The only called takes ocelot_port->bridge and passes it as the "bridge"
argument to this function, which then compares it with
ocelot_port->bridge. This is not useful.

Instead, we would like this function to return 0 if ocelot_port->bridge
is not present, which is what this patch does.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20211125125808.2383984-1-vladimir.oltean@nxp.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

There is a spelling mistake in a netdev_err error message. Fix it.
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20211125002932.49217-1-colin.i.king@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

When XDP program is loaded, it is desirable that the previous TX and RX
coalesce values are not re-inited to its default value. This prevents
unnecessary re-configurig the coalesce values that were working fine
before.

Fixes: ac746c85 ("net: stmmac: enhance XDP ZC driver level switching performance")
Signed-off-by: Ong Boon Leong <boon.leong.ong@intel.com>
Tested-by: Kurt Kanzenbach <kurt@linutronix.de>
Link: https://lore.kernel.org/r/20211124114019.3949125-1-boon.leong.ong@intel.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

The node pointer is returned by of_get_child_by_name() with
refcount incremented in tsnep_mdio_init(). Calling of_node_put()
to aovid the refcount leak in tsnep_mdio_init().
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20211124084048.175456-1-yangyingliang@huawei.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

use ethtools api ethtool_sprintf to instead of snprintf.
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Link: https://lore.kernel.org/r/20211125025444.13115-1-xiangxia.m.yue@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Populate the supported interfaces bitmap and MAC capabilities mask for
the macb driver and remove the old validate implementation.
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/E1mpuRv-00D4rb-Lz@rmk-PC.armlinux.org.ukSigned-off-by: Jakub Kicinski <kuba@kernel.org>

It seems only XID 609 made it to the mass market. Therefore let's
disable detection of the other RTL8125a XID's. If nobody complains
we can remove support for RTL_GIGA_MAC_VER_60 later.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/2cd3df01-5f8b-08dd-6def-3f31a3014bde@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

This is to match ipv4 behaviour, see __ip_sock_set_tos()
implementation.

Technically for ipv6 this might not be required because normally we
do not allow tclass to influence routing, yet the cli tooling does
support it:

lpk11:~# ip -6 rule add pref 5 tos 45 lookup 5
lpk11:~# ip -6 rule
5:      from all tos 0x45 lookup 5

and in general dscp/tclass based routing does make sense.

We already have cases where dscp can affect vlan priority and/or
transmit queue (especially on wifi).

So let's just make things match.  Easier to reason about and no harm.

Cc: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Link: https://lore.kernel.org/r/20211123223208.1117871-1-zenczykowski@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

This is to match ipv4 behaviour, see __ip_sock_set_tos()
implementation at ipv4/ip_sockglue.c:579

void __ip_sock_set_tos(struct sock *sk, int val)
{
  if (sk->sk_type == SOCK_STREAM) {
    val &= ~INET_ECN_MASK;
    val |= inet_sk(sk)->tos & INET_ECN_MASK;
  }
  if (inet_sk(sk)->tos != val) {
    inet_sk(sk)->tos = val;
    sk->sk_priority = rt_tos2priority(val);
    sk_dst_reset(sk);
  }
}

Cc: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20211123223154.1117794-1-zenczykowski@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

A CAP_NET_RAW capable process can already spoof (on transmit) anything
it desires via raw packet sockets...  There is no good reason to not
allow it to also be able to play routing tricks on packets from its
own normal sockets.

There is a desire to be able to use SO_MARK for routing table selection
(via ip rule fwmark) from within a user process without having to run
it as root.  Granting it CAP_NET_RAW is much less dangerous than
CAP_NET_ADMIN (CAP_NET_RAW doesn't permit persistent state change,
while CAP_NET_ADMIN does - by for example allowing the reconfiguration
of the routing tables and/or bringing up/down devices).

Let's keep CAP_NET_ADMIN for persistent state changes,
while using CAP_NET_RAW for non-configuration related stuff.
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Link: https://lore.kernel.org/r/20211123203715.193413-1-zenczykowski@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

CAP_NET_ADMIN is and should continue to be about configuring the
system as a whole, not about configuring per-socket or per-packet
parameters.
Sending and receiving raw packets is what CAP_NET_RAW is all about.

