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Date: Tue, 28 Jun 2022 18:31:29 +0200
From: Dario Binacchi <dario.binacchi@...rulasolutions.com>
To: linux-kernel@...r.kernel.org
Cc: michael@...rulasolutions.com,
Amarula patchwork <linux-amarula@...rulasolutions.com>,
Oliver Hartkopp <socketcan@...tkopp.net>,
Dario Binacchi <dario.binacchi@...rulasolutions.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Marc Kleine-Budde <mkl@...gutronix.de>,
Paolo Abeni <pabeni@...hat.com>,
Wolfgang Grandegger <wg@...ndegger.com>,
linux-can@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH v5 05/12] can: slcan: use CAN network device driver API
As suggested by commit [1], now the driver uses the functions and the
data structures provided by the CAN network device driver interface.
Currently the driver doesn't implement a way to set bitrate for SLCAN
based devices via ip tool, so you'll have to do this by slcand or
slcan_attach invocation through the -sX parameter:
- slcan_attach -f -s6 -o /dev/ttyACM0
- slcand -f -s8 -o /dev/ttyUSB0
where -s6 in will set adapter's bitrate to 500 Kbit/s and -s8 to
1Mbit/s.
See the table below for further CAN bitrates:
- s0 -> 10 Kbit/s
- s1 -> 20 Kbit/s
- s2 -> 50 Kbit/s
- s3 -> 100 Kbit/s
- s4 -> 125 Kbit/s
- s5 -> 250 Kbit/s
- s6 -> 500 Kbit/s
- s7 -> 800 Kbit/s
- s8 -> 1000 Kbit/s
In doing so, the struct can_priv::bittiming.bitrate of the driver is not
set and since the open_candev() checks that the bitrate has been set, it
must be a non-zero value, the bitrate is set to a fake value (-1U)
before it is called.
Using the rtnl_lock()/rtnl_unlock() functions has become a bit more
tricky as the register_candev() function indirectly calls rtnl_lock()
via register_netdev(). To avoid a deadlock it is therefore necessary to
call rtnl_unlock() before calling register_candev(). The same goes for
the unregister_candev() function.
[1] commit 39549eef3587f ("can: CAN Network device driver and Netlink interface")
Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
---
Changes in v5:
- Update the commit message.
- Restore the use of rtnl_lock() and rtnl_unlock().
Changes in v4:
- Update the commit description.
- Use the CAN_BITRATE_UNKNOWN macro.
- Use kfree_skb() instead of can_put_echo_skb() in the slc_xmit().
- Remove the `if (slcan_devs)' check in the slc_dealloc().
Changes in v3:
- Replace (-1) with (-1U) in the commit description.
Changes in v2:
- Move CAN_SLCAN Kconfig option inside CAN_DEV scope.
- Improve the commit message.
drivers/net/can/Kconfig | 40 ++++++++++----------
drivers/net/can/slcan.c | 82 ++++++++++++++++++++---------------------
2 files changed, 60 insertions(+), 62 deletions(-)
diff --git a/drivers/net/can/Kconfig b/drivers/net/can/Kconfig
index b2dcc1e5a388..45997d39621c 100644
--- a/drivers/net/can/Kconfig
+++ b/drivers/net/can/Kconfig
@@ -28,26 +28,6 @@ config CAN_VXCAN
This driver can also be built as a module. If so, the module
will be called vxcan.
-config CAN_SLCAN
- tristate "Serial / USB serial CAN Adaptors (slcan)"
- depends on TTY
- help
- CAN driver for several 'low cost' CAN interfaces that are attached
- via serial lines or via USB-to-serial adapters using the LAWICEL
- ASCII protocol. The driver implements the tty linediscipline N_SLCAN.
-
- As only the sending and receiving of CAN frames is implemented, this
- driver should work with the (serial/USB) CAN hardware from:
- www.canusb.com / www.can232.com / www.mictronics.de / www.canhack.de
-
- Userspace tools to attach the SLCAN line discipline (slcan_attach,
- slcand) can be found in the can-utils at the linux-can project, see
- https://github.com/linux-can/can-utils for details.
