Hi Matias, thank you for the patch.
On Wed, Oct 29, 2025 at 06:40:45PM +0100, Matias Ezequiel Vara Larsen wrote: > Add virtio CAN driver based on Virtio 1.4 specification (see > https://github.com/oasis-tcs/virtio-spec/tree/virtio-1.4). The driver > implements a complete CAN bus interface over Virtio transport, > supporting both CAN Classic and CAN-FD Ids. In term of frames, it > supports classic and CAN FD. RTR frames are only supported with classic > CAN. In the mean time, virtio spec 1.4 got merged to master! :) > > Usage: > - "ip link set up can0" - start controller > - "ip link set down can0" - stop controller > - "candump can0" - receive frames > - "cansend can0 123#DEADBEEF" - send frames > > Signed-off-by: Harald Mommer <[email protected]> > Signed-off-by: Mikhail Golubev-Ciuchea > <[email protected]> > Co-developed-by: Marc Kleine-Budde <[email protected]> > Signed-off-by: Marc Kleine-Budde <[email protected]> > Cc: Damir Shaikhutdinov <[email protected]> > Signed-off-by: Matias Ezequiel Vara Larsen <[email protected]> > --- > V6: > * Address nits (see > > https://lore.kernel.org/all/aO0JjDGk2zLlzB1E@fedora/T/#mc7221192856d557da9c0da2b47e4343dfea0ca2f) > * Check for error during register_virtio_can() > * Remove virtio_device_ready() > * Allocate virtio_can_rx rpkt[] at probe > * Define virtio_can_control struct > * Return VIRTIO_CAN_RESULT_NOT_OK after unlocking > * Define sdu[] as a flex array for both tx and rx. For rx, use > VIRTIO_CAN_F_CAN_FD to figure out the max len for sdu > * Fix statistics in virtio_can_read_tx_queue() and > how we indicate error to the user when getting > VIRTIO_CAN_RESULT_NOT_OK > * Fix syntax of virtio_find_vqs() > * Drop tx_list > * Fix values of VIRTIO_CAN_F_LATE_TX_ACK and VIRTIO_CAN_F_RTR_FRAMES > * Tested with vhost-device-can > (see > https://github.com/rust-vmm/vhost-device/tree/main/vhost-device-can) > and qemu (see > https://github.com/virtualopensystems/qemu/tree/vhu-can-rfc) > > V5: > * Re-base on top of linux-next (next-20240103) > * Tested with https://github.com/OpenSynergy/qemu/tree/virtio-can-spec-rfc-v3 > > RFC V4: > * Apply reverse Christmas tree style > * Add member *classic_dlc to RX and TX CAN frames > * Fix race causing a NETDEV_TX_BUSY return > * Fix TX queue going stuck on -ENOMEM > * Update stats.tx_dropped on kzalloc() failure > * Replace "(err != 0)" with "(unlikely(err))" > * Use "ARRAY_SIZE(sgs)" > * Refactor SGs in virtio_can_send_ctrl_msg() > * Tested with https://github.com/OpenSynergy/qemu/tree/virtio-can-spec-rfc-v3 > > RFC V3: > * Incorporate patch "[PATCH] can: virtio-can: cleanups" from > > https://lore.kernel.org/all/[email protected]/ > * Add missing can_free_echo_skb() > * Replace home-brewed ID allocator with the standard one from kernel > * Simplify flow control > * Tested with https://github.com/OpenSynergy/qemu/tree/virtio-can-spec-rfc-v3 > > RFC V2: > * Remove the event indication queue and use the config space instead, to > indicate a bus off condition > * Rework RX and TX messages having a length field and some more fields for CAN > EXT > --- > MAINTAINERS | 7 + > drivers/net/can/Kconfig | 12 + > drivers/net/can/Makefile | 1 + > drivers/net/can/virtio_can.c | 1022 +++++++++++++++++++++++++++++++ > include/uapi/linux/virtio_can.h | 78 +++ > 5 files changed, 1120 insertions(+) > create mode 100644 drivers/net/can/virtio_can.c > create mode 100644 include/uapi/linux/virtio_can.h > > diff --git a/MAINTAINERS b/MAINTAINERS > index 80cd3498c293..14a738b8ecb2 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -27068,6 +27068,13 @@ F: drivers/scsi/virtio_scsi.c > F: include/uapi/linux/virtio_blk.h > F: include/uapi/linux/virtio_scsi.h > > +VIRTIO CAN DRIVER > +M: "Harald Mommer" <[email protected]> > +L: [email protected] > +S: Maintained > +F: drivers/net/can/virtio_can.c > +F: include/uapi/linux/virtio_can.h > + > VIRTIO CONSOLE DRIVER > M: Amit Shah <[email protected]> > L: [email protected] > diff --git a/drivers/net/can/Kconfig b/drivers/net/can/Kconfig > index d43d56694667..7b5806f11853 100644 > --- a/drivers/net/can/Kconfig > +++ b/drivers/net/can/Kconfig > @@ -217,6 +217,18 @@ config CAN_XILINXCAN > Xilinx CAN driver. This driver supports both soft AXI CAN IP and > Zynq CANPS IP. > > +config CAN_VIRTIO_CAN > + depends on VIRTIO > + tristate "Virtio CAN device support" > + default n > + help > + Say Y here if you want to support for Virtio CAN. > + > + To compile this driver as a module, choose M here: the > + module will be called virtio-can. > + > + If unsure, say N. > + > source "drivers/net/can/c_can/Kconfig" > source "drivers/net/can/cc770/Kconfig" > source "drivers/net/can/ctucanfd/Kconfig" > diff --git a/drivers/net/can/Makefile b/drivers/net/can/Makefile > index 56138d8ddfd2..2ddea733ed5d 100644 > --- a/drivers/net/can/Makefile > +++ b/drivers/net/can/Makefile > @@ -32,6 +32,7 @@ obj-$(CONFIG_CAN_PEAK_PCIEFD) += peak_canfd/ > obj-$(CONFIG_CAN_SJA1000) += sja1000/ > obj-$(CONFIG_CAN_SUN4I) += sun4i_can.o > obj-$(CONFIG_CAN_TI_HECC) += ti_hecc.o > +obj-$(CONFIG_CAN_VIRTIO_CAN) += virtio_can.o > obj-$(CONFIG_CAN_XILINXCAN) += xilinx_can.o > > subdir-ccflags-$(CONFIG_CAN_DEBUG_DEVICES) += -DDEBUG > diff --git a/drivers/net/can/virtio_can.c b/drivers/net/can/virtio_can.c > new file mode 100644 > index 000000000000..a66fd4fa8393 > --- /dev/null > +++ b/drivers/net/can/virtio_can.c > @@ -0,0 +1,1022 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * CAN bus driver for the Virtio CAN controller > + * > + * Copyright (C) 2021-2023 OpenSynergy GmbH > + * Copyright Red Hat, Inc. 2025 > + */ > + > +#include <linux/atomic.h> > +#include <linux/idr.h> > +#include <linux/interrupt.h> > +#include <linux/io.h> > +#include <linux/kernel.h> > +#include <linux/module.h> > +#include <linux/mutex.h> > +#include <linux/netdevice.h> > +#include <linux/stddef.h> > +#include <linux/can/dev.h> > +#include <linux/virtio.h> > +#include <linux/virtio_ring.h> > +#include <linux/virtio_can.h> > + > +/* CAN device queues */ > +#define VIRTIO_CAN_QUEUE_TX 0 /* Driver side view! The device receives here > */ > +#define VIRTIO_CAN_QUEUE_RX 1 /* Driver side view! The device transmits here > */ > +#define VIRTIO_CAN_QUEUE_CONTROL 2 > +#define VIRTIO_CAN_QUEUE_COUNT 3 > + > +#define CAN_KNOWN_FLAGS \ > + (VIRTIO_CAN_FLAGS_EXTENDED |\ > + VIRTIO_CAN_FLAGS_FD |\ > + VIRTIO_CAN_FLAGS_RTR) > + > +/* Max. number of in flight TX messages */ > +#define VIRTIO_CAN_ECHO_SKB_MAX 128 > + > +struct virtio_can_tx { > + unsigned int putidx; > + struct virtio_can_tx_in tx_in; > + /* Keep virtio_can_tx_out at the end of the structure due to flex array > */ > + struct virtio_can_tx_out tx_out; > +}; > + > +struct virtio_can_control { > + struct virtio_can_control_out cpkt_out; > + struct virtio_can_control_in cpkt_in; > +}; > + > +/* virtio_can private data structure */ > +struct virtio_can_priv { > + struct can_priv can; /* must be the first member */ > + /* NAPI for RX messages */ > + struct napi_struct napi; > + /* NAPI for TX messages */ > + struct napi_struct napi_tx; > + /* The network device we're associated with */ > + struct net_device *dev; > + /* The virtio device we're associated with */ > + struct virtio_device *vdev; > + /* The virtqueues */ > + struct virtqueue *vqs[VIRTIO_CAN_QUEUE_COUNT]; > + /* I/O callback function pointers for the virtqueues */ > + vq_callback_t *io_callbacks[VIRTIO_CAN_QUEUE_COUNT]; These appears not to be really used - they are set inside virtio_can_find_vqs(), but then nothing uses them. > + /* Lock for TX operations */ > + spinlock_t tx_lock; > + /* Control queue lock. Defensive programming, may be not needed */ > + struct mutex ctrl_lock; > + /* Wait for control queue processing without polling */ > + struct completion ctrl_done; > + /* Array of receive queue messages */ > + struct virtio_can_rx *rpkt; > + struct virtio_can_control can_ctr_msg; > + /* Data to get and maintain the putidx for local TX echo */ > + struct ida tx_putidx_ida; > + /* In flight TX messages */ > + atomic_t tx_inflight; > + /* SDU length */ > + int sdu_len; > + /* BusOff pending. Reset after successful indication to upper layer */ > + bool busoff_pending; > +}; > + > +/* Function copied from virtio_net.c */ > +static void virtqueue_napi_schedule(struct napi_struct *napi, > + struct virtqueue *vq) > +{ > + if (napi_schedule_prep(napi)) { > + virtqueue_disable_cb(vq); > + __napi_schedule(napi); > + } > +} > + > +/* Function copied from virtio_net.c */ > +static void virtqueue_napi_complete(struct napi_struct *napi, > + struct virtqueue *vq, int processed) > +{ > + int opaque; > + > + opaque = virtqueue_enable_cb_prepare(vq); > + if (napi_complete_done(napi, processed)) { > + if (unlikely(virtqueue_poll(vq, opaque))) > + virtqueue_napi_schedule(napi, vq); > + } else { > + virtqueue_disable_cb(vq); > + } > +} > + > +static void virtio_can_free_candev(struct net_device *ndev) > +{ > + struct virtio_can_priv *priv = netdev_priv(ndev); > + > + ida_destroy(&priv->tx_putidx_ida); > + free_candev(ndev); > +} > + > +static int virtio_can_alloc_tx_idx(struct virtio_can_priv *priv) > +{ > + int tx_idx; > + > + tx_idx = ida_alloc_range(&priv->tx_putidx_ida, 0, > + priv->can.echo_skb_max - 1, GFP_KERNEL); > + if (tx_idx >= 0) > + atomic_inc(&priv->tx_inflight); > + > + return tx_idx; > +} > + > +static void virtio_can_free_tx_idx(struct virtio_can_priv *priv, > + unsigned int idx) > +{ > + ida_free(&priv->tx_putidx_ida, idx); > + atomic_dec(&priv->tx_inflight); > +} > + > +/* Create a scatter-gather list representing our input buffer and put > + * it in the queue. > + * > + * Callers should take appropriate locks. No caller is taking any lock. > + */ > +static int virtio_can_add_inbuf(struct virtqueue *vq, void *buf, > + unsigned int size) > +{ > + struct scatterlist sg[1]; > + int ret; > + > + sg_init_one(sg, buf, size); > + > + ret = virtqueue_add_inbuf(vq, sg, 1, buf, GFP_ATOMIC); > + virtqueue_kick(vq); > + if (ret == 0) > + ret = vq->num_free; The