[PATCH 1/3] Revert "can: raw: instantly reject unsupported CAN frames"

[Oliver Hartkopp <socketcan@hartkopp.net>]

This reverts commit 1a620a723853a0f49703c317d52dc6b9602cbaa8

and its follow-up fixes for the introduced dependency issues.

commit 1a620a723853 ("can: raw: instantly reject unsupported CAN frames")
commit cb2dc6d2869a ("can: Kconfig: select CAN driver infrastructure by default")
commit 6abd4577bccc ("can: fix build dependency")
commit 5a5aff6338c0 ("can: fix build dependency")

The entire problem was caused by the requirement that a new network layer
feature needed to know about the protocol capabilities of the CAN devices.
Instead of accessing CAN device internal data structures which caused the
dependency problems a better approach has been developed which makes use of
CAN specific ml_priv data which is accessible from both sides.

Cc: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
 drivers/net/can/Kconfig      |  7 +++--
 drivers/net/can/Makefile     |  2 +-
 drivers/net/can/dev/Makefile |  5 ++--
 include/linux/can/dev.h      |  7 -----
 net/can/raw.c                | 54 ++++++------------------------------
 5 files changed, 17 insertions(+), 58 deletions(-)

diff --git a/drivers/net/can/Kconfig b/drivers/net/can/Kconfig
index cfaea6178a71..e15e320db476 100644
--- a/drivers/net/can/Kconfig
+++ b/drivers/net/can/Kconfig
@@ -1,9 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
 menuconfig CAN_DEV
-	bool "CAN Device Drivers"
+	tristate "CAN Device Drivers"
 	default y
 	depends on CAN
 	help
 	  Controller Area Network (CAN) is serial communications protocol up to
 	  1Mbit/s for its original release (now known as Classical CAN) and up
@@ -15,11 +15,14 @@ menuconfig CAN_DEV
 
 	  This section contains all the CAN(-FD) device drivers including the
 	  virtual ones. If you own such devices or plan to use the virtual CAN
 	  interfaces to develop applications, say Y here.
 
-if CAN_DEV && CAN
+	  To compile as a module, choose M here: the module will be called
+	  can-dev.
+
+if CAN_DEV
 
 config CAN_VCAN
 	tristate "Virtual Local CAN Interface (vcan)"
 	help
 	  Similar to the network loopback devices, vcan offers a
diff --git a/drivers/net/can/Makefile b/drivers/net/can/Makefile
index 37e2f1a2faec..d7bc10a6b8ea 100644
--- a/drivers/net/can/Makefile
+++ b/drivers/net/can/Makefile
@@ -5,11 +5,11 @@
 
 obj-$(CONFIG_CAN_VCAN)		+= vcan.o
 obj-$(CONFIG_CAN_VXCAN)		+= vxcan.o
 obj-$(CONFIG_CAN_SLCAN)		+= slcan/
 
-obj-$(CONFIG_CAN_DEV)		+= dev/
+obj-y				+= dev/
 obj-y				+= esd/
 obj-y				+= rcar/
 obj-y				+= rockchip/
 obj-y				+= spi/
 obj-y				+= usb/
diff --git a/drivers/net/can/dev/Makefile b/drivers/net/can/dev/Makefile
index 64226acf0f3d..633687d6b6c0 100644
--- a/drivers/net/can/dev/Makefile
+++ b/drivers/net/can/dev/Makefile
@@ -1,10 +1,11 @@
 # SPDX-License-Identifier: GPL-2.0
 
-obj-$(CONFIG_CAN) += can-dev.o
+obj-$(CONFIG_CAN_DEV) += can-dev.o
+
+can-dev-y += skb.o
 
-can-dev-$(CONFIG_CAN_DEV) += skb.o
 can-dev-$(CONFIG_CAN_CALC_BITTIMING) += calc_bittiming.o
 can-dev-$(CONFIG_CAN_NETLINK) += bittiming.o
 can-dev-$(CONFIG_CAN_NETLINK) += dev.o
 can-dev-$(CONFIG_CAN_NETLINK) += length.o
 can-dev-$(CONFIG_CAN_NETLINK) += netlink.o
diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index f6416a56e95d..52c8be5c160e 100644
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -109,18 +109,11 @@ struct net_device *alloc_candev_mqs(int sizeof_priv, unsigned int echo_skb_max,
 #define alloc_candev_mq(sizeof_priv, echo_skb_max, count) \
 	alloc_candev_mqs(sizeof_priv, echo_skb_max, count, count)
 void free_candev(struct net_device *dev);
 
