[1/7] CAN bus simple messages transport implementation for QEMU

Commit Message

Pavel Pisa Jan. 6, 2018, 8:47 p.m. UTC

From: Pavel Pisa <[e-mail]>

The CanBusState state structure is created for each
emulated CAN channel. Individual clients/emulated
CAN interfaces or host interface connection registers
to the bus by CanBusClientState structure.

The CAN core is prepared to support connection to the
real host CAN bus network. The commit with such support
for Linux SocketCAN follows.

Implementation is as simple as possible, no migration,
messages prioritization and queuing considered for now.
But it is intended to be extended when need arises.

Development repository and more documentation at

https://gitlab.fel.cvut.cz/canbus/qemu-canbus

The work is based on Jin Yang GSoC 2013 work funded
by Google and mentored in frame of RTEMS project GSoC
slot donated to QEMU.

Rewritten for QEMU-2.0+ versions and architecture cleanup
by Pavel Pisa (Czech Technical University in Prague).

Signed-off-by: Pavel Pisa <[e-mail]>
---
 default-configs/pci.mak |   1 +
 hw/Makefile.objs        |   1 +
 hw/can/Makefile.objs    |   6 ++
 hw/can/can_core.c       | 129 +++++++++++++++++++++++++++++++++++++++++++
 hw/can/can_host_stub.c  |  36 ++++++++++++
 include/can/can_emu.h   | 143 ++++++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 316 insertions(+)
 create mode 100644 hw/can/Makefile.objs
 create mode 100644 hw/can/can_core.c
 create mode 100644 hw/can/can_host_stub.c
 create mode 100644 include/can/can_emu.h

