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net: mctp: Add MCTP USB transport driver
Add an implementation for DMTF DSP0283, which defines a MCTP-over-USB
transport. As per that spec, we're restricted to full speed mode,
requiring 512-byte transfers.
Each MCTP-over-USB interface is a peer-to-peer link to a single MCTP
endpoint, so no physical addressing is required (of course, that MCTP
endpoint may then bridge to further MCTP endpoints). Consequently,
interfaces will report with no lladdr data:
# mctp link
dev lo index 1 address 00:00:00:00:00:00 net 1 mtu 65536 up
dev mctpusb0 index 6 address none net 1 mtu 68 up
This is a simple initial implementation, with single rx & tx urbs, and
no multi-packet tx transfers - although we do accept multi-packet rx
from the device.
Includes suggested fixes from Santosh Puranik <spuranik@nvidia.com>.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Cc: Santosh Puranik <spuranik@nvidia.com>
Link: https://patch.msgid.link/20250221-dev-mctp-usb-v3-2-3353030fe9cc@codeconstruct.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jeremy Kerr
Jakub Kicinski
parent
dcc35baae7
commit
0791c0327a
3 changed files with 396 additions and 0 deletions
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@ -47,6 +47,16 @@ config MCTP_TRANSPORT_I3C
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A MCTP protocol network device is created for each I3C bus
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A MCTP protocol network device is created for each I3C bus
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having a "mctp-controller" devicetree property.
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having a "mctp-controller" devicetree property.
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config MCTP_TRANSPORT_USB
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tristate "MCTP USB transport"
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depends on USB
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help
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Provides a driver to access MCTP devices over USB transport,
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defined by DMTF specification DSP0283.
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MCTP-over-USB interfaces are peer-to-peer, so each interface
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represents a physical connection to one remote MCTP endpoint.
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endmenu
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endmenu
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endif
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endif
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@ -1,3 +1,4 @@
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obj-$(CONFIG_MCTP_SERIAL) += mctp-serial.o
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obj-$(CONFIG_MCTP_SERIAL) += mctp-serial.o
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obj-$(CONFIG_MCTP_TRANSPORT_I2C) += mctp-i2c.o
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obj-$(CONFIG_MCTP_TRANSPORT_I2C) += mctp-i2c.o
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obj-$(CONFIG_MCTP_TRANSPORT_I3C) += mctp-i3c.o
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obj-$(CONFIG_MCTP_TRANSPORT_I3C) += mctp-i3c.o
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obj-$(CONFIG_MCTP_TRANSPORT_USB) += mctp-usb.o
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385
drivers/net/mctp/mctp-usb.c
Normal file
385
drivers/net/mctp/mctp-usb.c
Normal file
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@ -0,0 +1,385 @@
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// SPDX-License-Identifier: GPL-2.0
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/*
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* mctp-usb.c - MCTP-over-USB (DMTF DSP0283) transport binding driver.
