net: dsa: implement get_ts_stats ethtool operation for user ports

Integrate with the standard infrastructure for reporting hardware packet
timestamping statistics.

Signed-off-by: Vladimir Oltean <v

net: dsa: implement get_ts_stats ethtool operation for user ports

Integrate with the standard infrastructure for reporting hardware packet
timestamping statistics.

Signed-off-by: Vladimir Oltean <[email protected]>
Reviewed-by: Jakub Kicinski <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

net: dsa: remove get_mac_eee() method

The get_mac_eee() is no longer called by the core DSA code, nor are
there any implementations of this method. Remove it.

Signed-off-by: Russell King (Oracle) <

net: dsa: remove get_mac_eee() method

The get_mac_eee() is no longer called by the core DSA code, nor are
there any implementations of this method. Remove it.

Signed-off-by: Russell King (Oracle) <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

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net: dsa: provide implementation of .support_eee()

Provide a trivial implementation for the .support_eee() method which
switch drivers can use to simply indicate that they support EEE on
all their u

net: dsa: provide implementation of .support_eee()

Provide a trivial implementation for the .support_eee() method which
switch drivers can use to simply indicate that they support EEE on
all their user ports.

Signed-off-by: Russell King (Oracle) <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
Reviewed-by: Vladimir Oltean <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

net: dsa: add hook to determine whether EEE is supported

Add a hook to determine whether the switch supports EEE. This will
return false if the switch does not, or true if it does. If the
method is

net: dsa: add hook to determine whether EEE is supported

Add a hook to determine whether the switch supports EEE. This will
return false if the switch does not, or true if it does. If the
method is not implemented, we assume (currently) that the switch
supports EEE.

Signed-off-by: Russell King (Oracle) <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
Reviewed-by: Vladimir Oltean <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

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net: dsa: remove obsolete phylink dsa_switch operations

No driver now uses the DSA switch phylink members, so we can now remove
the method pointers, but we need to leave empty shim functions to allo

net: dsa: remove obsolete phylink dsa_switch operations

No driver now uses the DSA switch phylink members, so we can now remove
the method pointers, but we need to leave empty shim functions to allow
those drivers that do not provide phylink MAC operations structure to
continue functioning.

Signed-off-by: Russell King (oracle) <[email protected]>
Reviewed-by: Vladimir Oltean <[email protected]>
Tested-by: Vladimir Oltean <[email protected]> # sja1105, felix, dsa_loop
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

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net: dsa: provide a software untagging function on RX for VLAN-aware bridges

Through code analysis, I realized that the ds->untag_bridge_pvid logic
is contradictory - see the newly added FIXME above

net: dsa: provide a software untagging function on RX for VLAN-aware bridges

Through code analysis, I realized that the ds->untag_bridge_pvid logic
is contradictory - see the newly added FIXME above the kernel-doc for
dsa_software_untag_vlan_unaware_bridge().

Moreover, for the Felix driver, I need something very similar, but which
is actually _not_ contradictory: untag the bridge PVID on RX, but for
VLAN-aware bridges. The existing logic does it for VLAN-unaware bridges.

Since I don't want to change the functionality of drivers which were
supposedly properly tested with the ds->untag_bridge_pvid flag, I have
introduced a new one: ds->untag_vlan_aware_bridge_pvid, and I have
refactored the DSA reception code into a common path for both flags.

TODO: both flags should be unified under a single ds->software_vlan_untag,
which users of both current flags should set. This is not something that
can be carried out right away. It needs very careful examination of all
drivers which make use of this functionality, since some of them
actually get this wrong in the first place.

For example, commit 9130c2d30c17 ("net: dsa: microchip: ksz8795: Use
software untagging on CPU port") uses this in a driver which has
ds->configure_vlan_while_not_filtering = true. The latter mechanism has
been known for many years to be broken by design:
https://lore.kernel.org/netdev/CABumfLzJmXDN_W-8Z=p9KyKUVi_HhS7o_poBkeKHS2BkAiyYpw@mail.gmail.com/
and we have the situation of 2 bugs canceling each other. There is no
private VLAN, and the port follows the PVID of the VLAN-unaware bridge.
So, it's kinda ok for that driver to use the ds->untag_bridge_pvid
mechanism, in a broken way.