Comments

KONRAD Frederic Jan. 12, 2018, 10:07 a.m. UTC | #1

Hi Pavel,

On 01/06/2018 09:47 PM, [e-mail] wrote:
> From: Pavel Pisa <[e-mail]>
> 
> The CanBusState state structure is created for each
> emulated CAN channel. Individual clients/emulated
> CAN interfaces or host interface connection registers
> to the bus by CanBusClientState structure.
> 
> The CAN core is prepared to support connection to the
> real host CAN bus network. The commit with such support
> for Linux SocketCAN follows.
> 
> Implementation is as simple as possible, no migration,
> messages prioritization and queuing considered for now.
> But it is intended to be extended when need arises.
> 
> Development repository and more documentation at
> 
> https://gitlab.fel.cvut.cz/canbus/qemu-canbus
> 
> The work is based on Jin Yang GSoC 2013 work funded
> by Google and mentored in frame of RTEMS project GSoC
> slot donated to QEMU.
> 
> Rewritten for QEMU-2.0+ versions and architecture cleanup
> by Pavel Pisa (Czech Technical University in Prague).
> 
> Signed-off-by: Pavel Pisa <[e-mail]>
> ---
>   default-configs/pci.mak |   1 +
>   hw/Makefile.objs        |   1 +
>   hw/can/Makefile.objs    |   6 ++
>   hw/can/can_core.c       | 129 +++++++++++++++++++++++++++++++++++++++++++
>   hw/can/can_host_stub.c  |  36 ++++++++++++
>   include/can/can_emu.h   | 143 ++++++++++++++++++++++++++++++++++++++++++++++++
>   6 files changed, 316 insertions(+)
>   create mode 100644 hw/can/Makefile.objs
>   create mode 100644 hw/can/can_core.c
>   create mode 100644 hw/can/can_host_stub.c
>   create mode 100644 include/can/can_emu.h
> 
> diff --git a/default-configs/pci.mak b/default-configs/pci.mak
> index e514bdef42..bbe11887a1 100644
> --- a/default-configs/pci.mak
> +++ b/default-configs/pci.mak
> @@ -31,6 +31,7 @@ CONFIG_ESP_PCI=y
>   CONFIG_SERIAL=y
>   CONFIG_SERIAL_ISA=y
>   CONFIG_SERIAL_PCI=y
> +CONFIG_CAN_CORE=y
>   CONFIG_IPACK=y
>   CONFIG_WDT_IB6300ESB=y
>   CONFIG_PCI_TESTDEV=y
> diff --git a/hw/Makefile.objs b/hw/Makefile.objs
> index cf4cb2010b..9d84b8faaa 100644
> --- a/hw/Makefile.objs
> +++ b/hw/Makefile.objs
> @@ -6,6 +6,7 @@ devices-dirs-$(CONFIG_SOFTMMU) += block/
>   devices-dirs-$(CONFIG_SOFTMMU) += bt/
>   devices-dirs-$(CONFIG_SOFTMMU) += char/
>   devices-dirs-$(CONFIG_SOFTMMU) += cpu/
> +devices-dirs-$(CONFIG_SOFTMMU) += can/
>   devices-dirs-$(CONFIG_SOFTMMU) += display/
>   devices-dirs-$(CONFIG_SOFTMMU) += dma/
>   devices-dirs-$(CONFIG_SOFTMMU) += gpio/
> diff --git a/hw/can/Makefile.objs b/hw/can/Makefile.objs
> new file mode 100644
> index 0000000000..1028d7c455
> --- /dev/null
> +++ b/hw/can/Makefile.objs
> @@ -0,0 +1,6 @@
> +# CAN bus interfaces emulation and infrastructure
> +
> +ifeq ($(CONFIG_CAN_CORE),y)
> +common-obj-y += can_core.o
> +common-obj-y += can_host_stub.o
> +endif
> diff --git a/hw/can/can_core.c b/hw/can/can_core.c
> new file mode 100644
> index 0000000000..49ba3c6ef2
> --- /dev/null
> +++ b/hw/can/can_core.c
> @@ -0,0 +1,129 @@
> +/*
> + * CAN common CAN bus emulation support
> + *
> + * Copyright (c) 2013-2014 Jin Yang
> + * Copyright (c) 2014-2018 Pavel Pisa
> + *
> + * Initial development supported by Google GSoC 2013 from RTEMS project slot
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to deal
> + * in the Software without restriction, including without limitation the rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +#include "qemu/osdep.h"
> +#include "chardev/char.h"
> +#include "qemu/sockets.h"
> +#include "qemu/error-report.h"
> +#include "hw/hw.h"
> +#include "can/can_emu.h"
> +
> +#ifndef DEBUG_CAN
> +#define DEBUG_CAN 0
> +#endif /*DEBUG_CAN*/

This seems not used?

