This patch series provides a base and cleanup for the
upcoming EF10 SRIOV support.
This patch moves the VF state into siena_nic_data as a basis to
save the VF state based on nic type.
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
write_count and insert_count can wrap around, making > check invalid.
Fixes: 70b33fb0dd ("sfc: add support for
skb->xmit_more").
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Don't ring the doorbell, and don't do PIO. This will also prevent
TX Push, because there will be more than one buffer waiting when
the doorbell is rung.
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Conflicts:
arch/mips/net/bpf_jit.c
drivers/net/can/flexcan.c
Both the flexcan and MIPS bpf_jit conflicts were cases of simple
overlapping changes.
Signed-off-by: David S. Miller <davem@davemloft.net>
Reported by Nikolay Aleksandrov. In efx_init_port() we call
efx_mac_reconfigure() to work around a Falcon/A1 limitation, and this calls
efx_{arch}_filter_sync_rx_mode(), which takes the addr_list_lock; but this
lock is uninitialised, because we haven't called register_netdevice() yet.
So, in efx_farch_filter_sync_rx_mode(), check efx_dev_registered() before
doing anything else.
The EF10 equivalent, efx_ef10_filter_sync_rx_mode(), already has the
corresponding check.
Signed-off-by: Edward Cree <ecree@solarflare.com>
Tested-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Convert the normal transmit completion path from dev_kfree_skb_any()
to dev_consume_skb_any() to help keep dropped packet profiling
meaningful.
Signed-off-by: Rick Jones <rick.jones2@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
We should prefer `struct pci_device_id` over `DEFINE_PCI_DEVICE_TABLE` to
meet kernel coding style guidelines. This issue was reported by checkpatch.
A simplified version of the semantic patch that makes this change is as
follows (http://coccinelle.lip6.fr/):
// <smpl>
@@
identifier i;
declarer name DEFINE_PCI_DEVICE_TABLE;
initializer z;
@@
- DEFINE_PCI_DEVICE_TABLE(i)
+ const struct pci_device_id i[]
= z;
// </smpl>
[bhelgaas: add semantic patch]
Signed-off-by: Benoit Taine <benoit.taine@lip6.fr>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
__iowrite64_copy() isn't quite the same as efx_memcpy_64(), but
it looks close enough:
- The length is in units of qwords not bytes
- It never byte-swaps, but that doesn't make a difference now as PIO
is only enabled for x86_64
- It doesn't include any memory barriers, but that's OK as there is a
barrier just before pushing the doorbell
- mlx4_en uses it for the same purpose
Compile-tested only.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch adds the sfc driver code for implementing busy polling.
It adds ndo_busy_poll method and locking between it and napi poll.
It also adds each napi to the napi_hash right after netif_napi_add().
Uses efx_start_eventq and efx_stop_eventq in the self tests.
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Implement per channel software TX and RX packet counters
accessed as ethtool statistics.
This allows confirmation with MAC statistics.
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Added a counter rx_noskb_drop for failure to allocate an skb.
Summed the per-channel rx_nodesc_trunc counters earlier so that they can
be included in rx_dropped.
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Needed to select 40G mode on a 10G/40G capable card.
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Conflicts:
net/core/rtnetlink.c
net/core/skbuff.c
Both conflicts were very simple overlapping changes.
Signed-off-by: David S. Miller <davem@davemloft.net>
Fixes:ee45fd92c739
("sfc: Use TX PIO for sufficiently small packets")
The linux net driver uses memcpy_toio() in order to copy into
the PIO buffers.
Even on a 64bit machine this causes 32bit accesses to a write-
combined memory region.
There are hardware limitations that mean that only 64bit
naturally aligned accesses are safe in all cases.
Due to being write-combined memory region two 32bit accesses
may be coalesced to form a 64bit non 64bit aligned access.
Solution was to open-code the memory copy routines using pointers
and to only enable PIO for x86_64 machines.