-
- The slcan driver supports up to 10 CAN netdevices by default which
- can be changed by the 'maxdev=xx' module option. This driver can
- also be built as a module. If so, the module will be called slcan.
-
config CAN_DEV
tristate "Platform CAN drivers with Netlink support"
default y
@@ -118,6 +98,26 @@ config CAN_KVASER_PCIEFD
Kvaser Mini PCI Express HS v2
Kvaser Mini PCI Express 2xHS v2
+config CAN_SLCAN
+ tristate "Serial / USB serial CAN Adaptors (slcan)"
+ depends on TTY
+ help
+ CAN driver for several 'low cost' CAN interfaces that are attached
+ via serial lines or via USB-to-serial adapters using the LAWICEL
+ ASCII protocol. The driver implements the tty linediscipline N_SLCAN.
+
+ As only the sending and receiving of CAN frames is implemented, this
+ driver should work with the (serial/USB) CAN hardware from:
+ www.canusb.com / www.can232.com / www.mictronics.de / www.canhack.de
+
+ Userspace tools to attach the SLCAN line discipline (slcan_attach,
+ slcand) can be found in the can-utils at the linux-can project, see
+ https://github.com/linux-can/can-utils for details.
+
+ The slcan driver supports up to 10 CAN netdevices by default which
+ can be changed by the 'maxdev=xx' module option. This driver can
+ also be built as a module. If so, the module will be called slcan.
+
config CAN_SUN4I
tristate "Allwinner A10 CAN controller"
depends on MACH_SUN4I || MACH_SUN7I || COMPILE_TEST
diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c
index c39580b142e0..bf84698f1a81 100644
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -56,7 +56,6 @@
#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/skb.h>
-#include <linux/can/can-ml.h>
MODULE_ALIAS_LDISC(N_SLCAN);
MODULE_DESCRIPTION("serial line CAN interface");
@@ -79,6 +78,7 @@ MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
#define SLC_EFF_ID_LEN 8
struct slcan {
+ struct can_priv can;
int magic;
/* Various fields. */
@@ -394,6 +394,8 @@ static int slc_close(struct net_device *dev)
clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
}
netif_stop_queue(dev);
+ close_candev(dev);
+ sl->can.state = CAN_STATE_STOPPED;
sl->rcount = 0;
sl->xleft = 0;
spin_unlock_bh(&sl->lock);
@@ -405,20 +407,34 @@ static int slc_close(struct net_device *dev)
static int slc_open(struct net_device *dev)
{
struct slcan *sl = netdev_priv(dev);
+ int err;
if (sl->tty == NULL)
return -ENODEV;
+ /* The baud rate is not set with the command
+ * `ip link set <iface> type can bitrate <baud>' and therefore
+ * can.bittiming.bitrate is CAN_BITRATE_UNSET (0), causing
+ * open_candev() to fail. So let's set to a fake value.
+ */
+ sl->can.bittiming.bitrate = CAN_BITRATE_UNKNOWN;
+ err = open_candev(dev);
+ if (err) {
+ netdev_err(dev, "failed to open can device\n");
+ return err;
+ }
+
+ sl->can.state = CAN_STATE_ERROR_ACTIVE;
sl->flags &= BIT(SLF_INUSE);
netif_start_queue(dev);
return 0;
}
-/* Hook the destructor so we can free slcan devs at the right point in time */
-static void slc_free_netdev(struct net_device *dev)
+static void slc_dealloc(struct slcan *sl)
{
- int i = dev->base_addr;
+ int i = sl->dev->base_addr;
+ free_candev(sl->dev);
slcan_devs[i] = NULL;
}
@@ -434,24 +450,6 @@ static const struct net_device_ops slc_netdev_ops = {
.ndo_change_mtu = slcan_change_mtu,
};
-static void slc_setup(struct net_device *dev)
-{
- dev->netdev_ops = &slc_netdev_ops;
- dev->needs_free_netdev = true;
- dev->priv_destructor = slc_free_netdev;
-
- dev->hard_header_len = 0;
- dev->addr_len = 0;
- dev->tx_queue_len = 10;
-
- dev->mtu = CAN_MTU;
- dev->type = ARPHRD_CAN;
-
- /* New-style flags. */
- dev->flags = IFF_NOARP;
- dev->features = NETIF_F_HW_CSUM;
-}
-
/******************************************
Routines looking at TTY side.