> +
> +static QTAILQ_HEAD(, CanBusState) can_buses =
> +    QTAILQ_HEAD_INITIALIZER(can_buses);
> +
> +CanBusState *can_bus_find_by_name(const char *name, bool create_missing)
> +{
> +    CanBusState *bus;
> +
> +    if (name == NULL) {
> +        name = "canbus0";
> +    }
> +
> +    QTAILQ_FOREACH(bus, &can_buses, next) {
> +        if (!strcmp(bus->name, name)) {
> +            return bus;
> +        }
> +    }
> +
> +    if (!create_missing) {
> +        return 0;
> +    }
> +
> +    bus = g_malloc0(sizeof(*bus));
> +    if (bus == NULL) {
> +        return NULL;
> +    }
> +
> +    QTAILQ_INIT(&bus->clients);
> +
> +    bus->name = g_strdup(name);
> +
> +    QTAILQ_INSERT_TAIL(&can_buses, bus, next);
> +    return bus;
> +}
> +
> +int can_bus_insert_client(CanBusState *bus, CanBusClientState *client)
> +{
> +    client->bus = bus;
> +    QTAILQ_INSERT_TAIL(&bus->clients, client, next);
> +    return 0;
> +}
> +
> +int can_bus_remove_client(CanBusClientState *client)
> +{
> +    CanBusState *bus = client->bus;
> +    if (bus == NULL) {
> +        return 0;
> +    }
> +
> +    QTAILQ_REMOVE(&bus->clients, client, next);
> +    client->bus = NULL;
> +    return 1;
> +}
> +
> +ssize_t can_bus_client_send(CanBusClientState *client,
> +             const struct qemu_can_frame *frames, size_t frames_cnt)
> +{
> +    int ret = 0;
> +    CanBusState *bus = client->bus;
> +    CanBusClientState *peer;
> +    if (bus == NULL) {
> +        return -1;
> +    }
> +
> +    QTAILQ_FOREACH(peer, &bus->clients, next) {
> +        if (peer->info->can_receive(peer)) {
> +            if (peer == client) {
> +                /* No loopback support for now */
> +                continue;
> +            }
> +            if (peer->info->receive(peer, frames, frames_cnt) > 0) {
> +                ret = 1;
> +            }
> +        }
> +    }
> +
> +    return ret;
> +}
> +
> +int can_bus_client_set_filters(CanBusClientState *client,
> +             const struct qemu_can_filter *filters, size_t filters_cnt)
> +{
> +    return 0;
> +}
> +
> +int can_bus_connect_to_host_device(CanBusState *bus, const char *name)
> +{
> +    if (can_bus_connect_to_host_variant == NULL) {
> +        error_report("CAN bus connect to host device not supported on this system");
> +        exit(1);
> +    }
> +    return can_bus_connect_to_host_variant(bus, name);
> +}
> diff --git a/hw/can/can_host_stub.c b/hw/can/can_host_stub.c
> new file mode 100644
> index 0000000000..748d25f995
> --- /dev/null
> +++ b/hw/can/can_host_stub.c
> @@ -0,0 +1,36 @@
> +/*
> + * CAN stub to connect to host system CAN interface
> + *
> + * Copyright (c) 2013-2014 Jin Yang
> + * Copyright (c) 2014-2018 Pavel Pisa
> + *
> + * Initial development supported by Google GSoC 2013 from RTEMS project slot
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to deal
> + * in the Software without restriction, including without limitation the rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +#include "qemu/osdep.h"
> +#include "chardev/char.h"
> +#include "qemu/sockets.h"
> +#include "qemu/error-report.h"
> +#include "hw/hw.h"
> +#include "can/can_emu.h"
> +
> +
> +int (*can_bus_connect_to_host_variant)(CanBusState *bus, const char *name) =
> +        NULL;
> diff --git a/include/can/can_emu.h b/include/can/can_emu.h
> new file mode 100644
> index 0000000000..5c149a2ae9
> --- /dev/null
> +++ b/include/can/can_emu.h
> @@ -0,0 +1,143 @@
> +/*
> + * CAN common CAN bus emulation support
> + *
> + * Copyright (c) 2013-2014 Jin Yang
> + * Copyright (c) 2014-2018 Pavel Pisa
> + *
> + * Initial development supported by Google GSoC 2013 from RTEMS project slot
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to deal
> + * in the Software without restriction, including without limitation the rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +
> +#ifndef NET_CAN_EMU_H
> +#define NET_CAN_EMU_H
> +
> +#include "qemu/queue.h"
> +
> +/* NOTE: the following two structures is copied from <linux/can.h>. */
> +
> +/*
> + * Controller Area Network Identifier structure
> + *
> + * bit 0-28    : CAN identifier (11/29 bit)
> + * bit 29      : error frame flag (0 = data frame, 1 = error frame)
> + * bit 30      : remote transmission request flag (1 = rtr frame)
> + * bit 31      : frame format flag (0 = standard 11 bit, 1 = extended 29 bit)
> + */
> +typedef uint32_t qemu_canid_t;
> +
> +typedef struct qemu_can_frame {
> +    qemu_canid_t    can_id;  /* 32 bit CAN_ID + EFF/RTR/ERR flags */
> +    uint8_t         can_dlc; /* data length code: 0 .. 8 */
> +    uint8_t         data[8] QEMU_ALIGNED(8);
> +} qemu_can_frame;
> +
> +/* Keep defines for QEMU separate from Linux ones for now */
> +
> +#define QEMU_CAN_EFF_FLAG 0x80000000U /* EFF/SFF is set in the MSB */
> +#define QEMU_CAN_RTR_FLAG 0x40000000U /* remote transmission request */
> +#define QEMU_CAN_ERR_FLAG 0x20000000U /* error message frame */
> +
> +#define QEMU_CAN_SFF_MASK 0x000007FFU /* standard frame format (SFF) */
> +#define QEMU_CAN_EFF_MASK 0x1FFFFFFFU /* extended frame format (EFF) */
> +
> +/**
> + * struct qemu_can_filter - CAN ID based filter in can_register().
> + * @can_id:   relevant bits of CAN ID which are not masked out.
> + * @can_mask: CAN mask (see description)
> + *
> + * Description:
> + * A filter matches, when
> + *
> + *          <received_can_id> & mask == can_id & mask
> + *
> + * The filter can be inverted (QEMU_CAN_INV_FILTER bit set in can_id) or it can
> + * filter for error message frames (QEMU_CAN_ERR_FLAG bit set in mask).
> + */
> +typedef struct qemu_can_filter {
> +    qemu_canid_t    can_id;
> +    qemu_canid_t    can_mask;
> +} qemu_can_filter;
> +
> +#define QEMU_CAN_INV_FILTER 0x20000000U /* to be set in qemu_can_filter.can_id */
> +
> +typedef struct CanBusClientState CanBusClientState;
> +typedef struct CanBusState CanBusState;
> +
> +typedef struct CanBusClientInfo {
> +    /*CanBusClientOptionsKind type;*/

