiming_const slcan_bittiming_const = {
.brp_inc = 1,
};

+bool slcan_err_rst_on_open(struct net_device *ndev)
+{
+ struct slcan *sl = netdev_priv(ndev);
+
+ return !!test_bit(CF_ERR_RST, &sl->cmd_flags);
+}
+
+int slcan_enable_err_rst_on_open(struct net_device *ndev, bool on)
+{
+ struct slcan *sl = netdev_priv(ndev);
+
+ if (netif_running(ndev))
+ return -EBUSY;
+
+ if (on)
+ set_bit(CF_ERR_RST, &sl->cmd_flags);
+ else
+ clear_bit(CF_ERR_RST, &sl->cmd_flags);
+
+ return 0;
+}
+
/************************************************************************
* SLCAN ENCAPSULATION FORMAT *
************************************************************************/
@@ -483,6 +509,15 @@ static int slc_open(struct net_device *dev)
if (sl->can.bittiming.bitrate == 0) {
sl->can.bittiming.bitrate = -1UL;
} else {
+ if (test_bit(CF_ERR_RST, &sl->cmd_flags)) {
+ err = slcan_transmit_cmd(sl, "F\r");
+ if (err) {
+ netdev_err(sl->dev,
+ "failed to send error command 'F\\r'\n");
+ return err;
+ }
+ }
+
err = slcan_transmit_cmd(sl, "O\r");
if (err) {
netdev_err(dev, "failed to send open command 'O\\r'\n");
@@ -645,6 +680,7 @@ static struct slcan *slc_alloc(void)

snprintf(dev->name, sizeof(dev->name), "slcan%d", i);
dev->netdev_ops = &slc_netdev_ops;
+ slcan_set_ethtool_ops(dev);
sl = netdev_priv(dev);

/* Initialize channel control data */
diff --git a/drivers/net/can/slcan/slcan-ethtool.c b/drivers/net/can/slcan/slcan-ethtool.c
new file mode 100644
index 000000000000..bf0afdc4e49d
--- /dev/null
+++ b/drivers/net/can/slcan/slcan-ethtool.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* Copyright (c) 2022 Amarula Solutions, Dario Binacchi <dario.binacchi@xxxxxxxxxxxxxxxxxxxx>
+ *
+ */
+
+#include <linux/can/dev.h>
+#include <linux/ethtool.h>
+#include <linux/kernel.h>
+#include <linux/netdevice.h>
+#include <linux/platform_device.h>
+
+#include "slcan.h"
+
+static const char slcan_priv_flags_strings[][ETH_GSTRING_LEN] = {
+#define SLCAN_PRIV_FLAGS_ERR_RST_ON_OPEN BIT(0)
+ "err-rst-on-open",
+};
+
+static void slcan_get_strings(struct net_device *ndev, u32 stringset, u8 *data)
+{
+ switch (stringset) {
+ case ETH_SS_PRIV_FLAGS:
+ memcpy(data, slcan_priv_flags_strings,
+ sizeof(slcan_priv_flags_strings));
+ }
+}
+
+static u32 slcan_get_priv_flags(struct net_device *ndev)
+{
+ u32 flags = 0;
+
+ if (slcan_err_rst_on_open(ndev))
+ flags |= SLCAN_PRIV_FLAGS_ERR_RST_ON_OPEN;
+
+ return flags;
+}
+
+static int slcan_set_priv_flags(struct net_device *ndev, u32 flags)
+{
+ bool err_rst_op_open = !!(flags & SLCAN_PRIV_FLAGS_ERR_RST_ON_OPEN);
+
+ return slcan_enable_err_rst_on_open(ndev, err_rst_op_open);
+}
+
+static int slcan_get_sset_count(struct net_device *netdev, int sset)
+{
+ switch (sset) {
+ case ETH_SS_PRIV_FLAGS:
+ return ARRAY_SIZE(slcan_priv_flags_strings);
+ default:
+ return -EOPNOTSUPP;
+ }
+}
+
+static const struct ethtool_ops slcan_ethtool_ops = {
+ .get_strings = slcan_get_strings,
+ .get_priv_flags = slcan_get_priv_flags,
+ .set_priv_flags = slcan_set_priv_flags,
+ .get_sset_count = slcan_get_sset_count,
+};
+
+void slcan_set_ethtool_ops(struct net_device *netdev)
+{
+ netdev->ethtool_ops = &slcan_ethtool_ops;
+}
diff --git a/drivers/net/can/slcan/slcan.h b/drivers/net/can/slcan/slcan.h
new file mode 100644
index 000000000000..d463c8d99e22
--- /dev/null
+++ b/drivers/net/can/slcan/slcan.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0
+ * slcan.h - serial line CAN interface driver
+ *
+ * Copyright (C) Laurence Culhane <loz@xxxxxxxxxxxxxxxxxx>
+ * Copyright (C) Fred N. van Kempen <waltje@xxxxxxxxxxxxxxxxxxx>
+ * Copyright (C) Oliver Hartkopp <socketcan@xxxxxxxxxxxx>
+ * Copyright (C) 2022 Amarula Solutions, Dario Binacchi <dario.binacchi@xxxxxxxxxxxxxxxxxxxx>
+ *
+ */
+
+#ifndef _SLCAN_H
+#define _SLCAN_H
+
+bool slcan_err_rst_on_open(struct net_device *ndev);
+int slcan_enable_err_rst_on_open(struct net_device *ndev, bool on);
+void slcan_set_ethtool_ops(struct net_device *ndev);
+
+#endif /* _SLCAN_H */
--
2.32.0