It can already send packets with any VLAN tag, and any IPv4 TOS
mark, and any IPv6 TCLASS mark, simply by virtue of building
such a raw packet.  Not to mention using any protocol and source/
/destination ip address/port tuple.

These are the fields that networking gear uses to prioritize packets.

Hence, a CAP_NET_RAW process is already capable of affecting traffic
prioritization after it hits the wire.  This change makes it capable
of affecting traffic prioritization even in the host at the nic and
before that in the queueing disciplines (provided skb->priority is
actually being used for prioritization, and not the TOS/TCLASS field)

Hence it makes sense to allow a CAP_NET_RAW process to set the
priority of sockets and thus packets it sends.
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Link: https://lore.kernel.org/r/20211123203702.193221-1-zenczykowski@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Fix warning reported by bot.
Make sure hash is init to 0 and fix wrong logic for hash_type in
qca8k_lag_can_offload.
Reported-by: kernel test robot <lkp@intel.com>
Fixes: def97530 ("net: dsa: qca8k: add LAG support")
Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20211123154446.31019-1-ansuelsmth@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Even if firmware fails to recognize the plugged-in port module type,
allow reading port module EEPROM anyway. This helps in obtaining
necessary diagnostics information for debugging and analysis.
Signed-off-by: Manoj Malviya <manojmalviya@chelsio.com>
Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Link: https://lore.kernel.org/r/1637682437-31407-1-git-send-email-rahul.lakkireddy@chelsio.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Cited commit converted simple_strtoul() to kstrtoul() as suggested by
the former's documentation. However, it also forced all the inputs to be
decimal resulting in user space breakage.

Fix by setting the base to '0' so that the base is automatically
detected.

Before:

 # ip link add name br0 type bridge vlan_filtering 1
 # echo "0x88a8" > /sys/class/net/br0/bridge/vlan_protocol
 bash: echo: write error: Invalid argument

After:

 # ip link add name br0 type bridge vlan_filtering 1
 # echo "0x88a8" > /sys/class/net/br0/bridge/vlan_protocol
 # echo $?
 0

Fixes: 520fbdf7 ("net/bridge: replace simple_strtoul to kstrtol")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Link: https://lore.kernel.org/r/20211124101122.3321496-1-idosch@idosch.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Eric Dumazet says:

====================
gro: remove redundant rcu_read_lock

Recent trees got an increase of rcu_read_{lock|unlock} costs,
it is time to get rid of the not needed pairs.
====================

Link: https://lore.kernel.org/r/20211123225608.2155163-1-eric.dumazet@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

All gro_complete() handlers are called from napi_gro_complete()
while rcu_read_lock() has been called.

There is no point stacking more rcu_read_lock()
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

All gro_receive() handlers are called from dev_gro_receive()
while rcu_read_lock() has been called.

There is no point stacking more rcu_read_lock()
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

The following warning is fixed, by removing the unused resource size:

drivers/net/ethernet/engleder/tsnep_main.c:1155:21-24:
WARNING: Suspicious code. resource_size is maybe missing with io
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Link: https://lore.kernel.org/r/20211124205225.13985-1-gerhard@engleder-embedded.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Remove .owner field if calls are used which set it automatically

Eliminate the following coccicheck warning:
./drivers/net/ethernet/engleder/tsnep_main.c:1263:3-8: No need to set
.owner here. The core will do it.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Reviewed-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Link: https://lore.kernel.org/r/1637721384-70836-2-git-send-email-yang.lee@linux.alibaba.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Guangbin Huang says:

====================
net: hns3: updates for -next

This series includes some updates for the HNS3 ethernet driver.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