You can drop it.

> +    size_t size;
> +    int (*can_receive)(CanBusClientState *);
> +    ssize_t (*receive)(CanBusClientState *,
> +        const struct qemu_can_frame *frames, size_t frames_cnt);
> +    void (*cleanup) (CanBusClientState *);
> +    void (*poll)(CanBusClientState *, bool enable);
> +} CanBusClientInfo;
> +
> +struct CanBusClientState {
> +    CanBusClientInfo *info;
> +    CanBusState *bus;
> +    int link_down;
> +    QTAILQ_ENTRY(CanBusClientState) next;
> +    CanBusClientState *peer;
> +    /*CanBusQueue *incoming_queue;*/
> +    char *model;
> +    char *name;
> +    /*unsigned receive_disabled : 1;*/
> +    void (*destructor)(CanBusClientState *);
> +    /*unsigned int queue_index;*/
> +    /*unsigned rxfilter_notify_enabled:1;*/

Same here.

> +};
> +
> +struct CanBusState {
> +    char *name;
> +    QTAILQ_HEAD(, CanBusClientState) clients;
> +    QTAILQ_ENTRY(CanBusState) next;
> +};
> +
> +extern int (*can_bus_connect_to_host_variant)(CanBusState *bus, const char *name);
> +
> +static inline
> +int can_bus_filter_match(struct qemu_can_filter *filter, qemu_canid_t can_id)
> +{
> +    int m;
> +    if (((can_id | filter->can_mask) & QEMU_CAN_ERR_FLAG)) {
> +        return (filter->can_mask & QEMU_CAN_ERR_FLAG) != 0;
> +    }
> +    m = (can_id & filter->can_mask) == (filter->can_id & filter->can_mask);
> +    return filter->can_id & QEMU_CAN_INV_FILTER ? !m : m;
> +}

Is it really required to inline this?

