[PATCH v5] can: virtio: Initial virtio CAN driver.

Mikhail Golubev-Ciuchea
2024-01-08T13:11:07Z

From: Harald Mommer <harald.mommer@opensynergy.com>

- CAN Control

- "ip link set up can0" starts the virtual CAN controller,
- "ip link set up can0" stops the virtual CAN controller

- CAN RX

Receive CAN frames. CAN frames can be standard or extended, classic or
CAN FD. Classic CAN RTR frames are supported.

- CAN TX

Send CAN frames. CAN frames can be standard or extended, classic or
CAN FD. Classic CAN RTR frames are supported.

- CAN BusOff indication

CAN BusOff is handled by a bit in the configuration space.

Signed-off-by: Harald Mommer <Harald.Mommer@opensynergy.com>
Signed-off-by: Mikhail Golubev-Ciuchea <Mikhail.Golubev-Ciuchea@opensynergy.com>
Co-developed-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Damir Shaikhutdinov <Damir.Shaikhutdinov@opensynergy.com>
---

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/20230424-footwear-daily-9339bd0ec428-mkl@pengutronix.de/
* 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
* Fix CAN_EFF_MASK comparison
* Remove MISRA style code (e.g. '! = 0u')
* Remove priorities leftovers
* Remove BUGONs
* Based on virtio can spec RFCv3
* Tested with https://github.com/OpenSynergy/qemu/tree/virtio-can-spec-rfc-v3