When tx timeout occurs, the info of dql maybe helpful, so print
these info to hns3_get_tx_timeo_queue_info().
Signed-off-by: Yufeng Mo <moyufeng@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Currently, there is no way to get drop packet number of multicast and
broadcast in IGU hardware module, it is not convenient to find problem
when multicast packet or broadcast packet is dropped in IGU, so this
patch adds statistics for them in debugfs.
Signed-off-by: Jie Wang <wangjie125@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Printing the whole MAC addresse may bring security risks. Therefore,
the MAC address is partially encrypted to improve security.
Signed-off-by: Yufeng Mo <moyufeng@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

When the mbx or reset message arrives, the driver is informed
through an interrupt. This task can be processed only after
the workqueue is scheduled. In some cases, this workqueue
scheduling takes a long time. As a result, the mbx or reset
service task cannot be processed in time. So add some warning
message to improve debugging efficiency for this case.
Signed-off-by: Yufeng Mo <moyufeng@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Eliminate the follow smatch warning:

drivers/net/usb/lan78xx.c:4961 lan78xx_resume() warn: inconsistent
indenting.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Kuniyuki Iwashima says:

====================
dccp/tcp: Minor fixes for inet_csk_listen_start().

The first patch removes an unused argument, and the second removes a stale
comment.
====================

Link: https://lore.kernel.org/r/20211122101622.50572-1-kuniyu@amazon.co.jpSigned-off-by: Jakub Kicinski <kuba@kernel.org>

This patch inlines dccp_listen_start() and removes a stale comment in
inet_dccp_listen() so that it looks like inet_listen().
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Reviewed-by: Richard Sailer <richard_siegfried@systemli.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

The commit 1295e2cf ("inet: minor optimization for backlog setting in
listen(2)") added change so that sk_max_ack_backlog is initialised earlier
in inet_dccp_listen() and inet_listen().  Since then, we no longer use
backlog in inet_csk_listen_start(), so let's remove it.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Reviewed-by: Richard Sailer <richard_siegfried@systemli.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

The clock domain crossing error (CDC) is calculated at every fetch of Tx or Rx
timestamps. It includes a division. Especially on arm32 based systems it is
expensive. It also requires two conditionals in the hotpath.

Add a compensation value cache to struct plat_stmmacenet_data and subtract it
unconditionally in the RX/TX functions which spares the conditionals.

The value is initialized to 0 and if supported calculated in the PTP
initialization code.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Link: https://lore.kernel.org/r/20211122111931.135135-1-kurt@linutronix.deSigned-off-by: Jakub Kicinski <kuba@kernel.org>

.ndo_change_proto_down was added seemingly to enable out-of-tree
implementations. Over 2.5yrs later we still have no real users
upstream. Hardwire the generic implementation for now, we can
revert once real users materialize. (rocker is a test vehicle,
not a user.)

We need to drop the optimization on the sysfs side, because
unlike ndos priv_flags will be changed at runtime, so we'd
need READ_ONCE/WRITE_ONCE everywhere..
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Tony Nguyen says:

====================
100GbE Intel Wired LAN Driver Updates 2021-11-22

Shiraz Saleem says:

Currently E800 devices come up as RoCEv2 devices by default.

This series add supports for users to configure iWARP or RoCEv2 functionality
per PCI function. devlink parameters is used to realize this and is keyed
off similar work in [1].

[1] https://lore.kernel.org/linux-rdma/20210810132424.9129-1-parav@nvidia.com/
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Marek Behún says:

====================
Add 5gbase-r support for mvpp2

this adds support for 5gbase-r for mvpp2 driver. Current versions of
TF-A firmware support changing the PHY to 5gbase-r via SMC calls, at
least on Macchiatobin.

Tested on Macchiatobin.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Add support for PHY_INTERFACE_MODE_5GBASER.
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add support for PHY_INTERFACE_MODE_5GBASER mode within the Marvell CP110
common PHY driver.

This is currently only supported via SMC calls to TF-A. Legacy support
may be added later, if needed.
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Commit 4dfb9982 ("tsn:  Fix build.") fixed compilation with const
dev_addr. In tsnep_netdev_set_mac_address() the call of ether_addr_copy()
was replaced with dev_set_mac_address(), which calls
ndo_set_mac_address(). This results in an endless recursive loop because
ndo_set_mac_address is set to tsnep_netdev_set_mac_address.