 /* a candev safe wrapper around netdev_priv */
-#if IS_ENABLED(CONFIG_CAN_NETLINK)
 struct can_priv *safe_candev_priv(struct net_device *dev);
-#else
-static inline struct can_priv *safe_candev_priv(struct net_device *dev)
-{
-	return NULL;
-}
-#endif
 
 int open_candev(struct net_device *dev);
 void close_candev(struct net_device *dev);
 void can_set_default_mtu(struct net_device *dev);
 int __must_check can_set_static_ctrlmode(struct net_device *dev,
diff --git a/net/can/raw.c b/net/can/raw.c
index be1ef7cf4204..f36a83d3447c 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -890,62 +890,24 @@ static void raw_put_canxl_vcid(struct raw_sock *ro, struct sk_buff *skb)
 		cxl->prio &= CANXL_PRIO_MASK;
 		cxl->prio |= ro->tx_vcid_shifted;
 	}
 }
 
-static inline bool raw_dev_cc_enabled(struct net_device *dev,
-				      struct can_priv *priv)
+static unsigned int raw_check_txframe(struct raw_sock *ro, struct sk_buff *skb, int mtu)
 {
-	/* The CANXL-only mode disables error-signalling on the CAN bus
-	 * which is needed to send CAN CC/FD frames
-	 */
-	if (priv)
-		return !can_dev_in_xl_only_mode(priv);
-
-	/* virtual CAN interfaces always support CAN CC */
-	return true;
-}
-
-static inline bool raw_dev_fd_enabled(struct net_device *dev,
-				      struct can_priv *priv)
-{
-	/* check FD ctrlmode on real CAN interfaces */
-	if (priv)
-		return (priv->ctrlmode & CAN_CTRLMODE_FD);
-
-	/* check MTU for virtual CAN FD interfaces */
-	return (READ_ONCE(dev->mtu) >= CANFD_MTU);
-}
-
-static inline bool raw_dev_xl_enabled(struct net_device *dev,
-				      struct can_priv *priv)
-{
-	/* check XL ctrlmode on real CAN interfaces */
-	if (priv)
-		return (priv->ctrlmode & CAN_CTRLMODE_XL);
-
-	/* check MTU for virtual CAN XL interfaces */
-	return can_is_canxl_dev_mtu(READ_ONCE(dev->mtu));
-}
-
-static unsigned int raw_check_txframe(struct raw_sock *ro, struct sk_buff *skb,
-				      struct net_device *dev)
-{
-	struct can_priv *priv = safe_candev_priv(dev);
-
-	/* Classical CAN */
-	if (can_is_can_skb(skb) && raw_dev_cc_enabled(dev, priv))
+	/* Classical CAN -> no checks for flags and device capabilities */
+	if (can_is_can_skb(skb))
 		return CAN_MTU;
 
-	/* CAN FD */
+	/* CAN FD -> needs to be enabled and a CAN FD or CAN XL device */
 	if (ro->fd_frames && can_is_canfd_skb(skb) &&
-	    raw_dev_fd_enabled(dev, priv))
+	    (mtu == CANFD_MTU || can_is_canxl_dev_mtu(mtu)))
 		return CANFD_MTU;
 
-	/* CAN XL */
+	/* CAN XL -> needs to be enabled and a CAN XL device */
 	if (ro->xl_frames && can_is_canxl_skb(skb) &&
-	    raw_dev_xl_enabled(dev, priv))
+	    can_is_canxl_dev_mtu(mtu))
 		return CANXL_MTU;
 
 	return 0;
 }
 
@@ -997,11 +959,11 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 		goto free_skb;
 
 	err = -EINVAL;
 
 	/* check for valid CAN (CC/FD/XL) frame content */
-	txmtu = raw_check_txframe(ro, skb, dev);
+	txmtu = raw_check_txframe(ro, skb, READ_ONCE(dev->mtu));
 	if (!txmtu)
 		goto free_skb;
 
 	/* only CANXL: clear/forward/set VCID value */
 	if (txmtu == CANXL_MTU)
-- 
2.47.3