******************************************/
@@ -514,11 +512,8 @@ static void slc_sync(void)
static struct slcan *slc_alloc(void)
{
int i;
- char name[IFNAMSIZ];
struct net_device *dev = NULL;
- struct can_ml_priv *can_ml;
struct slcan *sl;
- int size;
for (i = 0; i < maxdev; i++) {
dev = slcan_devs[i];
@@ -531,16 +526,14 @@ static struct slcan *slc_alloc(void)
if (i >= maxdev)
return NULL;
- sprintf(name, "slcan%d", i);
- size = ALIGN(sizeof(*sl), NETDEV_ALIGN) + sizeof(struct can_ml_priv);
- dev = alloc_netdev(size, name, NET_NAME_UNKNOWN, slc_setup);
+ dev = alloc_candev(sizeof(*sl), 1);
if (!dev)
return NULL;
+ snprintf(dev->name, sizeof(dev->name), "slcan%d", i);
+ dev->netdev_ops = &slc_netdev_ops;
dev->base_addr = i;
sl = netdev_priv(dev);
- can_ml = (void *)sl + ALIGN(sizeof(*sl), NETDEV_ALIGN);
- can_set_ml_priv(dev, can_ml);
/* Initialize channel control data */
sl->magic = SLCAN_MAGIC;
@@ -605,26 +598,28 @@ static int slcan_open(struct tty_struct *tty)
set_bit(SLF_INUSE, &sl->flags);
- err = register_netdevice(sl->dev);
- if (err)
+ rtnl_unlock();
+ err = register_candev(sl->dev);
+ if (err) {
+ pr_err("slcan: can't register candev\n");
goto err_free_chan;
+ }
+ } else {
+ rtnl_unlock();
}
- /* Done. We have linked the TTY line to a channel. */
- rtnl_unlock();
tty->receive_room = 65536; /* We don't flow control */
/* TTY layer expects 0 on success */
return 0;
err_free_chan:
+ rtnl_lock();
sl->tty = NULL;
tty->disc_data = NULL;
clear_bit(SLF_INUSE, &sl->flags);
- slc_free_netdev(sl->dev);
- /* do not call free_netdev before rtnl_unlock */
+ slc_dealloc(sl);
rtnl_unlock();
- free_netdev(sl->dev);
return err;
err_exit:
@@ -658,9 +653,11 @@ static void slcan_close(struct tty_struct *tty)
synchronize_rcu();
flush_work(&sl->tx_work);
- /* Flush network side */
- unregister_netdev(sl->dev);
- /* This will complete via sl_free_netdev */
+ slc_close(sl->dev);
+ unregister_candev(sl->dev);
+ rtnl_lock();
+ slc_dealloc(sl);
+ rtnl_unlock();
}
static void slcan_hangup(struct tty_struct *tty)
@@ -768,14 +765,15 @@ static void __exit slcan_exit(void)
dev = slcan_devs[i];
if (!dev)
continue;
- slcan_devs[i] = NULL;
sl = netdev_priv(dev);
if (sl->tty) {
netdev_err(dev, "tty discipline still running\n");
}
- unregister_netdev(dev);
+ slc_close(dev);
+ unregister_candev(dev);
+ slc_dealloc(sl);
}
kfree(slcan_devs);
--
2.32.0
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