Call eth_hw_addr_set() instead of dev_set_mac_address() in
ndo_set_mac_address()/tsnep_netdev_set_mac_address() to copy the address
as intended.

[   26.563303] Insufficient stack space to handle exception!
[   26.563312] ESR: 0x96000047 -- DABT (current EL)
[   26.563317] FAR: 0xffff80000a507fc0
[   26.563320] Task stack:     [0xffff80000a508000..0xffff80000a50c000]
[   26.563324] IRQ stack:      [0xffff80000a0c0000..0xffff80000a0c4000]
[   26.563327] Overflow stack: [0xffff00007fbaf2b0..0xffff00007fbb02b0]
[   26.563333] CPU: 3 PID: 381 Comm: ifconfig Not tainted 5.16.0-rc1-zynqmp #60
[   26.563340] Hardware name: TSN endpoint (DT)
[   26.563343] pstate: a0000005 (NzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[   26.563351] pc : inetdev_event+0x4/0x560
[   26.563364] lr : raw_notifier_call_chain+0x54/0x78
[   26.563372] sp : ffff80000a508040
[   26.563374] x29: ffff80000a508040 x28: ffff00000132b800 x27: 0000000000000000
[   26.563386] x26: 0000000000000000 x25: ffff800000ea5058 x24: 0904030201020001
[   26.563396] x23: ffff800000ea5058 x22: ffff80000a5080e0 x21: 0000000000000009
[   26.563405] x20: 00000000fffffffa x19: ffff80000a009510 x18: 0000000000000000
[   26.563414] x17: 0000000000000000 x16: 0000000000000000 x15: 0000ffffd1341030
[   26.563422] x14: ffffffffffffffff x13: 0000000000000020 x12: 0101010101010101
[   26.563432] x11: 0000000000000020 x10: 0101010101010101 x9 : 7f7f7f7f7f7f7f7f
[   26.563441] x8 : 7f7f7f7f7f7f7f7f x7 : fefefeff30677364 x6 : 0000000080808080
[   26.563450] x5 : 0000000000000000 x4 : ffff800008dee170 x3 : ffff80000a50bd42
[   26.563459] x2 : ffff80000a5080e0 x1 : 0000000000000009 x0 : ffff80000a0092d0
[   26.563470] Kernel panic - not syncing: kernel stack overflow
[   26.563474] CPU: 3 PID: 381 Comm: ifconfig Not tainted 5.16.0-rc1-zynqmp #60
[   26.563481] Hardware name: TSN endpoint (DT)
[   26.563484] Call trace:
[   26.563486]  dump_backtrace+0x0/0x1b0
[   26.563497]  show_stack+0x18/0x68
[   26.563504]  dump_stack_lvl+0x68/0x84
[   26.563513]  dump_stack+0x18/0x34
[   26.563519]  panic+0x164/0x324
[   26.563524]  nmi_panic+0x64/0x98
[   26.563533]  panic_bad_stack+0x108/0x128
[   2k6.563539]  handle_bad_stack+0x38/0x68
[   26.563548]  __bad_stack+0x88/0x8c
[   26.563553]  inetdev_event+0x4/0x560
[   26.563560]  call_netdevice_notifiers_info+0x58/0xa8
[   26.563569]  dev_set_mac_address+0x78/0x110
[   26.563576]  tsnep_netdev_set_mac_address+0x38/0x60 [tsnep]
[   26.563591]  dev_set_mac_address+0xc4/0x110
[   26.563599]  tsnep_netdev_set_mac_address+0x38/0x60 [tsnep]
...
[   26.565444]  dev_set_mac_address+0xc4/0x110
[   26.565452]  tsnep_netdev_set_mac_address+0x38/0x60 [tsnep]
[   26.565462]  dev_set_mac_address+0xc4/0x110
[   26.565469]  dev_set_mac_address_user+0x44/0x68
[   26.565477]  dev_ifsioc+0x30c/0x568
[   26.565483]  dev_ioctl+0x124/0x3f0
[   26.565489]  sock_do_ioctl+0xb4/0xf8
[   26.565497]  sock_ioctl+0x2f4/0x398
[   26.565503]  __arm64_sys_ioctl+0xa8/0xe8
[   26.565511]  invoke_syscall+0x44/0x108
[   26.565520]  el0_svc_common.constprop.3+0x94/0xf8
[   26.565527]  do_el0_svc+0x24/0x88
[   26.565534]  el0_svc+0x20/0x50
[   26.565541]  el0t_64_sync_handler+0x90/0xb8
[   26.565548]  el0t_64_sync+0x180/0x184
[   26.565556] SMP: stopping secondary CPUs
[   26.565622] Kernel Offset: disabled
[   26.565624] CPU features: 0x0,00004002,00000846
[   26.565628] Memory Limit: none
[   27.843428] ---[ end Kernel panic - not syncing: kernel stack overflow ]---