Signed-off-by: Vladimir Oltean <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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net: Add struct kernel_ethtool_ts_info

In prevision to add new UAPI for hwtstamp we will be limited to the struct
ethtool_ts_info that is currently passed in fixed binary format through the
ETHTOOL_

net: Add struct kernel_ethtool_ts_info

In prevision to add new UAPI for hwtstamp we will be limited to the struct
ethtool_ts_info that is currently passed in fixed binary format through the
ETHTOOL_GET_TS_INFO ethtool ioctl. It would be good if new kernel code
already started operating on an extensible kernel variant of that
structure, similar in concept to struct kernel_hwtstamp_config vs struct
hwtstamp_config.

Since struct ethtool_ts_info is in include/uapi/linux/ethtool.h, here
we introduce the kernel-only structure in include/linux/ethtool.h.
The manual copy is then made in the function called by ETHTOOL_GET_TS_INFO.

Acked-by: Shannon Nelson <[email protected]>
Acked-by: Alexandra Winter <[email protected]>
Signed-off-by: Kory Maincent <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

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net: dsa: vsc73xx: introduce tag 8021q for vsc73xx

This commit introduces a new tagger based on 802.1q tagging.
It's designed for the vsc73xx driver. The VSC73xx family doesn't have
any tag support

net: dsa: vsc73xx: introduce tag 8021q for vsc73xx

This commit introduces a new tagger based on 802.1q tagging.
It's designed for the vsc73xx driver. The VSC73xx family doesn't have
any tag support for the RGMII port, but it could be based on VLANs.

Reviewed-by: Florian Fainelli <[email protected]>
Reviewed-by: Vladimir Oltean <[email protected]>
Signed-off-by: Pawel Dembicki <[email protected]>
Reviewed-by: Linus Walleij <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

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net: dsa: remove mac_prepare()/mac_finish() shims

No DSA driver makes use of the mac_prepare()/mac_finish() shimmed
operations anymore, so we can remove these.

Signed-off-by: Russell King (Oracle)

net: dsa: remove mac_prepare()/mac_finish() shims

No DSA driver makes use of the mac_prepare()/mac_finish() shimmed
operations anymore, so we can remove these.

Signed-off-by: Russell King (Oracle) <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

net: dsa: add support switches global DSCP priority mapping

Some switches like Microchip KSZ variants do not support per port DSCP
priority configuration. Instead there is a global DSCP mapping tabl

net: dsa: add support switches global DSCP priority mapping

Some switches like Microchip KSZ variants do not support per port DSCP
priority configuration. Instead there is a global DSCP mapping table.

To handle it, we will accept set/del request to any of user ports to
make global configuration and update dcb app entries for all other
ports.

Signed-off-by: Oleksij Rempel <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

show more ...

net: dsa: add support for DCB get/set apptrust configuration

Add DCB support to get/set trust configuration for different packet
priority information sources. Some switch allow to chose different
so

net: dsa: add support for DCB get/set apptrust configuration

Add DCB support to get/set trust configuration for different packet
priority information sources. Some switch allow to chose different
source of packet priority classification. For example on KSZ switches it
is possible to configure VLAN PCP and/or DSCP sources.

Signed-off-by: Oleksij Rempel <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

show more ...

net: dsa: Remove adjust_link paths

Now that we no longer any drivers using PHYLIB's adjust_link callback,
remove all paths that made use of adjust_link as well as the associated
functions.

Signed-o

net: dsa: Remove adjust_link paths

Now that we no longer any drivers using PHYLIB's adjust_link callback,
remove all paths that made use of adjust_link as well as the associated
functions.

Signed-off-by: Florian Fainelli <[email protected]>
Reviewed-by: Russell King (Oracle) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

net: dsa: Remove fixed_link_update member

We have not had a switch driver use a fixed_link_update callback since
58d56fcc3964f9be0a9ca42fd126bcd9dc7afc90 ("net: dsa: bcm_sf2: Get rid of
PHYLIB funct

net: dsa: Remove fixed_link_update member

We have not had a switch driver use a fixed_link_update callback since
58d56fcc3964f9be0a9ca42fd126bcd9dc7afc90 ("net: dsa: bcm_sf2: Get rid of
PHYLIB functions") remove this callback.