Fred

> +
> +CanBusState *can_bus_find_by_name(const char *name, bool create_missing);
> +
> +int can_bus_insert_client(CanBusState *bus, CanBusClientState *client);
> +
> +int can_bus_remove_client(CanBusClientState *client);
> +
> +ssize_t can_bus_client_send(CanBusClientState *,
> +                            const struct qemu_can_frame *frames,
> +                            size_t frames_cnt);
> +
> +int can_bus_client_set_filters(CanBusClientState *,
> +                               const struct qemu_can_filter *filters,
> +                               size_t filters_cnt);
> +
> +int can_bus_connect_to_host_device(CanBusState *bus, const char *host_dev_name);
> +
> +#endif
>

Patch

diff --git a/default-configs/pci.mak b/default-configs/pci.mak
index e514bdef42..bbe11887a1 100644
--- a/default-configs/pci.mak
+++ b/default-configs/pci.mak
@@ -31,6 +31,7 @@  CONFIG_ESP_PCI=y
 CONFIG_SERIAL=y
 CONFIG_SERIAL_ISA=y
 CONFIG_SERIAL_PCI=y
+CONFIG_CAN_CORE=y
 CONFIG_IPACK=y
 CONFIG_WDT_IB6300ESB=y
 CONFIG_PCI_TESTDEV=y
diff --git a/hw/Makefile.objs b/hw/Makefile.objs
index cf4cb2010b..9d84b8faaa 100644
--- a/hw/Makefile.objs
+++ b/hw/Makefile.objs
@@ -6,6 +6,7 @@  devices-dirs-$(CONFIG_SOFTMMU) += block/
 devices-dirs-$(CONFIG_SOFTMMU) += bt/
 devices-dirs-$(CONFIG_SOFTMMU) += char/
 devices-dirs-$(CONFIG_SOFTMMU) += cpu/
+devices-dirs-$(CONFIG_SOFTMMU) += can/
 devices-dirs-$(CONFIG_SOFTMMU) += display/
 devices-dirs-$(CONFIG_SOFTMMU) += dma/
 devices-dirs-$(CONFIG_SOFTMMU) += gpio/
diff --git a/hw/can/Makefile.objs b/hw/can/Makefile.objs
new file mode 100644
index 0000000000..1028d7c455
--- /dev/null
+++ b/hw/can/Makefile.objs
@@ -0,0 +1,6 @@ 
+# CAN bus interfaces emulation and infrastructure
+
+ifeq ($(CONFIG_CAN_CORE),y)
+common-obj-y += can_core.o
+common-obj-y += can_host_stub.o
+endif
diff --git a/hw/can/can_core.c b/hw/can/can_core.c
new file mode 100644
index 0000000000..49ba3c6ef2
--- /dev/null
+++ b/hw/can/can_core.c
@@ -0,0 +1,129 @@ 
+/*
+ * CAN common CAN bus emulation support
+ *
+ * Copyright (c) 2013-2014 Jin Yang
+ * Copyright (c) 2014-2018 Pavel Pisa
+ *
+ * Initial development supported by Google GSoC 2013 from RTEMS project slot
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include "qemu/osdep.h"
+#include "chardev/char.h"
+#include "qemu/sockets.h"
+#include "qemu/error-report.h"
+#include "hw/hw.h"
+#include "can/can_emu.h"
+
+#ifndef DEBUG_CAN
+#define DEBUG_CAN 0
+#endif /*DEBUG_CAN*/
+
+static QTAILQ_HEAD(, CanBusState) can_buses =
+    QTAILQ_HEAD_INITIALIZER(can_buses);
+
+CanBusState *can_bus_find_by_name(const char *name, bool create_missing)
+{
+    CanBusState *bus;
+
+    if (name == NULL) {
+        name = "canbus0";
+    }
+
+    QTAILQ_FOREACH(bus, &can_buses, next) {
+        if (!strcmp(bus->name, name)) {
+            return bus;
+        }
+    }
+
+    if (!create_missing) {
+        return 0;
+    }
+
+    bus = g_malloc0(sizeof(*bus));
+    if (bus == NULL) {
+        return NULL;
+    }
+
+    QTAILQ_INIT(&bus->clients);
+
+    bus->name = g_strdup(name);
+
+    QTAILQ_INSERT_TAIL(&can_buses, bus, next);
+    return bus;
+}
+
+int can_bus_insert_client(CanBusState *bus, CanBusClientState *client)
+{
+    client->bus = bus;