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*
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* DSP0283 is available at:
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* https://www.dmtf.org/sites/default/files/standards/documents/DSP0283_1.0.1.pdf
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*
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* Copyright (C) 2024-2025 Code Construct Pty Ltd
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*/
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#include <linux/module.h>
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#include <linux/netdevice.h>
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#include <linux/usb.h>
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#include <linux/usb/mctp-usb.h>
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#include <net/mctp.h>
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#include <net/mctpdevice.h>
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#include <net/pkt_sched.h>
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#include <uapi/linux/if_arp.h>
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struct mctp_usb {
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struct usb_device *usbdev;
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struct usb_interface *intf;
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bool stopped;
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struct net_device *netdev;
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u8 ep_in;
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u8 ep_out;
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struct urb *tx_urb;
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struct urb *rx_urb;
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struct delayed_work rx_retry_work;
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};
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static void mctp_usb_out_complete(struct urb *urb)
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{
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struct sk_buff *skb = urb->context;
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struct net_device *netdev = skb->dev;
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int status;
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status = urb->status;
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switch (status) {
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case -ENOENT:
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case -ECONNRESET:
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case -ESHUTDOWN:
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case -EPROTO:
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dev_dstats_tx_dropped(netdev);
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break;
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case 0:
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dev_dstats_tx_add(netdev, skb->len);
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netif_wake_queue(netdev);
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consume_skb(skb);
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return;
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default:
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netdev_dbg(netdev, "unexpected tx urb status: %d\n", status);
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dev_dstats_tx_dropped(netdev);
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}
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kfree_skb(skb);
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}
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static netdev_tx_t mctp_usb_start_xmit(struct sk_buff *skb,
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struct net_device *dev)
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{
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struct mctp_usb *mctp_usb = netdev_priv(dev);
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struct mctp_usb_hdr *hdr;
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unsigned int plen;
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struct urb *urb;
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int rc;
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plen = skb->len;
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if (plen + sizeof(*hdr) > MCTP_USB_XFER_SIZE)
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goto err_drop;
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rc = skb_cow_head(skb, sizeof(*hdr));
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if (rc)
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goto err_drop;
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hdr = skb_push(skb, sizeof(*hdr));
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if (!hdr)
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goto err_drop;
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hdr->id = cpu_to_be16(MCTP_USB_DMTF_ID);
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hdr->rsvd = 0;
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hdr->len = plen + sizeof(*hdr);
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urb = mctp_usb->tx_urb;
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usb_fill_bulk_urb(urb, mctp_usb->usbdev,
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usb_sndbulkpipe(mctp_usb->usbdev, mctp_usb->ep_out),
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skb->data, skb->len,
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mctp_usb_out_complete, skb);
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rc = usb_submit_urb(urb, GFP_ATOMIC);
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if (rc)
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goto err_drop;
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else
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netif_stop_queue(dev);
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return NETDEV_TX_OK;
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err_drop:
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dev_dstats_tx_dropped(dev);
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kfree_skb(skb);
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return NETDEV_TX_OK;
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}
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static void mctp_usb_in_complete(struct urb *urb);
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/* If we fail to queue an in urb atomically (either due to skb allocation or
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* urb submission), we will schedule a rx queue in nonatomic context
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* after a delay, specified in jiffies
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*/
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static const unsigned long RX_RETRY_DELAY = HZ / 4;
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static int mctp_usb_rx_queue(struct mctp_usb *mctp_usb, gfp_t gfp)
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{
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struct sk_buff *skb;
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int rc;
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skb = __netdev_alloc_skb(mctp_usb->netdev, MCTP_USB_XFER_SIZE, gfp);
