can: peak_usb: add ethtool interface to user-configurable CAN channel identifier

This patch introduces 3 new functions implementing support for ethtool
access to the CAN channel ID of all USB CAN network interfaces managed by
the driver. With this patch, it is possible to read/write the CAN
channel ID from/to the EEPROM via the ethtool interface.

The CAN channel ID is a user-configurable device identifier that can be
set individually for each CAN interface of a PEAK USB device. Depending on
the device, the identifier has a length of 8 or 32 bit. The identifier
is stored in the non-volatile memory of the device.

The identifier of a CAN interface can be read/written as an 8 or 32 bit
byte string in native (little-endian) byte order, where the length depends
on the device type.

Signed-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Signed-off-by: Lukas Magel <lukas.magel@posteo.net>
Link: https://lore.kernel.org/all/20230116200932.157769-6-lukas.magel@posteo.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/usb/peak_usb/pcan_usb.c

@@ -982,9 +982,18 @@ static int pcan_usb_set_phys_id(struct net_device *netdev,
 	return err;
 }
 
+/* This device only handles 8-bit CAN channel id. */
+static int pcan_usb_get_eeprom_len(struct net_device *netdev)
+{
+	return sizeof(u8);
+}
+
 static const struct ethtool_ops pcan_usb_ethtool_ops = {
 	.set_phys_id = pcan_usb_set_phys_id,
 	.get_ts_info = pcan_get_ts_info,
+	.get_eeprom_len	= pcan_usb_get_eeprom_len,
+	.get_eeprom = peak_usb_get_eeprom,
+	.set_eeprom = peak_usb_set_eeprom,
 };
 
 /*

drivers/net/can/usb/peak_usb/pcan_usb_core.c

@@ -808,6 +808,86 @@ static const struct net_device_ops peak_usb_netdev_ops = {
 	.ndo_change_mtu = can_change_mtu,
 };
 
+/* CAN-USB devices generally handle 32-bit CAN channel IDs.
+ * In case one doesn't, then it have to overload this function.
+ */
+int peak_usb_get_eeprom_len(struct net_device *netdev)
+{
+	return sizeof(u32);
+}
+
+/* Every CAN-USB device exports the dev_get_can_channel_id() operation. It is used
+ * here to fill the data buffer with the user defined CAN channel ID.
+ */
+int peak_usb_get_eeprom(struct net_device *netdev,
+			struct ethtool_eeprom *eeprom, u8 *data)
+{
+	struct peak_usb_device *dev = netdev_priv(netdev);
+	u32 ch_id;
+	__le32 ch_id_le;
+	int err;
+
+	err = dev->adapter->dev_get_can_channel_id(dev, &ch_id);
+	if (err)
+		return err;
+
+	/* ethtool operates on individual bytes. The byte order of the CAN
+	 * channel id in memory depends on the kernel architecture. We
+	 * convert the CAN channel id back to the native byte order of the PEAK
+	 * device itself to ensure that the order is consistent for all
+	 * host architectures.
+	 */
+	ch_id_le = cpu_to_le32(ch_id);
+	memcpy(data, (u8 *)&ch_id_le + eeprom->offset, eeprom->len);
+
+	/* update cached value */
+	dev->can_channel_id = ch_id;
+	return err;
+}
+
+/* Every CAN-USB device exports the dev_get_can_channel_id()/dev_set_can_channel_id()
+ * operations. They are used here to set the new user defined CAN channel ID.
+ */
+int peak_usb_set_eeprom(struct net_device *netdev,
+			struct ethtool_eeprom *eeprom, u8 *data)
+{
+	struct peak_usb_device *dev = netdev_priv(netdev);
+	u32 ch_id;
+	__le32 ch_id_le;
+	int err;
+
+	/* first, read the current user defined CAN channel ID */
+	err = dev->adapter->dev_get_can_channel_id(dev, &ch_id);
+	if (err) {
+		netdev_err(netdev, "Failed to init CAN channel id (err %d)\n", err);
+		return err;
+	}
+
+	/* do update the value with user given bytes.
+	 * ethtool operates on individual bytes. The byte order of the CAN
+	 * channel ID in memory depends on the kernel architecture. We
+	 * convert the CAN channel ID back to the native byte order of the PEAK
+	 * device itself to ensure that the order is consistent for all
+	 * host architectures.
+	 */
+	ch_id_le = cpu_to_le32(ch_id);
+	memcpy((u8 *)&ch_id_le + eeprom->offset, data, eeprom->len);
+	ch_id = le32_to_cpu(ch_id_le);
+
+	/* flash the new value now */
+	err = dev->adapter->dev_set_can_channel_id(dev, ch_id);
+	if (err) {
+		netdev_err(netdev, "Failed to write new CAN channel id (err %d)\n",
+			   err);
+		return err;
+	}
+
+	/* update cached value with the new one */
+	dev->can_channel_id = ch_id;
+
+	return 0;
+}
+
 int pcan_get_ts_info(struct net_device *dev, struct ethtool_ts_info *info)
 {
 	info->so_timestamping =

drivers/net/can/usb/peak_usb/pcan_usb_core.h

@@ -149,4 +149,10 @@ void peak_usb_async_complete(struct urb *urb);
 void peak_usb_restart_complete(struct peak_usb_device *dev);
 int pcan_get_ts_info(struct net_device *dev, struct ethtool_ts_info *info);
 
+/* common 32-bit CAN channel ID ethtool management */
+int peak_usb_get_eeprom_len(struct net_device *netdev);
+int peak_usb_get_eeprom(struct net_device *netdev,
+			struct ethtool_eeprom *eeprom, u8 *data);
+int peak_usb_set_eeprom(struct net_device *netdev,
+			struct ethtool_eeprom *eeprom, u8 *data);
 #endif

drivers/net/can/usb/peak_usb/pcan_usb_fd.c

@@ -1124,6 +1124,9 @@ static int pcan_usb_fd_set_phys_id(struct net_device *netdev,
 static const struct ethtool_ops pcan_usb_fd_ethtool_ops = {
 	.set_phys_id = pcan_usb_fd_set_phys_id,
 	.get_ts_info = pcan_get_ts_info,
+	.get_eeprom_len	= peak_usb_get_eeprom_len,
+	.get_eeprom = peak_usb_get_eeprom,
+	.set_eeprom = peak_usb_set_eeprom,
 };
 
 /* describes the PCAN-USB FD adapter */

drivers/net/can/usb/peak_usb/pcan_usb_pro.c

@@ -1037,6 +1037,9 @@ static int pcan_usb_pro_set_phys_id(struct net_device *netdev,
 static const struct ethtool_ops pcan_usb_pro_ethtool_ops = {
 	.set_phys_id = pcan_usb_pro_set_phys_id,
 	.get_ts_info = pcan_get_ts_info,
+	.get_eeprom_len	= peak_usb_get_eeprom_len,
+	.get_eeprom = peak_usb_get_eeprom,
+	.set_eeprom = peak_usb_set_eeprom,
 };
 
 /*