[PATCH net-next v2 11/12] net: mctp: usb: enable v1.1 packet spanning

[Jeremy Kerr <jk@codeconstruct.com.au>]

Now that mctp-usblib supports DSP0283 v1.1 packet spanning, enable it in
our host-side transport driver.

Add a match for the new device subclass (0x02), and indicating spanning
mode to the usblib rx/tx implementation.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
---
 drivers/net/mctp/mctp-usb.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/net/mctp/mctp-usb.c b/drivers/net/mctp/mctp-usb.c
index e071c2f6daea..4bf5546d520c 100644
--- a/drivers/net/mctp/mctp-usb.c
+++ b/drivers/net/mctp/mctp-usb.c
@@ -3,9 +3,9 @@
  * mctp-usb.c - MCTP-over-USB (DMTF DSP0283) transport binding driver.
  *
  * DSP0283 is available at:
- * https://www.dmtf.org/sites/default/files/standards/documents/DSP0283_1.0.1.pdf
+ * https://www.dmtf.org/sites/default/files/standards/documents/DSP0283_1.1.0.pdf
  *
- * Copyright (C) 2024-2025 Code Construct Pty Ltd
+ * Copyright (C) 2024-2026 Code Construct Pty Ltd
  */
 
 #include <linux/module.h>
@@ -22,6 +22,7 @@
 struct mctp_usb {
 	struct usb_device *usbdev;
 	struct usb_interface *intf;
+	bool span;
 
 	struct net_device *netdev;
 
@@ -40,6 +41,11 @@ struct mctp_usb {
 	struct usb_anchor tx_anchor;
 };
 
+enum {
+	MCTP_USB_SUBCLASS_BASE = 0x00,
+	MCTP_USB_SUBCLASS_SPAN = 0x02,
+};
+
 static void mctp_usb_out_complete(struct urb *urb)
 {
 	struct mctp_usblib_tx_ctx *tx_ctx = urb->context;
@@ -68,6 +74,9 @@ static int mctp_usb_tx_send(struct mctp_usblib_tx_ctx *tx_ctx,
 			  usb_sndbulkpipe(mctp_usb->usbdev, mctp_usb->ep_out),
 			  data, len, mctp_usb_out_complete, tx_ctx);
 
+	if (mctp_usb->span)
+		urb->transfer_flags |= URB_ZERO_PACKET;
+
 	netif_stop_queue(mctp_usb->netdev);
 
 	usb_anchor_urb(urb, &mctp_usb->tx_anchor);
@@ -246,6 +255,7 @@ static int mctp_usb_probe(struct usb_interface *intf,
 	struct usb_host_interface *iface_desc;
 	struct net_device *netdev;
 	struct mctp_usb *dev;
+	bool span;
 	int rc;
 
 	/* only one alternate */
@@ -257,6 +267,8 @@ static int mctp_usb_probe(struct usb_interface *intf,
 		return rc;
 	}
 
+	span = iface_desc->desc.bInterfaceSubClass == MCTP_USB_SUBCLASS_SPAN;
+
 	netdev = alloc_netdev(sizeof(*dev), "mctpusb%d", NET_NAME_ENUM,
 			      mctp_usb_netdev_setup);
 	if (!netdev)
@@ -264,14 +276,17 @@ static int mctp_usb_probe(struct usb_interface *intf,
 
 	SET_NETDEV_DEV(netdev, &intf->dev);
 	dev = netdev_priv(netdev);
+	dev->span = span;
 	dev->netdev = netdev;
 	dev->usbdev = interface_to_usbdev(intf);
 	dev->intf = intf;
+	if (dev->span)
+		netdev->max_mtu = MCTP_USB_1_1_MTU_MAX;
 	spin_lock_init(&dev->rx_lock);
 	usb_set_intfdata(intf, dev);
 
-	mctp_usblib_rx_init(&dev->rx, false);
-	mctp_usblib_tx_init(&dev->tx, &tx_ops, dev, false);
+	mctp_usblib_rx_init(&dev->rx, dev->span);
+	mctp_usblib_tx_init(&dev->tx, &tx_ops, dev, dev->span);
 	init_usb_anchor(&dev->tx_anchor);
 
 	dev->ep_in = ep_in->bEndpointAddress;
@@ -312,7 +327,8 @@ static void mctp_usb_disconnect(struct usb_interface *intf)
 }
 
 static const struct usb_device_id mctp_usb_devices[] = {
-	{ USB_INTERFACE_INFO(USB_CLASS_MCTP, 0x0, 0x1) },
+	{ USB_INTERFACE_INFO(USB_CLASS_MCTP, MCTP_USB_SUBCLASS_BASE, 0x1) },
+	{ USB_INTERFACE_INFO(USB_CLASS_MCTP, MCTP_USB_SUBCLASS_SPAN, 0x1) },
 	{ 0 },
 };
 

-- 
2.47.3