MAINTAINERS | 7 +
drivers/net/can/Kconfig | 12 +
drivers/net/can/Makefile | 1 +
drivers/net/can/virtio_can.c | 1008 +++++++++++++++++++++++++++++++
include/uapi/linux/virtio_can.h | 75 +++
5 files changed, 1103 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 cef9597b90ac..d3892370db2b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -23214,6 +23214,13 @@ 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" <harald.mommer@opensynergy.com>
+L: linux-can@vger.kernel.org
+S: Maintained
+F: drivers/net/can/virtio_can.c
+F: include/uapi/linux/virtio_can.h
+
VIRTIO CONSOLE DRIVER
M: Amit Shah <amit@kernel.org>
L: virtualization@lists.linux.dev
diff --git a/drivers/net/can/Kconfig b/drivers/net/can/Kconfig
index eb410714afc2..f966bab19ed8 100644
--- a/drivers/net/can/Kconfig
+++ b/drivers/net/can/Kconfig
@@ -215,6 +215,18 @@ 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 ff8f76295d13..4488e591736e 100644
--- a/drivers/net/can/Makefile
+++ b/drivers/net/can/Makefile
@@ -30,6 +30,7 @@ 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..924a7c19e438
--- /dev/null
+++ b/drivers/net/can/virtio_can.c
@@ -0,0 +1,1008 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * CAN bus driver for the Virtio CAN controller
+ * Copyright (C) 2021-2023 OpenSynergy GmbH
+ */
+
+#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 {
+ struct list_head list;
+ unsigned int putidx;
+ struct virtio_can_tx_out tx_out;
+ struct virtio_can_tx_in tx_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];
+ /* 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;
+ /* List of virtio CAN TX message */
+ struct list_head tx_list;
+ /* Array of receive queue messages */
+ struct virtio_can_rx rpkt[128];
+ /* Those control queue messages cannot live on the stack! */
+ struct virtio_can_control_out cpkt_out;
+ struct virtio_can_control_in cpkt_in;
+ /* Data to get and maintain the putidx for local TX echo */
+ struct ida tx_putidx_ida;
+ /* In flight TX messages */
+ atomic_t tx_inflight;
+ /* 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_add(1, &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_sub(1, &priv->tx_inflight);
+}
+
+/* Create a scatter-gather list representing our input buffer and put
+ * it in the queue.
+ *
+ * Callers should take appropriate locks.
+ */
+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;
+ 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().
+ */
+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);
+
+ priv->cpkt_out.msg_type = cpu_to_le16(msg_type);
+ sg_init_one(&sg_out, &priv->cpkt_out, sizeof(priv->cpkt_out));
+ sg_init_one(&sg_in, &priv->cpkt_in, sizeof(priv->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__);
+ }
+
+ if (!virtqueue_kick(vq)) {
+ /* Not expected to happen */
+ dev_err(dev, "%s(): Kick failed\n", __func__);
+ }
+
+ while (!virtqueue_get_buf(vq, &len) && !virtqueue_is_broken(vq))
+ wait_for_completion(&priv->ctrl_done);
+
+ mutex_unlock(&priv->ctrl_lock);
+
+ return priv->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.
+ */
+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), 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;
+
+ /* Protect list operation */
+ spin_lock_irqsave(&priv->tx_lock, flags);
+ list_add_tail(&can_tx_msg->list, &priv->tx_list);
+ spin_unlock_irqrestore(&priv->tx_lock, flags);
+
+ /* 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)) { /* checking vq->num_free in flow control */
+ list_del(&can_tx_msg->list);
+ 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);
+
+ 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) {
+ /* Here also frames with result != VIRTIO_CAN_RESULT_OK are
+ * echoed. Intentional to bring a waiting process in an upper
+ * layer to an end.
+ * TODO: Any better means to indicate a problem here?
+ */
+ if (result != VIRTIO_CAN_RESULT_OK)
+ netdev_warn(dev, "TX ACK: Result = %u\n", result);
+
+ stats->tx_bytes += can_get_echo_skb(dev, can_tx_msg->putidx,
+ NULL);
+ stats->tx_packets++;
+ } else {
+ netdev_dbg(dev, "TX ACK: Controller inactive, drop echo\n");
+ can_free_echo_skb(dev, can_tx_msg->putidx, NULL);
+ }
+
+ list_del(&can_tx_msg->list);
+ 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));
+
+ 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_vqs(struct virtio_device *vdev)
+
+{
+ struct virtio_can_priv *priv = vdev->priv;
+ struct virtqueue *vq;
+ unsigned int idx;
+ int ret;
+
+ /* Fill RX queue */
+ vq = priv->vqs[VIRTIO_CAN_QUEUE_RX];
+ for (idx = 0; idx < ARRAY_SIZE(priv->rpkt); idx++) {
+ ret = virtio_can_add_inbuf(vq, &priv->rpkt[idx],
+ sizeof(struct virtio_can_rx));
+ if (ret < 0) {
+ dev_dbg(&vdev->dev, "rpkt fill: ret=%d, idx=%u\n",
+ ret, idx);
+ break;
+ }
+ }
+ dev_dbg(&vdev->dev, "%u rpkt added\n", idx);
+}
+
+static int virtio_can_find_vqs(struct virtio_can_priv *priv)
+{
+ /* 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.
+ */
+ static const char * const io_names[VIRTIO_CAN_QUEUE_COUNT] = {
+ "can-tx",
+ "can-rx",
+ "can-state-ctrl"
+ };
+
+ 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;
+
+ /* Find the queues. */
+ return virtio_find_vqs(priv->vdev, VIRTIO_CAN_QUEUE_COUNT, priv->vqs,
+ priv->io_callbacks, io_names, 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 list_head *cursor, *next;
+ 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 */
+
+ /* Is keeping track of allocated elements by an own linked list
+ * really necessary or may this be optimized using only
+ * virtqueue_detach_unused_buf()?
+ */
+ list_for_each_safe(cursor, next, &priv->tx_list) {
+ struct virtio_can_tx *can_tx;
+
+ can_tx = list_entry(cursor, struct virtio_can_tx, list);
+ list_del(cursor);
+ kfree(can_tx);
+ }
+
+ 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;
+
+ INIT_LIST_HEAD(&priv->tx_list);
+
+ spin_lock_init(&priv->tx_lock);
+ mutex_init(&priv->ctrl_lock);
+
+ init_completion(&priv->ctrl_done);
+
+ virtio_can_populate_vqs(vdev);
+
+ register_virtio_can_dev(dev);
+
+ napi_enable(&priv->napi);
+ napi_enable(&priv->napi_tx);
+
+ /* Request device going live */
+ virtio_device_ready(vdev); /* Optionally done by virtio_dev_probe() */
+
+ 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_vqs(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..7cf613bb3f1a
--- /dev/null
+++ b/include/uapi/linux/virtio_can.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/*
+ * Copyright (C) 2021-2023 OpenSynergy GmbH
+ */
+#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_LATE_TX_ACK 2
+#define VIRTIO_CAN_F_RTR_FRAMES 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
+
+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[64];
+};
+
+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[64];
+};
+
+/* 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 */
--
2.43.0