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if (!skb) {
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rc = -ENOMEM;
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goto err_retry;
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}
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usb_fill_bulk_urb(mctp_usb->rx_urb, mctp_usb->usbdev,
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usb_rcvbulkpipe(mctp_usb->usbdev, mctp_usb->ep_in),
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skb->data, MCTP_USB_XFER_SIZE,
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mctp_usb_in_complete, skb);
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rc = usb_submit_urb(mctp_usb->rx_urb, gfp);
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if (rc) {
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netdev_dbg(mctp_usb->netdev, "rx urb submit failure: %d\n", rc);
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kfree_skb(skb);
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if (rc == -ENOMEM)
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goto err_retry;
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}
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return rc;
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err_retry:
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schedule_delayed_work(&mctp_usb->rx_retry_work, RX_RETRY_DELAY);
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return rc;
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}
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static void mctp_usb_in_complete(struct urb *urb)
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{
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struct sk_buff *skb = urb->context;
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struct net_device *netdev = skb->dev;
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struct mctp_usb *mctp_usb = netdev_priv(netdev);
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struct mctp_skb_cb *cb;
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unsigned int len;
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int status;
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status = urb->status;
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switch (status) {
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case -ENOENT:
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case -ECONNRESET:
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case -ESHUTDOWN:
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case -EPROTO:
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kfree_skb(skb);
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return;
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case 0:
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break;
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default:
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netdev_dbg(netdev, "unexpected rx urb status: %d\n", status);
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kfree_skb(skb);
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return;
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}
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len = urb->actual_length;
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__skb_put(skb, len);
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while (skb) {
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struct sk_buff *skb2 = NULL;
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struct mctp_usb_hdr *hdr;
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u8 pkt_len; /* length of MCTP packet, no USB header */
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hdr = skb_pull_data(skb, sizeof(*hdr));
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if (!hdr)
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break;
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if (be16_to_cpu(hdr->id) != MCTP_USB_DMTF_ID) {
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netdev_dbg(netdev, "rx: invalid id %04x\n",
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be16_to_cpu(hdr->id));
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break;
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}
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if (hdr->len <
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sizeof(struct mctp_hdr) + sizeof(struct mctp_usb_hdr)) {
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netdev_dbg(netdev, "rx: short packet (hdr) %d\n",
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hdr->len);
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break;
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}
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/* we know we have at least sizeof(struct mctp_usb_hdr) here */
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pkt_len = hdr->len - sizeof(struct mctp_usb_hdr);
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if (pkt_len > skb->len) {
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netdev_dbg(netdev,
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"rx: short packet (xfer) %d, actual %d\n",
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hdr->len, skb->len);
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break;
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}
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if (pkt_len < skb->len) {
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/* more packets may follow - clone to a new
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* skb to use on the next iteration
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*/
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skb2 = skb_clone(skb, GFP_ATOMIC);
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if (skb2) {
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if (!skb_pull(skb2, pkt_len)) {
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kfree_skb(skb2);
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skb2 = NULL;
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}
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}
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skb_trim(skb, pkt_len);
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}
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dev_dstats_rx_add(netdev, skb->len);
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skb->protocol = htons(ETH_P_MCTP);
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skb_reset_network_header(skb);
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cb = __mctp_cb(skb);
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cb->halen = 0;
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netif_rx(skb);
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skb = skb2;
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}
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if (skb)
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kfree_skb(skb);
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mctp_usb_rx_queue(mctp_usb, GFP_ATOMIC);
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}
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static void mctp_usb_rx_retry_work(struct work_struct *work)
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{
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struct mctp_usb *mctp_usb = container_of(work, struct mctp_usb,