Not tested on platforms other than x86_64 because this patch
disables the PIO feature on other platforms.
Compile-tested on x86 to ensure that works.
The WARN_ON_ONCE() code in the previous version of this patch
has been moved into the internal sfc debug driver as the
assertion was unnecessary in the upstream kernel code.
This bug fix applies to v3.13 and v3.14 stable branches.
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Ben Hutchings says:
====================
Pull request: Fixes for new ethtool RSS commands
This addresses several problems I previously identified with the new
ETHTOOL_{G,S}RSSH commands:
1. Missing validation of reserved parameters
2. Vague documentation
3. Use of unnamed magic number
4. No consolidation with existing driver operations
I don't currently have access to suitable network hardware, but have
tested these changes with a dummy driver that can support various
combinations of operations and sizes, together with (a) Debian's ethtool
3.13 (b) ethtool 3.14 with the submitted patch to use ETHTOOL_{G,S}RSSH
and minor adjustment for fixes 1 and 3.
v2: Update RSS operations in vmxnet3 too
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
ETHTOOL_{G,S}RXFHINDIR and ETHTOOL_{G,S}RSSH should work for drivers
regardless of whether they expose the hash key, unless you try to
set a hash key for a driver that doesn't expose it.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Conflicts:
drivers/net/bonding/bond_alb.c
drivers/net/ethernet/altera/altera_msgdma.c
drivers/net/ethernet/altera/altera_sgdma.c
net/ipv6/xfrm6_output.c
Several cases of overlapping changes.
The xfrm6_output.c has a bug fix which overlaps the renaming
of skb->local_df to skb->ignore_df.
In the Altera TSE driver cases, the register access cleanups
in net-next overlapped with bug fixes done in net.
Similarly a bug fix to send ALB packets in the bonding driver using
the right source address overlaps with cleanups in net-next.
Signed-off-by: David S. Miller <davem@davemloft.net>
o min_tx_rate puts lower limit on the VF bandwidth. VF is guaranteed
to have a bandwidth of at least this value.
max_tx_rate puts cap on the VF bandwidth. VF can have a bandwidth
of up to this value.
o A new handler set_vf_rate for attr IFLA_VF_RATE has been introduced
which takes 4 arguments:
netdev, VF number, min_tx_rate, max_tx_rate
o ndo_set_vf_rate replaces ndo_set_vf_tx_rate handler.
o Drivers that currently implement ndo_set_vf_tx_rate should now call
ndo_set_vf_rate instead and reject attempt to set a minimum bandwidth
greater than 0 for IFLA_VF_TX_RATE when IFLA_VF_RATE is not yet
implemented by driver.
o If user enters only one of either min_tx_rate or max_tx_rate, then,
userland should read back the other value from driver and set both
for IFLA_VF_RATE.
Drivers that have not yet implemented IFLA_VF_RATE should always
return min_tx_rate as 0 when read from ip tool.
o If both IFLA_VF_TX_RATE and IFLA_VF_RATE options are specified, then
IFLA_VF_RATE should override.
o Idea is to have consistent display of rate values to user.