returned value in case of success (i.e.: vq->num_free) is not used. > + return ret; > +} > + > +/* Send a control message with message type either > + * > + * - VIRTIO_CAN_SET_CTRL_MODE_START or > + * - VIRTIO_CAN_SET_CTRL_MODE_STOP. > + * > + * Unlike AUTOSAR CAN Driver Can_SetControllerMode() there is no requirement > + * for this Linux driver to have an asynchronous implementation of the mode > + * setting function so in order to keep things simple the function is > + * implemented as synchronous function. Design pattern is > + * virtio_console.c/__send_control_msg() & > virtio_net.c/virtnet_send_command(). > + */ Comment is not really helpful nor informative, at least for me. I'd drop the AUTOSAR part at least. > +static u8 virtio_can_send_ctrl_msg(struct net_device *ndev, u16 msg_type) > +{ > + struct scatterlist sg_out, sg_in, *sgs[2] = { &sg_out, &sg_in }; > + struct virtio_can_priv *priv = netdev_priv(ndev); > + struct device *dev = &priv->vdev->dev; > + struct virtqueue *vq; > + unsigned int len; > + int err; > + > + vq = priv->vqs[VIRTIO_CAN_QUEUE_CONTROL]; > + > + /* The function may be serialized by rtnl lock. Not sure. > + * Better safe than sorry. > + */ > + mutex_lock(&priv->ctrl_lock); Consider the newer guard() syntax: guard(mutex)(&priv->ctrl_lock) > + > + priv->can_ctr_msg.cpkt_out.msg_type = cpu_to_le16(msg_type); > + sg_init_one(&sg_out, &priv->can_ctr_msg.cpkt_out, > + sizeof(priv->can_ctr_msg.cpkt_out)); > + sg_init_one(&sg_in, &priv->can_ctr_msg.cpkt_in, > sizeof(priv->can_ctr_msg.cpkt_in)); > + > + err = virtqueue_add_sgs(vq, sgs, 1u, 1u, priv, GFP_ATOMIC); > + if (err != 0) { > + /* Not expected to happen */ > + dev_err(dev, "%s(): virtqueue_add_sgs() failed\n", __func__); > + mutex_unlock(&priv->ctrl_lock); > + return VIRTIO_CAN_RESULT_NOT_OK; > + } > + > + if (!virtqueue_kick(vq)) { > + /* Not expected to happen */ > + dev_err(dev, "%s(): Kick failed\n", __func__); > + mutex_unlock(&priv->ctrl_lock); > + return VIRTIO_CAN_RESULT_NOT_OK; > + } > + > + while (!virtqueue_get_buf(vq, &len) && !virtqueue_is_broken(vq)) > + wait_for_completion(&priv->ctrl_done); > + Since the call is synchronous, does can_ctr_msg really need to be part of priv? Cannot be it allocated from the stack? > + mutex_unlock(&priv->ctrl_lock); > + > + return priv->can_ctr_msg.cpkt_in.result; > +} > + > +static void virtio_can_start(struct net_device *ndev) > +{ > + struct virtio_can_priv *priv = netdev_priv(ndev); > + u8 result; > + > + result = virtio_can_send_ctrl_msg(ndev, VIRTIO_CAN_SET_CTRL_MODE_START); > + if (result != VIRTIO_CAN_RESULT_OK) { > + /* Not expected to happen */ > + netdev_err(ndev, "CAN controller start failed\n"); > + } > + > + priv->busoff_pending = false; > + priv->can.state = CAN_STATE_ERROR_ACTIVE; > + > + /* Switch carrier on if device was not connected to the bus */ > + if (!netif_carrier_ok(ndev)) > + netif_carrier_on(ndev); > +} > + > +/* See also m_can.c/m_can_set_mode() > + * > + * It is interesting that not only the M-CAN implementation but also all > other > + * implementations I looked into only support CAN_MODE_START. > + * That CAN_MODE_SLEEP is frequently not found to be supported anywhere did > not > + * come not as surprise but that CAN_MODE_STOP is also never supported was > one. > + * The function is accessible via the method pointer do_set_mode in > + * struct can_priv. As usual no documentation there. > + * May not play any role as grepping through the code did not reveal any > place > + * from where the method is actually called. > + */ The do_set_mode method is used e.g. to restart the CAN after a bus-off event. > +static int virtio_can_set_mode(struct net_device *dev, enum can_mode mode) > +{ > + switch (mode) { > + case CAN_MODE_START: > + virtio_can_start(dev); > + netif_wake_queue(dev); > + break; > + default: > + return -EOPNOTSUPP; > + } > + > + return 0; > +} > + > +/* Called by issuing "ip link set up can0" */ > +static int virtio_can_open(struct net_device *dev) > +{ > + /* start the virtio_can controller */ > + virtio_can_start(dev); > + > + /* RX and TX napi were already enabled in virtio_can_probe() */ > + netif_start_queue(dev); > + > + return 0; > +} > + > +static void virtio_can_stop(struct net_device *ndev) > +{ > + struct virtio_can_priv *priv = netdev_priv(ndev); > + struct device *dev = &priv->vdev->dev; > + u8 result; > + > + result = virtio_can_send_ctrl_msg(ndev, VIRTIO_CAN_SET_CTRL_MODE_STOP); > + if (result != VIRTIO_CAN_RESULT_OK) > + dev_err(dev, "CAN controller stop failed\n"); > + > + priv->busoff_pending = false; > + priv->can.state = CAN_STATE_STOPPED; > + > + /* Switch carrier off if device was connected to the bus */ > + if (netif_carrier_ok(ndev)) > + netif_carrier_off(ndev); > +} > + > +static int virtio_can_close(struct net_device *dev) > +{ > + netif_stop_queue(dev); > + /* Keep RX napi active to allow dropping of pending RX CAN messages, > + * keep TX napi active to allow processing of cancelled CAN messages > + */ > + virtio_can_stop(dev); > + close_candev(dev); > + > + return 0; > +} > + > +static netdev_tx_t virtio_can_start_xmit(struct sk_buff *skb, > + struct net_device *dev) > +{ > + const unsigned int hdr_size = offsetof(struct virtio_can_tx_out, sdu); > + struct scatterlist sg_out, sg_in, *sgs[2] = { &sg_out, &sg_in }; > + struct canfd_frame *cf = (struct canfd_frame *)skb->data; > + struct virtio_can_priv *priv = netdev_priv(dev); > + netdev_tx_t xmit_ret = NETDEV_TX_OK; > + struct virtio_can_tx *can_tx_msg; > + struct virtqueue *vq; > + unsigned long flags; > + u32 can_flags; > + int putidx; > + int err; > + > + vq = priv->vqs[VIRTIO_CAN_QUEUE_TX]; > + > + if (can_dev_dropped_skb(dev, skb)) > + goto kick; /* No way to return NET_XMIT_DROP here */ > + > + /* No local check for CAN_RTR_FLAG or FD frame against negotiated > + * features. The device will reject those anyway if not supported. > + */ > + > + can_tx_msg = kzalloc(sizeof(*can_tx_msg) + cf->len, GFP_ATOMIC); > + if (!can_tx_msg) { > + dev->stats.tx_dropped++; > + goto kick; /* No way to return NET_XMIT_DROP here */ > + } > + > + can_tx_msg->tx_out.msg_type = cpu_to_le16(VIRTIO_CAN_TX); > + can_flags = 0; > + > + if (cf->can_id & CAN_EFF_FLAG) { > + can_flags |= VIRTIO_CAN_FLAGS_EXTENDED; > + can_tx_msg->tx_out.can_id = cpu_to_le32(cf->can_id & > CAN_EFF_MASK); > + } else { > + can_tx_msg->tx_out.can_id = cpu_to_le32(cf->can_id & > CAN_SFF_MASK); > + } > + if (cf->can_id & CAN_RTR_FLAG) > + can_flags |= VIRTIO_CAN_FLAGS_RTR; > + else > + memcpy(can_tx_msg->tx_out.sdu, cf->data, cf->len); > + if (can_is_canfd_skb(skb)) > + can_flags |= VIRTIO_CAN_FLAGS_FD; > + > + can_tx_msg->tx_out.flags = cpu_to_le32(can_flags); > + can_tx_msg->tx_out.length = cpu_to_le16(cf->len); > + > + /* Prepare sending of virtio message */ > + sg_init_one(&sg_out, &can_tx_msg->tx_out, hdr_size + cf->len); > + sg_init_one(&sg_in, &can_tx_msg->tx_in, sizeof(can_tx_msg->tx_in)); > + > + putidx = virtio_can_alloc_tx_idx(priv); > + > + if (unlikely(putidx < 0)) { > + /* -ENOMEM or -ENOSPC here. -ENOSPC should not be possible as > + * tx_inflight >= can.echo_skb_max is checked in flow control > + */ > + WARN_ON_ONCE(putidx == -ENOSPC); > + kfree(can_tx_msg); > + dev->stats.tx_dropped++; > + goto kick; /* No way to return NET_XMIT_DROP here */ > + } > + > + can_tx_msg->putidx = (unsigned int)putidx; > + > + /* Push loopback echo. Will be looped back on TX interrupt/TX NAPI */ > + can_put_echo_skb(skb, dev, can_tx_msg->putidx, 0); > + > + /* Protect queue and list operations */ > + spin_lock_irqsave(&priv->tx_lock, flags); > + err = virtqueue_add_sgs(vq, sgs, 1u, 1u, can_tx_msg, GFP_ATOMIC); > + if (unlikely(err)) { > + can_free_echo_skb(dev, can_tx_msg->putidx, NULL); > + virtio_can_free_tx_idx(priv, can_tx_msg->putidx); > + spin_unlock_irqrestore(&priv->tx_lock, flags); > + netif_stop_queue(dev); > + kfree(can_tx_msg); > + /* Expected never to be seen */ > + netdev_warn(dev, "TX: Stop queue, err = %d\n", err); > + xmit_ret = NETDEV_TX_BUSY; > + goto kick; > + } > + > + /* Normal flow control: stop queue when no transmission slots left */ > + if (atomic_read(&priv->tx_inflight) >= priv->can.echo_skb_max || > + vq->num_free == 0 || (vq->num_free < ARRAY_SIZE(sgs) && > + !virtio_has_feature(vq->vdev, VIRTIO_RING_F_INDIRECT_DESC))) { > + netif_stop_queue(dev); > + netdev_dbg(dev, "TX: Normal stop queue\n"); > + } > + > + spin_unlock_irqrestore(&priv->tx_lock, flags); > + > +kick: > + if (netif_queue_stopped(dev) || !netdev_xmit_more()) { > + if (!virtqueue_kick(vq)) > + netdev_err(dev, "%s(): Kick failed\n", __func__); > + } > + > + return xmit_ret; > +} > + > +static const struct net_device_ops virtio_can_netdev_ops = { > + .ndo_open = virtio_can_open, > + .ndo_stop = virtio_can_close, > + .ndo_start_xmit = virtio_can_start_xmit, > + .ndo_change_mtu = can_change_mtu, > +}; > + > +static int register_virtio_can_dev(struct net_device *dev) > +{ > + dev->flags |= IFF_ECHO; /* we support local echo */ > + dev->netdev_ops = &virtio_can_netdev_ops; > + > + return register_candev(dev); > +} > + > +/* Compare with m_can.c/m_can_echo_tx_event() */ > +static int virtio_can_read_tx_queue(struct virtqueue *vq) > +{ > + struct virtio_can_priv *can_priv = vq->vdev->priv; > + struct net_device *dev = can_priv->dev; > + struct virtio_can_tx *can_tx_msg; > + struct net_device_stats *stats; > + unsigned long flags; > + unsigned int len; > + u8 result; > + > + stats = &dev->stats; > + > + /* Protect list and virtio queue operations */ > + spin_lock_irqsave(&can_priv->tx_lock, flags); The section below seems a pretty big one to protect behind a spin lock. > + > + can_tx_msg = virtqueue_get_buf(vq, &len); > + if (!can_tx_msg) { > + spin_unlock_irqrestore(&can_priv->tx_lock, flags); > + return 0; /* No more data */ > + } > + > + if (unlikely(len < sizeof(struct virtio_can_tx_in))) { > + netdev_err(dev, "TX ACK: Device sent no result code\n"); > + result = VIRTIO_CAN_RESULT_NOT_OK; /* Keep things going */ > + } else { > + result = can_tx_msg->tx_in.result; > + } > + > + if (can_priv->can.state < CAN_STATE_BUS_OFF) { > + if (result != VIRTIO_CAN_RESULT_OK) { > + struct can_frame *skb_cf; > + struct sk_buff *skb = alloc_can_err_skb(dev, &skb_cf); > + > + if (skb) { > + skb_cf->can_id |= CAN_ERR_CRTL; > + skb_cf->data[1] |= CAN_ERR_CRTL_UNSPEC; > + netif_rx(skb); > + } > + netdev_warn(dev, "TX ACK: Result = %u\n", result); > + can_free_echo_skb(dev, can_tx_msg->putidx, NULL); > + stats->tx_dropped++; > + } else { > + stats->tx_bytes += can_get_echo_skb(dev, > can_tx_msg->putidx, > + NULL); Please check the indentation here. > + stats->tx_packets++; > + } > + } else { > + netdev_dbg(dev, "TX ACK: Controller inactive, drop echo\n"); > + can_free_echo_skb(dev, can_tx_msg->putidx, NULL); > + stats->tx_dropped++; > + } > + > + virtio_can_free_tx_idx(can_priv, can_tx_msg->putidx); > + > + /* Flow control */ > + if (netif_queue_stopped(dev)) { > + netdev_dbg(dev, "TX ACK: Wake up stopped queue\n"); > + netif_wake_queue(dev); > + } > + > + spin_unlock_irqrestore(&can_priv->tx_lock, flags); > + > + kfree(can_tx_msg); > + > + return 1; /* Queue was not empty so there may be more data */ > +} > + > +/* Poll TX used queue for sent CAN messages > + * See https://wiki.linuxfoundation.org/networking/napi function > + * int (*poll)(struct napi_struct *napi, int budget); > + */ > +static int virtio_can_tx_poll(struct napi_struct *napi, int quota) > +{ > + struct net_device *dev = napi->dev; > + struct virtio_can_priv *priv; > + struct virtqueue *vq; > + int work_done = 0; > + > + priv = netdev_priv(dev); > + vq = priv->vqs[VIRTIO_CAN_QUEUE_TX]; > + > + while (work_done < quota && virtio_can_read_tx_queue(vq) != 0) > + work_done++; > + > + if (work_done < quota) > + virtqueue_napi_complete(napi, vq, work_done); > + > + return work_done; > +} > + > +static void virtio_can_tx_intr(struct virtqueue *vq) > +{ > + struct virtio_can_priv *can_priv = vq->vdev->priv; > + > + virtqueue_disable_cb(vq); > + napi_schedule(&can_priv->napi_tx); > +} > + > +/* This function is the NAPI RX poll function and NAPI guarantees that this > + * function is not invoked simultaneously on multiple processors. > + * Read a RX message from the used queue and sends it to the upper layer. > + * (See also m_can.c / m_can_read_fifo()). > + */ > +static int virtio_can_read_rx_queue(struct virtqueue *vq) > +{ > + const unsigned int header_size = offsetof(struct virtio_can_rx, sdu); > + struct virtio_can_priv *priv = vq->vdev->priv; > + struct net_device *dev = priv->dev; > + struct net_device_stats *stats; > + struct virtio_can_rx *can_rx; > + unsigned int transport_len; > + struct canfd_frame *cf; > + struct sk_buff *skb; > + unsigned int len; > + u32 can_flags; > + u16 msg_type; > + u32 can_id; > + > + stats = &dev->stats; > + > + can_rx = virtqueue_get_buf(vq, &transport_len); > + if (!can_rx) > + return 0; /* No more data */ > + > + if (transport_len < header_size) { > + netdev_warn(dev, "RX: Message too small\n"); > + goto putback; > + } > + > + if (priv->can.state >= CAN_STATE_ERROR_PASSIVE) { > + netdev_dbg(dev, "%s(): Controller not active\n", __func__); > + goto putback; > + } > + > + msg_type = le16_to_cpu(can_rx->msg_type); > + if (msg_type != VIRTIO_CAN_RX) { > + netdev_warn(dev, "RX: Got unknown msg_type %04x\n", msg_type); > + goto putback; > + } > + > + len = le16_to_cpu(can_rx->length); > + can_flags = le32_to_cpu(can_rx->flags); > + can_id = le32_to_cpu(can_rx->can_id); > + > + if (can_flags & ~CAN_KNOWN_FLAGS) { > + stats->rx_dropped++; > + netdev_warn(dev, "RX: CAN Id 0x%08x: Invalid flags 0x%x\n", > + can_id, can_flags); > + goto putback; > + } > + > + if (can_flags & VIRTIO_CAN_FLAGS_EXTENDED) { > + can_id &= CAN_EFF_MASK; > + can_id |= CAN_EFF_FLAG; > + } else { > + can_id &= CAN_SFF_MASK; > + } > + > + if (can_flags & VIRTIO_CAN_FLAGS_RTR) { > + if (!virtio_has_feature(vq->vdev, VIRTIO_CAN_F_RTR_FRAMES)) { > + stats->rx_dropped++; > + netdev_warn(dev, "RX: CAN Id 0x%08x: RTR not > negotiated\n", > + can_id); > + goto putback; > + } > + if (can_flags & VIRTIO_CAN_FLAGS_FD) { > + stats->rx_dropped++; > + netdev_warn(dev, "RX: CAN Id 0x%08x: RTR with FD not > possible\n", > + can_id); > + goto putback; > + } > + > + if (len > 0xF) { > + stats->rx_dropped++; > + netdev_warn(dev, "RX: CAN Id 0x%08x: RTR with DLC > > 0xF\n", > + can_id); > + goto putback; > + } > + > + if (len > 0x8) > + len = 0x8; > + > + can_id |= CAN_RTR_FLAG; > + } > + > + if (transport_len < header_size + len) { > + netdev_warn(dev, "RX: Message too small for payload\n"); > + goto putback; > + } > + > + if (can_flags & VIRTIO_CAN_FLAGS_FD) { > + if (!virtio_has_feature(vq->vdev, VIRTIO_CAN_F_CAN_FD)) { > + stats->rx_dropped++; > + netdev_warn(dev, "RX: CAN Id 0x%08x: FD not > negotiated\n", > + can_id); > + goto putback; > + } > + > + if (len > CANFD_MAX_DLEN) > + len = CANFD_MAX_DLEN; > + > + skb = alloc_canfd_skb(priv->dev, &cf); > + } else { > + if (!virtio_has_feature(vq->vdev, VIRTIO_CAN_F_CAN_CLASSIC)) { > + stats->rx_dropped++; > + netdev_warn(dev, "RX: CAN Id 0x%08x: classic not > negotiated\n", > + can_id); > + goto putback; > + } > + > + if (len > CAN_MAX_DLEN) > + len = CAN_MAX_DLEN; > + > + skb = alloc_can_skb(priv->dev, (struct can_frame **)&cf); > + } > + if (!skb) { > + stats->rx_dropped++; > + netdev_warn(dev, "RX: No skb available\n"); > + goto putback; > + } > + > + cf->can_id = can_id; > + cf->len = len; > + if (!