Signed-off-by: Florian Fainelli <[email protected]>
Reviewed-by: Russell King (Oracle) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

devlink: extend devlink_param *set pointer

Extend devlink_param *set function pointer to take extack as a param.
Sometimes it is needed to pass information to the end user from set
function. It is m

devlink: extend devlink_param *set pointer

Extend devlink_param *set function pointer to take extack as a param.
Sometimes it is needed to pass information to the end user from set
function. It is more proper to use for that netlink instead of passing
message to dmesg.

Reviewed-by: Jiri Pirko <[email protected]>
Reviewed-by: Przemek Kitszel <[email protected]>
Signed-off-by: Mateusz Polchlopek <[email protected]>
Signed-off-by: Tony Nguyen <[email protected]>

show more ...

net: dsa: allow DSA switch drivers to provide their own phylink mac ops

Rather than having a shim for each and every phylink MAC operation,
allow DSA switch drivers to provide their own ops structur

net: dsa: allow DSA switch drivers to provide their own phylink mac ops

Rather than having a shim for each and every phylink MAC operation,
allow DSA switch drivers to provide their own ops structure. When a
DSA driver provides the phylink MAC operations, the shimmed ops must
not be provided, so fail an attempt to register a switch with both
the phylink_mac_ops in struct dsa_switch and the phylink_mac_*
operations populated in dsa_switch_ops populated.

Signed-off-by: Russell King (Oracle) <[email protected]>
Reviewed-by: Vladimir Oltean <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

net: dsa: introduce dsa_phylink_to_port()

We convert from a phylink_config struct to a dsa_port struct in many
places, let's provide a helper for this.

Reviewed-by: Andrew Lunn <[email protected]>
Rev

net: dsa: introduce dsa_phylink_to_port()

We convert from a phylink_config struct to a dsa_port struct in many
places, let's provide a helper for this.

Reviewed-by: Andrew Lunn <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
Signed-off-by: Russell King (Oracle) <[email protected]>
Reviewed-by: Vladimir Oltean <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

ethtool: replace struct ethtool_eee with a new struct ethtool_keee on kernel side

In order to pass EEE link modes beyond bit 32 to userspace we have to
complement the 32 bit bitmaps in struct ethtoo

ethtool: replace struct ethtool_eee with a new struct ethtool_keee on kernel side

In order to pass EEE link modes beyond bit 32 to userspace we have to
complement the 32 bit bitmaps in struct ethtool_eee with linkmode
bitmaps. Therefore, similar to ethtool_link_settings and
ethtool_link_ksettings, add a struct ethtool_keee. In a first step
it's an identical copy of ethtool_eee. This patch simply does a
s/ethtool_eee/ethtool_keee/g for all users.
No functional change intended.

Suggested-by: Andrew Lunn <[email protected]>
Signed-off-by: Heiner Kallweit <[email protected]>
Reviewed-by: Andrew Lunn <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

show more ...

net: dsa: Use conduit and user terms

Use more inclusive terms throughout the DSA subsystem by moving away
from "master" which is replaced by "conduit" and "slave" which is
replaced by "user". No fun

net: dsa: Use conduit and user terms

Use more inclusive terms throughout the DSA subsystem by moving away
from "master" which is replaced by "conduit" and "slave" which is
replaced by "user". No functional changes.

Acked-by: Rob Herring <[email protected]>
Acked-by: Stephen Hemminger <[email protected]>
Reviewed-by: Vladimir Oltean <[email protected]>
Signed-off-by: Florian Fainelli <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

net: dsa: notify drivers of MAC address changes on user ports

In some cases, drivers may need to veto the changing of a MAC address on
a user port. Such is the case with KSZ9477 when it offloads a H

net: dsa: notify drivers of MAC address changes on user ports

In some cases, drivers may need to veto the changing of a MAC address on
a user port. Such is the case with KSZ9477 when it offloads a HSR device,
because it programs the MAC address of multiple ports to a shared
hardware register. Those ports need to have equal MAC addresses for the
lifetime of the HSR offload.