o Usage example: -
./ip link set p4p1 vf 0 rate 900
./ip link show p4p1
32: p4p1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode
DEFAULT qlen 1000
link/ether 00:0e:1e:08:b0:f0 brd ff:ff:ff:ff:ff:ff
vf 0 MAC 3e:a0:ca:bd:ae:5a, tx rate 900 (Mbps), max_tx_rate 900Mbps
vf 1 MAC f6:c6:7c:3f:3d:6c
vf 2 MAC 56:32:43:98:d7:71
vf 3 MAC d6:be:c3:b5:85:ff
vf 4 MAC ee:a9:9a:1e:19:14
vf 5 MAC 4a:d0:4c:07:52:18
vf 6 MAC 3a:76:44:93:62:f9
vf 7 MAC 82:e9:e7:e3:15:1a
./ip link set p4p1 vf 0 max_tx_rate 300 min_tx_rate 200
./ip link show p4p1
32: p4p1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode
DEFAULT qlen 1000
link/ether 00:0e:1e:08:b0:f0 brd ff:ff:ff:ff:ff:ff
vf 0 MAC 3e:a0:ca:bd:ae:5a, tx rate 300 (Mbps), max_tx_rate 300Mbps,
min_tx_rate 200Mbps
vf 1 MAC f6:c6:7c:3f:3d:6c
vf 2 MAC 56:32:43:98:d7:71
vf 3 MAC d6:be:c3:b5:85:ff
vf 4 MAC ee:a9:9a:1e:19:14
vf 5 MAC 4a:d0:4c:07:52:18
vf 6 MAC 3a:76:44:93:62:f9
vf 7 MAC 82:e9:e7:e3:15:1a
./ip link set p4p1 vf 0 max_tx_rate 600 rate 300
./ip link show p4p1
32: p4p1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode
DEFAULT qlen 1000
link/ether 00:0e:1e:08:b0:f brd ff:ff:ff:ff:ff:ff
vf 0 MAC 3e:a0:ca:bd:ae:5, tx rate 600 (Mbps), max_tx_rate 600Mbps,
min_tx_rate 200Mbps
vf 1 MAC f6:c6:7c:3f:3d:6c
vf 2 MAC 56:32:43:98:d7:71
vf 3 MAC d6:be:c3:b5:85:ff
vf 4 MAC ee:a9:9a:1e:19:14
vf 5 MAC 4a:d0:4c:07:52:18
vf 6 MAC 3a:76:44:93:62:f9
vf 7 MAC 82:e9:e7:e3:15:1a
Signed-off-by: Sucheta Chakraborty <sucheta.chakraborty@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net: get rid of SET_ETHTOOL_OPS
Dave Miller mentioned he'd like to see SET_ETHTOOL_OPS gone.
This does that.
Mostly done via coccinelle script:
@@
struct ethtool_ops *ops;
struct net_device *dev;
@@
- SET_ETHTOOL_OPS(dev, ops);
+ dev->ethtool_ops = ops;
Compile tested only, but I'd seriously wonder if this broke anything.
Suggested-by: Dave Miller <davem@davemloft.net>
Signed-off-by: Wilfried Klaebe <w-lkml@lebenslange-mailadresse.de>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
If the sfc driver is in legacy interrupt mode (either explicitly by
using interrupt_mode module param or by falling back to it) it will
hit a warning at kernel/irq/manage.c because it will try to free an irq
which wasn't allocated by it in the first place because the MSI(X) irqs are
zero and it'll try to free them unconditionally. So fix it by checking if
we're in legacy mode and freeing the appropriate irqs.
CC: Zenghui Shi <zshi@redhat.com>
CC: Ben Hutchings <ben@decadent.org.uk>
CC: <linux-net-drivers@solarflare.com>
CC: Shradha Shah <sshah@solarflare.com>
CC: David S. Miller <davem@davemloft.net>
Fixes: 1899c111a5 ("sfc: Fix IRQ cleanup in case of a probe failure")
Reported-by: Zenghui Shi <zshi@redhat.com>
Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Acked-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
When an MCDI command times out (whether or not we find it
completed when we poll), call efx_mcdi_abandon(), which tells
all subsequent MCDI calls to fail-fast, and queues up an FLR.
Because an FLR doesn't lead to receiving any reboot even from
the MC (unlike most other types of reset), we have to call
efx_ef10_reset_mc_allocations.
In efx_start_all(), if a reset (of any kind) is pending, we
bail out.
Without this, attempts to reconfigure (e.g. change mtu) can
cause driver/mc state inconsistency if the first MCDI call
triggers an FLR.
For similar reasons, on EF10, in
efx_reset_down(method=RESET_TYPE_MCDI_TIMEOUT), set the number
of active queues to zero before calling efx_stop_all().