+    QTAILQ_INSERT_TAIL(&bus->clients, client, next);
+    return 0;
+}
+
+int can_bus_remove_client(CanBusClientState *client)
+{
+    CanBusState *bus = client->bus;
+    if (bus == NULL) {
+        return 0;
+    }
+
+    QTAILQ_REMOVE(&bus->clients, client, next);
+    client->bus = NULL;
+    return 1;
+}
+
+ssize_t can_bus_client_send(CanBusClientState *client,
+             const struct qemu_can_frame *frames, size_t frames_cnt)
+{
+    int ret = 0;
+    CanBusState *bus = client->bus;
+    CanBusClientState *peer;
+    if (bus == NULL) {
+        return -1;
+    }
+
+    QTAILQ_FOREACH(peer, &bus->clients, next) {
+        if (peer->info->can_receive(peer)) {
+            if (peer == client) {
+                /* No loopback support for now */
+                continue;
+            }
+            if (peer->info->receive(peer, frames, frames_cnt) > 0) {
+                ret = 1;
+            }
+        }
+    }
+
+    return ret;
+}
+
+int can_bus_client_set_filters(CanBusClientState *client,
+             const struct qemu_can_filter *filters, size_t filters_cnt)
+{
+    return 0;
+}
+
+int can_bus_connect_to_host_device(CanBusState *bus, const char *name)
+{
+    if (can_bus_connect_to_host_variant == NULL) {
+        error_report("CAN bus connect to host device not supported on this system");
+        exit(1);
+    }
+    return can_bus_connect_to_host_variant(bus, name);
+}
diff --git a/hw/can/can_host_stub.c b/hw/can/can_host_stub.c
new file mode 100644
index 0000000000..748d25f995
--- /dev/null
+++ b/hw/can/can_host_stub.c
@@ -0,0 +1,36 @@ 
+/*
+ * CAN stub to connect to host system CAN interface
+ *
+ * Copyright (c) 2013-2014 Jin Yang
+ * Copyright (c) 2014-2018 Pavel Pisa
+ *
+ * Initial development supported by Google GSoC 2013 from RTEMS project slot
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include "qemu/osdep.h"
+#include "chardev/char.h"
+#include "qemu/sockets.h"
+#include "qemu/error-report.h"
+#include "hw/hw.h"
+#include "can/can_emu.h"
+
+
+int (*can_bus_connect_to_host_variant)(CanBusState *bus, const char *name) =
+        NULL;
diff --git a/include/can/can_emu.h b/include/can/can_emu.h
new file mode 100644
index 0000000000..5c149a2ae9
--- /dev/null
+++ b/include/can/can_emu.h
@@ -0,0 +1,143 @@ 
+/*
+ * CAN common CAN bus emulation support
+ *
+ * Copyright (c) 2013-2014 Jin Yang
+ * Copyright (c) 2014-2018 Pavel Pisa
+ *
+ * Initial development supported by Google GSoC 2013 from RTEMS project slot
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef NET_CAN_EMU_H
+#define NET_CAN_EMU_H
+
+#include "qemu/queue.h"
+
+/* NOTE: the following two structures is copied from <linux/can.h>. */
+
+/*
+ * Controller Area Network Identifier structure
+ *
+ * bit 0-28    : CAN identifier (11/29 bit)
+ * bit 29      : error frame flag (0 = data frame, 1 = error frame)
+ * bit 30      : remote transmission request flag (1 = rtr frame)
+ * bit 31      : frame format flag (0 = standard 11 bit, 1 = extended 29 bit)
+ */
+typedef uint32_t qemu_canid_t;
+
+typedef struct qemu_can_frame {
+    qemu_canid_t    can_id;  /* 32 bit CAN_ID + EFF/RTR/ERR flags */
+    uint8_t         can_dlc; /* data length code: 0 .. 8 */
+    uint8_t         data[8] QEMU_ALIGNED(8);