Fixes: 4dfb9982 ("tsn:  Fix build.")
Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Ansuel Smith says:

====================
Add mirror and LAG support to qca8k

With the continue of adding 'Multiple feature to qca8k'

The switch supports mirror mode and LAG.
In mirror mode a port is set as mirror and other port are configured
to both igress or egress mode. With no port configured for mirror,
the mirror port is disabled and reverted to normal port.

The switch supports max 4 LAG with 4 different member max.
Current supported mode is Hash mode in both L2 or L2+3 mode.
There is a problematic implementation for the hash mode where
with multiple LAG configured, someone has to remove them to
change the hash mode as it's global.
When a member of the LAG is disconnected, the traffic is redirected
to the other port.

Some warning are present from checkpatch but can't really be fixed
as it would result in making the regs less readable.
(They really did their best with the LAG reg logic and complexity)
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Add LAG support to this switch. In Documentation this is described as
trunk mode. A max of 4 LAGs are supported and each can support up to 4
port. The current tx mode supported is Hash mode with both L2 and L2+3
mode.
When no port are present in the trunk, the trunk is disabled in the
switch.
When a port is disconnected, the traffic is redirected to the other
available port.
The hash mode is global and each LAG require to have the same hash mode
set. To change the hash mode when multiple LAG are configured, it's
required to remove each LAG and set the desired hash mode to the last.
An error is printed when it's asked to set a not supported hadh mode.
Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The switch supports mirror mode. Only one port can set as mirror port and
every other port can set to both ingress and egress mode. The mirror
port is disabled and reverted to normal operation once every port is
removed from sending packet to it.
Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add neigh_confirm() for the confirmed member in struct neighbour,
it can be called as an independent unit by other functions.
Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This change adds a MCTP Serial transport binding, as defined by DMTF
specificiation DSP0253 - "MCTP Serial Transport Binding". This is
implemented as a new serial line discipline, and can be attached to
arbitrary tty devices.

From the Kconfig description:

  This driver provides an MCTP-over-serial interface, through a
  serial line-discipline, as defined by DMTF specification "DSP0253 -
  MCTP Serial Transport Binding". By attaching the ldisc to a serial
  device, we get a new net device to transport MCTP packets.

  This allows communication with external MCTP endpoints which use
  serial as their transport. It can also be used as an easy way to
  provide MCTP connectivity between virtual machines, by forwarding
  data between simple virtual serial devices.

  Say y here if you need to connect to MCTP endpoints over serial. To
  compile as a module, use m; the module will be called mctp-serial.

Once the N_MCTP line discipline is set [using ioctl(TCIOSETD)], we get a
new netdev suitable for MCTP communication.

The 'mctp' utility[1] provides a simple wrapper for this ioctl, using
'link serial <device>':

  # mctp link serial /dev/ttyS0 &
  # mctp link
  dev lo index 1 address 0x00:00:00:00:00:00 net 1 mtu 65536 up
  dev mctpserial0 index 5 address 0x(no-addr) net 1 mtu 68 down

[1]: https://github.com/CodeConstruct/mctpSigned-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>