Signed-off-by: Vladimir Oltean <[email protected]>
Signed-off-by: Lukasz Majewski <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
Reviewed-by: Vladimir Oltean <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>

show more ...

net: dsa: propagate extack to ds->ops->port_hsr_join()

Drivers can provide meaningful error messages which state a reason why
they can't perform an offload, and dsa_slave_changeupper() already has
t

net: dsa: propagate extack to ds->ops->port_hsr_join()

Drivers can provide meaningful error messages which state a reason why
they can't perform an offload, and dsa_slave_changeupper() already has
the infrastructure to propagate these over netlink rather than printing
to the kernel log. So pass the extack argument and modify the xrs700x
driver's port_hsr_join() prototype.

Also take the opportunity and use the extack for the 2 -EOPNOTSUPP cases
from xrs700x_hsr_join().

Signed-off-by: Vladimir Oltean <[email protected]>
Signed-off-by: Lukasz Majewski <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
Reviewed-by: Vladimir Oltean <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>

show more ...

net: dsa: remove legacy_pre_march2020 detection

All drivers are now updated for the March 2020 changes, and no longer
make use of the mac_pcs_get_state() or mac_an_restart() operations,
which are no

net: dsa: remove legacy_pre_march2020 detection

All drivers are now updated for the March 2020 changes, and no longer
make use of the mac_pcs_get_state() or mac_an_restart() operations,
which are now NULL across all DSA drivers. All DSA drivers don't look
at speed, duplex, pause or advertisement in their phylink_mac_config()
method either.

Remove support for these operations from DSA, and stop marking DSA as
a legacy driver by default.

Signed-off-by: Russell King (Oracle) <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
Reviewed-by: Vladimir Oltean <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>

show more ...

net: dsa: avoid suspicious RCU usage for synced VLAN-aware MAC addresses

When using the felix driver (the only one which supports UC filtering
and MC filtering) as a DSA master for a random other DS

net: dsa: avoid suspicious RCU usage for synced VLAN-aware MAC addresses

When using the felix driver (the only one which supports UC filtering
and MC filtering) as a DSA master for a random other DSA switch, one can
see the following stack trace when the downstream switch ports join a
VLAN-aware bridge:

=============================
WARNING: suspicious RCU usage
-----------------------------
net/8021q/vlan_core.c:238 suspicious rcu_dereference_protected() usage!

stack backtrace:
Workqueue: dsa_ordered dsa_slave_switchdev_event_work
Call trace:
lockdep_rcu_suspicious+0x170/0x210
vlan_for_each+0x8c/0x188
dsa_slave_sync_uc+0x128/0x178
__hw_addr_sync_dev+0x138/0x158
dsa_slave_set_rx_mode+0x58/0x70
__dev_set_rx_mode+0x88/0xa8
dev_uc_add+0x74/0xa0
dsa_port_bridge_host_fdb_add+0xec/0x180
dsa_slave_switchdev_event_work+0x7c/0x1c8
process_one_work+0x290/0x568

What it's saying is that vlan_for_each() expects rtnl_lock() context and
it's not getting it, when it's called from the DSA master's ndo_set_rx_mode().

The caller of that - dsa_slave_set_rx_mode() - is the slave DSA
interface's dsa_port_bridge_host_fdb_add() which comes from the deferred
dsa_slave_switchdev_event_work().

We went to great lengths to avoid the rtnl_lock() context in that call
path in commit 0faf890fc519 ("net: dsa: drop rtnl_lock from
dsa_slave_switchdev_event_work"), and calling rtnl_lock() is simply not
an option due to the possibility of deadlocking when calling
dsa_flush_workqueue() from the call paths that do hold rtnl_lock() -
basically all of them.

So, when the DSA master calls vlan_for_each() from its ndo_set_rx_mode(),
the state of the 8021q driver on this device is really not protected
from concurrent access by anything.

Looking at net/8021q/, I don't think that vlan_info->vid_list was
particularly designed with RCU traversal in mind, so introducing an RCU
read-side form of vlan_for_each() - vlan_for_each_rcu() - won't be so
easy, and it also wouldn't be exactly what we need anyway.