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rx_retry_work.work);
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if (READ_ONCE(mctp_usb->stopped))
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return;
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mctp_usb_rx_queue(mctp_usb, GFP_KERNEL);
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}
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static int mctp_usb_open(struct net_device *dev)
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{
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struct mctp_usb *mctp_usb = netdev_priv(dev);
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WRITE_ONCE(mctp_usb->stopped, false);
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return mctp_usb_rx_queue(mctp_usb, GFP_KERNEL);
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}
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static int mctp_usb_stop(struct net_device *dev)
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{
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struct mctp_usb *mctp_usb = netdev_priv(dev);
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netif_stop_queue(dev);
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/* prevent RX submission retry */
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WRITE_ONCE(mctp_usb->stopped, true);
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usb_kill_urb(mctp_usb->rx_urb);
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usb_kill_urb(mctp_usb->tx_urb);
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cancel_delayed_work_sync(&mctp_usb->rx_retry_work);
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return 0;
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}
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static const struct net_device_ops mctp_usb_netdev_ops = {
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.ndo_start_xmit = mctp_usb_start_xmit,
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.ndo_open = mctp_usb_open,
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.ndo_stop = mctp_usb_stop,
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};
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static void mctp_usb_netdev_setup(struct net_device *dev)
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{
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dev->type = ARPHRD_MCTP;
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dev->mtu = MCTP_USB_MTU_MIN;
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dev->min_mtu = MCTP_USB_MTU_MIN;
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dev->max_mtu = MCTP_USB_MTU_MAX;
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dev->hard_header_len = sizeof(struct mctp_usb_hdr);
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dev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
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dev->flags = IFF_NOARP;
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dev->netdev_ops = &mctp_usb_netdev_ops;
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dev->pcpu_stat_type = NETDEV_PCPU_STAT_DSTATS;
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}
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static int mctp_usb_probe(struct usb_interface *intf,
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const struct usb_device_id *id)
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{
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struct usb_endpoint_descriptor *ep_in, *ep_out;
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struct usb_host_interface *iface_desc;
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struct net_device *netdev;
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struct mctp_usb *dev;
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int rc;
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/* only one alternate */
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iface_desc = intf->cur_altsetting;
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rc = usb_find_common_endpoints(iface_desc, &ep_in, &ep_out, NULL, NULL);
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if (rc) {
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dev_err(&intf->dev, "invalid endpoints on device?\n");
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return rc;
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}
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netdev = alloc_netdev(sizeof(*dev), "mctpusb%d", NET_NAME_ENUM,
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mctp_usb_netdev_setup);
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if (!netdev)
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return -ENOMEM;
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SET_NETDEV_DEV(netdev, &intf->dev);
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dev = netdev_priv(netdev);
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dev->netdev = netdev;
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dev->usbdev = usb_get_dev(interface_to_usbdev(intf));
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dev->intf = intf;
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usb_set_intfdata(intf, dev);
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dev->ep_in = ep_in->bEndpointAddress;
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dev->ep_out = ep_out->bEndpointAddress;
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dev->tx_urb = usb_alloc_urb(0, GFP_KERNEL);
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dev->rx_urb = usb_alloc_urb(0, GFP_KERNEL);
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if (!dev->tx_urb || !dev->rx_urb) {
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rc = -ENOMEM;
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||||||
|
goto err_free_urbs;
|
||||||
|
}
|
||||||
|
|
||||||
|
INIT_DELAYED_WORK(&dev->rx_retry_work, mctp_usb_rx_retry_work);
|
||||||
|
|
||||||
|
rc = mctp_register_netdev(netdev, NULL, MCTP_PHYS_BINDING_USB);
|
||||||
|
if (rc)
|
||||||
|
goto err_free_urbs;
|
||||||
|
|
||||||
|
return 0;
|
||||||
|
|
||||||
|
err_free_urbs:
|
||||||
|
usb_free_urb(dev->tx_urb);
|
||||||
|
usb_free_urb(dev->rx_urb);
|
||||||
|
free_netdev(netdev);
|
||||||
|
return rc;
|
||||||
|
}
|
||||||
|
|
||||||
|
static void mctp_usb_disconnect(struct usb_interface *intf)
|
||||||
|
{
|
||||||
|
struct mctp_usb *dev = usb_get_intfdata(intf);
|
||||||
|
|
||||||
|
mctp_unregister_netdev(dev->netdev);
|
||||||
|
usb_free_urb(dev->tx_urb);
|
||||||
|
usb_free_urb(dev->rx_urb);
|
||||||
|
usb_put_dev(dev->usbdev);
|
||||||
|
free_netdev(dev->netdev);
|
||||||
|
}
|
||||||
|
|
||||||
|
static const struct usb_device_id mctp_usb_devices[] = {
|
||||||
|
{ USB_INTERFACE_INFO(USB_CLASS_MCTP, 0x0, 0x1) },
|
||||||
|
{ 0 },
|
||||||
|
};
|
||||||
|
|
||||||
|
MODULE_DEVICE_TABLE(usb, mctp_usb_devices);
|
||||||
|
|
||||||
|
static struct usb_driver mctp_usb_driver = {
|
||||||
|
.name = "mctp-usb",
|
||||||
|
.id_table = mctp_usb_devices,
|
||||||
|
.probe = mctp_usb_probe,
|
||||||
|
.disconnect = mctp_usb_disconnect,
|
||||||
|
};
|
||||||
|
|
||||||
|
module_usb_driver(mctp_usb_driver)
|
||||||
|
|
||||||
|
MODULE_LICENSE("GPL");
|
||||||
|
MODULE_AUTHOR("Jeremy Kerr <jk@codeconstruct.com.au>");
|
||||||
|
MODULE_DESCRIPTION("MCTP USB transport");
|
||||||
Loading…
Reference in a new issue