+} qemu_can_frame;
+
+/* Keep defines for QEMU separate from Linux ones for now */
+
+#define QEMU_CAN_EFF_FLAG 0x80000000U /* EFF/SFF is set in the MSB */
+#define QEMU_CAN_RTR_FLAG 0x40000000U /* remote transmission request */
+#define QEMU_CAN_ERR_FLAG 0x20000000U /* error message frame */
+
+#define QEMU_CAN_SFF_MASK 0x000007FFU /* standard frame format (SFF) */
+#define QEMU_CAN_EFF_MASK 0x1FFFFFFFU /* extended frame format (EFF) */
+
+/**
+ * struct qemu_can_filter - CAN ID based filter in can_register().
+ * @can_id:   relevant bits of CAN ID which are not masked out.
+ * @can_mask: CAN mask (see description)
+ *
+ * Description:
+ * A filter matches, when
+ *
+ *          <received_can_id> & mask == can_id & mask
+ *
+ * The filter can be inverted (QEMU_CAN_INV_FILTER bit set in can_id) or it can
+ * filter for error message frames (QEMU_CAN_ERR_FLAG bit set in mask).
+ */
+typedef struct qemu_can_filter {
+    qemu_canid_t    can_id;
+    qemu_canid_t    can_mask;
+} qemu_can_filter;
+
+#define QEMU_CAN_INV_FILTER 0x20000000U /* to be set in qemu_can_filter.can_id */
+
+typedef struct CanBusClientState CanBusClientState;
+typedef struct CanBusState CanBusState;
+
+typedef struct CanBusClientInfo {
+    /*CanBusClientOptionsKind type;*/
+    size_t size;
+    int (*can_receive)(CanBusClientState *);
+    ssize_t (*receive)(CanBusClientState *,
+        const struct qemu_can_frame *frames, size_t frames_cnt);
+    void (*cleanup) (CanBusClientState *);
+    void (*poll)(CanBusClientState *, bool enable);
+} CanBusClientInfo;
+
+struct CanBusClientState {
+    CanBusClientInfo *info;
+    CanBusState *bus;
+    int link_down;
+    QTAILQ_ENTRY(CanBusClientState) next;
+    CanBusClientState *peer;
+    /*CanBusQueue *incoming_queue;*/
+    char *model;
+    char *name;
+    /*unsigned receive_disabled : 1;*/
+    void (*destructor)(CanBusClientState *);
+    /*unsigned int queue_index;*/
+    /*unsigned rxfilter_notify_enabled:1;*/
+};
+
+struct CanBusState {
+    char *name;
+    QTAILQ_HEAD(, CanBusClientState) clients;
+    QTAILQ_ENTRY(CanBusState) next;
+};
+
+extern int (*can_bus_connect_to_host_variant)(CanBusState *bus, const char *name);
+
+static inline
+int can_bus_filter_match(struct qemu_can_filter *filter, qemu_canid_t can_id)
+{
+    int m;
+    if (((can_id | filter->can_mask) & QEMU_CAN_ERR_FLAG)) {
+        return (filter->can_mask & QEMU_CAN_ERR_FLAG) != 0;
+    }
+    m = (can_id & filter->can_mask) == (filter->can_id & filter->can_mask);
+    return filter->can_id & QEMU_CAN_INV_FILTER ? !m : m;
+}
+
+CanBusState *can_bus_find_by_name(const char *name, bool create_missing);
+
+int can_bus_insert_client(CanBusState *bus, CanBusClientState *client);
+
+int can_bus_remove_client(CanBusClientState *client);
+
+ssize_t can_bus_client_send(CanBusClientState *,
+                            const struct qemu_can_frame *frames,
+                            size_t frames_cnt);
+
+int can_bus_client_set_filters(CanBusClientState *,
+                               const struct qemu_can_filter *filters,
+                               size_t filters_cnt);
+
+int can_bus_connect_to_host_device(CanBusState *bus, const char *host_dev_name);
+
+#endif