In general I believe that the solution isn't in net/8021q/ anyway;
vlan_for_each() is not cut out for this task. DSA doesn't need rtnl_lock()
to be held per se - since it's not a netdev state change that we're
blocking, but rather, just concurrent additions/removals to a VLAN list.
We don't even need sleepable context - the callback of vlan_for_each()
just schedules deferred work.

The proposed escape is to remove the dependency on vlan_for_each() and
to open-code a non-sleepable, rtnl-free alternative to that, based on
copies of the VLAN list modified from .ndo_vlan_rx_add_vid() and
.ndo_vlan_rx_kill_vid().

Fixes: 64fdc5f341db ("net: dsa: sync unicast and multicast addresses for VLAN filters too")
Signed-off-by: Vladimir Oltean <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

net: dsa: introduce preferred_default_local_cpu_port and use on MT7530

Since the introduction of the OF bindings, DSA has always had a policy that
in case multiple CPU ports are present in the devic

net: dsa: introduce preferred_default_local_cpu_port and use on MT7530

Since the introduction of the OF bindings, DSA has always had a policy that
in case multiple CPU ports are present in the device tree, the numerically
smallest one is always chosen.

The MT7530 switch family, except the switch on the MT7988 SoC, has 2 CPU
ports, 5 and 6, where port 6 is preferable on the MT7531BE switch because
it has higher bandwidth.

The MT7530 driver developers had 3 options:
- to modify DSA when the MT7531 switch support was introduced, such as to
prefer the better port
- to declare both CPU ports in device trees as CPU ports, and live with the
sub-optimal performance resulting from not preferring the better port
- to declare just port 6 in the device tree as a CPU port

Of course they chose the path of least resistance (3rd option), kicking the
can down the road. The hardware description in the device tree is supposed
to be stable - developers are not supposed to adopt the strategy of
piecemeal hardware description, where the device tree is updated in
lockstep with the features that the kernel currently supports.

Now, as a result of the fact that they did that, any attempts to modify the
device tree and describe both CPU ports as CPU ports would make DSA change
its default selection from port 6 to 5, effectively resulting in a
performance degradation visible to users with the MT7531BE switch as can be
seen below.

Without preferring port 6:

[ ID][Role] Interval Transfer Bitrate Retr
[ 5][TX-C] 0.00-20.00 sec 374 MBytes 157 Mbits/sec 734 sender
[ 5][TX-C] 0.00-20.00 sec 373 MBytes 156 Mbits/sec receiver
[ 7][RX-C] 0.00-20.00 sec 1.81 GBytes 778 Mbits/sec 0 sender
[ 7][RX-C] 0.00-20.00 sec 1.81 GBytes 777 Mbits/sec receiver

With preferring port 6:

[ ID][Role] Interval Transfer Bitrate Retr
[ 5][TX-C] 0.00-20.00 sec 1.99 GBytes 856 Mbits/sec 273 sender
[ 5][TX-C] 0.00-20.00 sec 1.99 GBytes 855 Mbits/sec receiver
[ 7][RX-C] 0.00-20.00 sec 1.72 GBytes 737 Mbits/sec 15 sender
[ 7][RX-C] 0.00-20.00 sec 1.71 GBytes 736 Mbits/sec receiver

Using one port for WAN and the other ports for LAN is a very popular use
case which is what this test emulates.

As such, this change proposes that we retroactively modify stable kernels
(which don't support the modification of the CPU port assignments, so as to
let user space fix the problem and restore the throughput) to keep the
mt7530 driver preferring port 6 even with device trees where the hardware
is more fully described.

Fixes: c288575f7810 ("net: dsa: mt7530: Add the support of MT7531 switch")
Signed-off-by: Vladimir Oltean <[email protected]>
Signed-off-by: Arınç ÜNAL <[email protected]>
Reviewed-by: Russell King (Oracle) <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

show more ...

net: dsa: add support for mac_prepare() and mac_finish() calls

Add DSA support for the phylink mac_prepare() and mac_finish() calls.
These were introduced as part of the PCS support to allow MACs to

net: dsa: add support for mac_prepare() and mac_finish() calls

Add DSA support for the phylink mac_prepare() and mac_finish() calls.
These were introduced as part of the PCS support to allow MACs to
perform preparatory steps prior to configuration, and finalisation
steps after the MAC and PCS has been configured.