(can_flags & VIRTIO_CAN_FLAGS_RTR)) { > + /* RTR frames have a DLC but no payload */ > + memcpy(cf->data, can_rx->sdu, len); > + } > + > + if (netif_receive_skb(skb) == NET_RX_SUCCESS) { > + stats->rx_packets++; > + if (!(can_flags & VIRTIO_CAN_FLAGS_RTR)) > + stats->rx_bytes += cf->len; > + } > + > +putback: > + /* Put processed RX buffer back into avail queue */ > + virtio_can_add_inbuf(vq, can_rx, > + sizeof(struct virtio_can_rx) + priv->sdu_len); > + > + return 1; /* Queue was not empty so there may be more data */ > +} > + > +/* See m_can_poll() / m_can_handle_state_errors() > m_can_handle_state_change() */ > +static int virtio_can_handle_busoff(struct net_device *dev) > +{ > + struct virtio_can_priv *priv = netdev_priv(dev); > + struct can_frame *cf; > + struct sk_buff *skb; > + > + if (!priv->busoff_pending) > + return 0; > + > + if (priv->can.state < CAN_STATE_BUS_OFF) { > + netdev_dbg(dev, "entered error bus off state\n"); > + > + /* bus-off state */ > + priv->can.state = CAN_STATE_BUS_OFF; > + priv->can.can_stats.bus_off++; > + can_bus_off(dev); > + } > + > + /* propagate the error condition to the CAN stack */ > + skb = alloc_can_err_skb(dev, &cf); > + if (unlikely(!skb)) > + return 0; > + > + /* bus-off state */ > + cf->can_id |= CAN_ERR_BUSOFF; > + > + /* Ensure that the BusOff indication does not get lost */ > + if (netif_receive_skb(skb) == NET_RX_SUCCESS) > + priv->busoff_pending = false; > + > + return 1; > +} > + > +/* Poll RX used queue for received CAN messages > + * See https://wiki.linuxfoundation.org/networking/napi function > + * int (*poll)(struct napi_struct *napi, int budget); > + * Important: "The networking subsystem promises that poll() will not be > + * invoked simultaneously (for the same napi_struct) on multiple processors" > + */ > +static int virtio_can_rx_poll(struct napi_struct *napi, int quota) > +{ > + struct net_device *dev = napi->dev; > + struct virtio_can_priv *priv; > + struct virtqueue *vq; > + int work_done = 0; > + > + priv = netdev_priv(dev); > + vq = priv->vqs[VIRTIO_CAN_QUEUE_RX]; > + > + work_done += virtio_can_handle_busoff(dev); > + > + while (work_done < quota && virtio_can_read_rx_queue(vq) != 0) > + work_done++; > + > + if (work_done < quota) > + virtqueue_napi_complete(napi, vq, work_done); > + > + return work_done; > +} > + > +static void virtio_can_rx_intr(struct virtqueue *vq) > +{ > + struct virtio_can_priv *can_priv = vq->vdev->priv; > + > + virtqueue_disable_cb(vq); > + napi_schedule(&can_priv->napi); > +} > + > +static void virtio_can_control_intr(struct virtqueue *vq) > +{ > + struct virtio_can_priv *can_priv = vq->vdev->priv; > + > + complete(&can_priv->ctrl_done); > +} > + > +static void virtio_can_config_changed(struct virtio_device *vdev) > +{ > + struct virtio_can_priv *can_priv = vdev->priv; > + u16 status; > + > + status = virtio_cread16(vdev, offsetof(struct virtio_can_config, > + status)); > + > + if (!(status & VIRTIO_CAN_S_CTRL_BUSOFF)) > + return; > + > + if (!can_priv->busoff_pending && > + can_priv->can.state < CAN_STATE_BUS_OFF) { > + can_priv->busoff_pending = true; > + napi_schedule(&can_priv->napi); > + } > +} > + > +static void virtio_can_populate_rx_vq(struct virtio_device *vdev) > +{ > + struct virtio_can_priv *priv = vdev->priv; > + struct virtqueue *vq; > + struct virtio_can_rx *buf; > + unsigned int idx; > + unsigned int buf_size = sizeof(struct virtio_can_rx) + priv->sdu_len; > + int ret; > + int num_elements; > + > + /* Fill RX queue */ > + vq = priv->vqs[VIRTIO_CAN_QUEUE_RX]; > + num_elements = vq->num_free; > + buf = priv->rpkt; > + > + for (idx = 0; idx < num_elements; idx++) { > + ret = virtio_can_add_inbuf(vq, buf, buf_size); > + if (ret < 0) { > + dev_dbg(&vdev->dev, "rpkt fill: ret=%d, idx=%u, > size=%u\n", > + ret, idx, buf_size);i Here we may have a fatal error on the first element that goes unnoticed if debug is not enabled. Consider to raise the log level or to return an error. Moreover, virtio_can_add_inbuf() kicks the vq virtqueue for each inbuf that is added; other drivers prefer to do it only after all the inbufs have been added, in particular during the init phase [1] [2]. [1] https://elixir.bootlin.com/linux/v6.17.7/source/arch/um/drivers/virtio_pcidev.c#L463 [2] https://elixir.bootlin.com/linux/v6.17.7/source/drivers/virtio/virtio_input.c#L214 > + break; > + } > + buf += buf_size; > + } > + dev_dbg(&vdev->dev, "%u rpkt added\n", idx); > +} > + > +static int virtio_can_find_vqs(struct virtio_can_priv *priv) > +{ > + priv->io_callbacks[VIRTIO_CAN_QUEUE_TX] = virtio_can_tx_intr; > + priv->io_callbacks[VIRTIO_CAN_QUEUE_RX] = virtio_can_rx_intr; > + priv->io_callbacks[VIRTIO_CAN_QUEUE_CONTROL] = virtio_can_control_intr; > + io_callbacks[] elements are then not used, see above. > + /* The order of RX and TX is exactly the opposite as in console and > + * network. Does not play any role but is a bad trap. > + */ > + struct virtqueue_info vqs_info[] = { > + { "can-tx", virtio_can_tx_intr }, > + { "can-rx", virtio_can_rx_intr }, > + { "can-state-ctrl", virtio_can_control_intr }, > + }; > + > + /* Find the queues. */ > + return virtio_find_vqs(priv->vdev, VIRTIO_CAN_QUEUE_COUNT, priv->vqs, > + vqs_info, NULL); > +} > + > +/* Function must not be called before virtio_can_find_vqs() has been run */ > +static void virtio_can_del_vq(struct virtio_device *vdev) > +{ > + struct virtio_can_priv *priv = vdev->priv; > + struct virtqueue *vq; > + > + /* Reset the device */ > + if (vdev->config->reset) > + vdev->config->reset(vdev); > + > + /* From here we have dead silence from the device side so no locks > + * are needed to protect against device side events. > + */ > + > + vq = priv->vqs[VIRTIO_CAN_QUEUE_CONTROL]; > + while (virtqueue_detach_unused_buf(vq)) > + ; /* Do nothing, content allocated statically */ > + > + vq = priv->vqs[VIRTIO_CAN_QUEUE_RX]; > + while (virtqueue_detach_unused_buf(vq)) > + ; /* Do nothing, content allocated statically */ > + > + vq = priv->vqs[VIRTIO_CAN_QUEUE_TX]; > + while (virtqueue_detach_unused_buf(vq)) > + ; /* Do nothing, content to be de-allocated separately */ > + > + if (vdev->config->del_vqs) > + vdev->config->del_vqs(vdev); > +} > + > +/* See virtio_net.c/virtnet_remove() and also m_can.c/m_can_plat_remove() */ > +static void virtio_can_remove(struct virtio_device *vdev) > +{ > + struct virtio_can_priv *priv = vdev->priv; > + struct net_device *dev = priv->dev; > + > + unregister_candev(dev); > + > + /* No calls of netif_napi_del() needed as free_candev() will do this */ > + > + virtio_can_del_vq(vdev); > + > + virtio_can_free_candev(dev); > +} > + > +static int virtio_can_validate(struct virtio_device *vdev) > +{ > + /* CAN needs always access to the config space. > + * Check that the driver can access the config space > + */ > + if (!vdev->config->get) { > + dev_err(&vdev->dev, "%s failure: config access disabled\n", > + __func__); > + return -EINVAL; > + } > + > + if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) { > + dev_err(&vdev->dev, > + "device does not comply with spec version 1.x\n"); > + return -EINVAL; > + } > + > + return 0; > +} > + > +static int virtio_can_probe(struct virtio_device *vdev) > +{ > + struct virtio_can_priv *priv; > + struct net_device *dev; > + int err; > + > + dev = alloc_candev(sizeof(struct virtio_can_priv), > + VIRTIO_CAN_ECHO_SKB_MAX); > + if (!dev) > + return -ENOMEM; > + > + priv = netdev_priv(dev); > + > + ida_init(&priv->tx_putidx_ida); > + > + netif_napi_add(dev, &priv->napi, virtio_can_rx_poll); > + netif_napi_add(dev, &priv->napi_tx, virtio_can_tx_poll); > + > + SET_NETDEV_DEV(dev, &vdev->dev); > + > + priv->dev = dev; > + priv->vdev = vdev; > + vdev->priv = priv; > + > + priv->can.do_set_mode = virtio_can_set_mode; > + /* Set Virtio CAN supported operations */ > + priv->can.ctrlmode_supported = CAN_CTRLMODE_BERR_REPORTING; > + if (virtio_has_feature(vdev, VIRTIO_CAN_F_CAN_FD)) { > + err = can_set_static_ctrlmode(dev, CAN_CTRLMODE_FD); > + if (err != 0) > + goto on_failure; > + } > + > + /* Initialize virtqueues */ > + err = virtio_can_find_vqs(priv); > + if (err != 0) > + goto on_failure; > + > + spin_lock_init(&priv->tx_lock); > + mutex_init(&priv->ctrl_lock); > + > + init_completion(&priv->ctrl_done); > + > + if (virtio_has_feature(vdev, VIRTIO_CAN_F_CAN_FD)) > + priv->sdu_len = CANFD_MAX_DLEN; > + else > + priv->sdu_len = CAN_MAX_DLEN; Consider replacing sdu_len with something like rpkt_len, which is directly related to priv->rpkt and can make code more readable, here and in other locations. E.g.: priv->rpkt_len = sizeof(struct virtio_can_rx); if (virtio_has_feature(vdev, VIRTIO_CAN_F_CAN_FD)) priv->rpkt_len += CANFD_MAX_DLEN; else priv->rpkt_len += CAN_MAX_DLEN; priv->rpkt = kzalloc(priv->rpkt_len * ... > + > + priv->rpkt = kzalloc((sizeof(struct virtio_can_rx) + priv->sdu_len) * > + > priv->vqs[VIRTIO_CAN_QUEUE_RX]->num_free, > + GFP_KERNEL); If I'm not mistaken, priv->rpkt is never freed. Consider moving to devm_kzalloc(). > + if (!priv->rpkt) { > + virtio_can_del_vq(vdev); > + goto on_failure; > + } > + virtio_can_populate_rx_vq(vdev); > + > + err = register_virtio_can_dev(dev); > + if (err) { > + virtio_can_del_vq(vdev); > + goto on_failure; > + } > + > + napi_enable(&priv->napi); > + napi_enable(&priv->napi_tx); Most of the existing drivers enable the napi(s) during the open() phase, IIUC to avoid scheduling napi operations for devices that might never get used. But here maybe there is a specific reason to do it this way? > + > + return 0; > + > +on_failure: > + virtio_can_free_candev(dev); > + return err; > +} > + > +/* Compare with m_can.c/m_can_suspend(), virtio_net.c/virtnet_freeze() and > + * virtio_card.c/virtsnd_freeze() > + */ > +static int __maybe_unused virtio_can_freeze(struct virtio_device *vdev) > +{ > + struct virtio_can_priv *priv = vdev->priv; > + struct net_device *ndev = priv->dev; > + > + napi_disable(&priv->napi); > + napi_disable(&priv->napi_tx); > + > + if (netif_running(ndev)) { > + netif_stop_queue(ndev); > + netif_device_detach(ndev); > + virtio_can_stop(ndev); > + } > + > + priv->can.state = CAN_STATE_SLEEPING; > + > + virtio_can_del_vq(vdev); > + > + return 0; > +} > + > +/* Compare with m_can.c/m_can_resume(), virtio_net.c/virtnet_restore() and > + * virtio_card.c/virtsnd_restore() > + */ > +static int __maybe_unused virtio_can_restore(struct virtio_device *vdev) > +{ > + struct virtio_can_priv *priv = vdev->priv; > + struct net_device *ndev = priv->dev; > + int err; > + > + err = virtio_can_find_vqs(priv); > + if (err != 0) > + return err; > + virtio_can_populate_rx_vq(vdev); > + > + priv->can.state = CAN_STATE_ERROR_ACTIVE; > + > + if (netif_running(ndev)) { > + virtio_can_start(ndev); > + netif_device_attach(ndev); > + netif_start_queue(ndev); > + } > + > + napi_enable(&priv->napi); > + napi_enable(&priv->napi_tx); > + > + return 0; > +} > + > +static struct virtio_device_id virtio_can_id_table[] = { > + { VIRTIO_ID_CAN, VIRTIO_DEV_ANY_ID }, > + { 0 }, > +}; > + > +static unsigned int features[] = { > + VIRTIO_CAN_F_CAN_CLASSIC, > + VIRTIO_CAN_F_CAN_FD, > + VIRTIO_CAN_F_LATE_TX_ACK, > + VIRTIO_CAN_F_RTR_FRAMES, > +}; > + > +static struct virtio_driver virtio_can_driver = { > + .feature_table = features, > + .feature_table_size = ARRAY_SIZE(features), > + .driver.name = KBUILD_MODNAME, > + .driver.owner = THIS_MODULE, > + .id_table = virtio_can_id_table, > + .validate = virtio_can_validate, > + .probe = virtio_can_probe, > + .remove = virtio_can_remove, > + .config_changed = virtio_can_config_changed, > +#ifdef CONFIG_PM_SLEEP > + .freeze = virtio_can_freeze, > + .restore = virtio_can_restore, > +#endif > +}; > + > +module_virtio_driver(virtio_can_driver); > +MODULE_DEVICE_TABLE(virtio, virtio_can_id_table); > + > +MODULE_AUTHOR("OpenSynergy GmbH"); > +MODULE_LICENSE("GPL"); > +MODULE_DESCRIPTION("CAN bus driver for Virtio CAN controller"); > diff --git a/include/uapi/linux/virtio_can.h b/include/uapi/linux/virtio_can.h > new file mode 100644 > index 000000000000..ade068188d22 > --- /dev/null > +++ b/include/uapi/linux/virtio_can.h > @@ -0,0 +1,78 @@ > +/* SPDX-License-Identifier: BSD-3-Clause */ > +/* > + * Copyright (C) 2021-2023 OpenSynergy GmbH > + * Copyright Red Hat, Inc. 2025 > + */ > +#ifndef _LINUX_VIRTIO_VIRTIO_CAN_H > +#define _LINUX_VIRTIO_VIRTIO_CAN_H > + > +#include <linux/types.h> > +#include <linux/virtio_types.h> > +#include <linux/virtio_ids.h> > +#include <linux/virtio_config.h> > + > +/* Feature bit numbers */ > +#define VIRTIO_CAN_F_CAN_CLASSIC 0 > +#define VIRTIO_CAN_F_CAN_FD 1 > +#define VIRTIO_CAN_F_RTR_FRAMES 2 > +#define VIRTIO_CAN_F_LATE_TX_ACK 3 > + > +/* CAN Result Types */ > +#define VIRTIO_CAN_RESULT_OK 0 > +#define VIRTIO_CAN_RESULT_NOT_OK 1 > + > +/* CAN flags to determine type of CAN Id */ > +#define VIRTIO_CAN_FLAGS_EXTENDED 0x8000 > +#define VIRTIO_CAN_FLAGS_FD 0x4000 > +#define VIRTIO_CAN_FLAGS_RTR 0x2000 > + > +#define VIRTIO_CAN_MAX_DLEN 64 // this is like CANFD_MAX_DLEN > + > +struct virtio_can_config { > +#define VIRTIO_CAN_S_CTRL_BUSOFF (1u << 0) /* Controller BusOff */ > + /* CAN controller status */ > + __le16 status; > +}; > + > +/* TX queue message types */ > +struct virtio_can_tx_out { > +#define VIRTIO_CAN_TX 0x0001 > + __le16 msg_type; > + __le16 length; /* 0..8 CC, 0..64 CAN-FD, 0..2048 CAN-XL, 12 bits */ > + __u8 reserved_classic_dlc; /* If CAN classic length = 8 then DLC can be > 8..15 */ > + __u8 padding; > + __le16 reserved_xl_priority; /* May be needed for CAN XL priority */ > + __le32 flags; > + __le32 can_id; > + __u8 sdu[] __counted_by(length); > +}; > + > +struct virtio_can_tx_in { > + __u8 result; > +}; > + > +/* RX queue message types */ > +struct virtio_can_rx { > +#define VIRTIO_CAN_RX 0x0101 > + __le16 msg_type; > + __le16 length; /* 0..8 CC, 0..64 CAN-FD, 0..2048 CAN-XL, 12 bits */ > + __u8 reserved_classic_dlc; /* If CAN classic length = 8 then DLC can be > 8..15 */ > + __u8 padding; > + __le16 reserved_xl_priority; /* May be needed for CAN XL priority */ > + __le32 flags; > + __le32 can_id; > + __u8 sdu[] __counted_by(length); > +}; > + > +/* Control queue message types */ > +struct virtio_can_control_out { > +#define VIRTIO_CAN_SET_CTRL_MODE_START 0x0201 > +#define VIRTIO_CAN_SET_CTRL_MODE_STOP 0x0202 > + __le16 msg_type; > +}; > + > +struct virtio_can_control_in { > + __u8 result; > +}; > + > +#endif /* #ifndef _LINUX_VIRTIO_VIRTIO_CAN_H */ > > base-commit: 0d97f2067c166eb495771fede9f7b73999c67f66 > -- > 2.42.0 Thank you again! Regards, Francesco