Introducing phylink_pcs support to the mv88e6xxx DSA driver needs some
code moved out of its mac_config() stage into the mac_prepare() and
mac_finish() stages, and this commit facilitates such code in DSA
drivers.

Reviewed-by: Andrew Lunn <[email protected]>
Signed-off-by: Russell King (Oracle) <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

show more ...

net: create a netdev notifier for DSA to reject PTP on DSA master

The fact that PTP 2-step TX timestamping is broken on DSA switches if
the master also timestamps the same packets is documented by c

net: create a netdev notifier for DSA to reject PTP on DSA master

The fact that PTP 2-step TX timestamping is broken on DSA switches if
the master also timestamps the same packets is documented by commit
f685e609a301 ("net: dsa: Deny PTP on master if switch supports it").
We attempt to help the users avoid shooting themselves in the foot by
making DSA reject the timestamping ioctls on an interface that is a DSA
master, and the switch tree beneath it contains switches which are aware
of PTP.

The only problem is that there isn't an established way of intercepting
ndo_eth_ioctl calls, so DSA creates avoidable burden upon the network
stack by creating a struct dsa_netdevice_ops with overlaid function
pointers that are manually checked from the relevant call sites. There
used to be 2 such dsa_netdevice_ops, but now, ndo_eth_ioctl is the only
one left.

There is an ongoing effort to migrate driver-visible hardware timestamping
control from the ndo_eth_ioctl() based API to a new ndo_hwtstamp_set()
model, but DSA actively prevents that migration, since dsa_master_ioctl()
is currently coded to manually call the master's legacy ndo_eth_ioctl(),
and so, whenever a network device driver would be converted to the new
API, DSA's restrictions would be circumvented, because any device could
be used as a DSA master.

The established way for unrelated modules to react on a net device event
is via netdevice notifiers. So we create a new notifier which gets
called whenever there is an attempt to change hardware timestamping
settings on a device.

Finally, there is another reason why a netdev notifier will be a good
idea, besides strictly DSA, and this has to do with PHY timestamping.

With ndo_eth_ioctl(), all MAC drivers must manually call
phy_has_hwtstamp() before deciding whether to act upon SIOCSHWTSTAMP,
otherwise they must pass this ioctl to the PHY driver via
phy_mii_ioctl().

With the new ndo_hwtstamp_set() API, it will be desirable to simply not
make any calls into the MAC device driver when timestamping should be
performed at the PHY level.

But there exist drivers, such as the lan966x switch, which need to
install packet traps for PTP regardless of whether they are the layer
that provides the hardware timestamps, or the PHY is. That would be
impossible to support with the new API.

The proposal there, too, is to introduce a netdev notifier which acts as
a better cue for switching drivers to add or remove PTP packet traps,
than ndo_hwtstamp_set(). The one introduced here "almost" works there as
well, except for the fact that packet traps should only be installed if
the PHY driver succeeded to enable hardware timestamping, whereas here,
we need to deny hardware timestamping on the DSA master before it
actually gets enabled. This is why this notifier is called "PRE_", and
the notifier that would get used for PHY timestamping and packet traps
would be called NETDEV_CHANGE_HWTSTAMP. This isn't a new concept, for
example NETDEV_CHANGEUPPER and NETDEV_PRECHANGEUPPER do the same thing.

In expectation of future netlink UAPI, we also pass a non-NULL extack
pointer to the netdev notifier, and we make DSA populate it with an
informative reason for the rejection. To avoid making it go to waste, we
make the ioctl-based dev_set_hwtstamp() create a fake extack and print
the message to the kernel log.

Link: https://lore.kernel.org/netdev/20230401191215.tvveoi3lkawgg6g4@skbuf/
Link: https://lore.kernel.org/netdev/20230310164451.ls7bbs6pdzs4m6pw@skbuf/
Signed-off-by: Vladimir Oltean <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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