And, on farch, in efx_reset_up(method=RESET_TYPE_MCDI_TIMEOUT),
set active_queues and flushes pending & outstanding to zero.
efx_mcdi_mode_{poll,event}() should not take us out of fail-fast
mode. Instead, this is done by efx_mcdi_reset() after the FLR
completes.
The new FLR reset_type RESET_TYPE_MCDI_TIMEOUT doesn't really
fit into the hierarchy of reset 'scopes' whereby efx_reset()
decides some resets subsume others. Thus, it uses separate logic.
Also, fixed up some inconsistency around RESET_TYPE_MC_BIST,
which was in the wrong place in that hierarchy.
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
When using the "separate_tx_channels=1" module parameter, the TX queues are
initially numbered starting from the first TX-only channel number (after all the
RX-only channels). efx_set_channels() renumbers the queues so that they are
indexed from zero.
On EF10, the TX queues need to be relabelled in this way before calling the
dimension_resources NIC type operation, otherwise the TX queue PIO buffers can be
linked to the wrong VIs when using "separate_tx_channels=1".
Added comments to explain UC/WC mappings for PIO buffers
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch updates the many PTP Hardware Clock drivers with the
newly introduced field that advertises the number of programmable
pins. Some of these devices do have programmable pins, but the
implementation will have to wait for follow on patches.
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Processing any incoming packets with a with a napi budget of 0
is incorrect driver behavior.
This matters as netpoll will shortly call drivers with a budget of 0
to avoid receive packet processing happening in hard irq context.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Faster than memcpy/memset on some architectures.
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Conflicts:
drivers/net/wireless/ath/ath9k/recv.c
drivers/net/wireless/mwifiex/pcie.c
net/ipv6/sit.c
The SIT driver conflict consists of a bug fix being done by hand
in 'net' (missing u64_stats_init()) whilst in 'net-next' a helper
was created (netdev_alloc_pcpu_stats()) which takes care of this.
The two wireless conflicts were overlapping changes.
Signed-off-by: David S. Miller <davem@davemloft.net>
If we receive a PTP event from the NIC when we haven't set up PTP state
in the driver, we attempt to read through a NULL pointer efx->ptp_data,
triggering a panic.
Signed-off-by: Edward Cree <ecree@solarflare.com>
Acked-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
As result of deprecation of MSI-X/MSI enablement functions
pci_enable_msix() and pci_enable_msi_block() all drivers
using these two interfaces need to be updated to use the
new pci_enable_msi_range() and pci_enable_msix_range()
interfaces.
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Cc: Shradha Shah <sshah@solarflare.com>
Cc: linux-net-drivers@solarflare.com
Cc: netdev@vger.kernel.org
Cc: linux-pci@vger.kernel.org
Acked-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Remove trailing blank lines in several files.
Use only one blank line between functions.
Add a blank line as a separator in a few places.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
We don't use 'Solarstorm' or 'Solarflare Communications' in full
any more.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Functions such as is_valid_ether_addr() expect u8 *, so use that
instead of char *.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
We allocate efx_channel structures with kzalloc() so we don't need to
zero-initialise individual fields in efx_probe_channel(). Further,
this function will be called again during DMA ring resizing and we
should not reset any statistics then.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
EF10 implements option descriptors to switch TX checksum offload
on and off between packets. We could therefore use a single
hardware TX queue per kernel TX queue, although we don't yet.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
These DMA descriptor types will only be used by the userland
networking stack.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
If CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is defined then NET_IP_ALIGN
will be defined as 0, so this macro is redundant.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
There is substantial latency in generation and handling of PPS events
from the NIC, which we have to correct for before passing a host
timestamp to the PPS subsystem. We compare clocks with the MC,
giving us two offsets to subtract from the timestamp generated by
pps_get_ts():
(a) Time from the last good sync (where we got host and NIC timestamps
for nearly the same instant) to the time we called pps_get_ts()
(b) Time from NIC top of second to the last good sync
We currently calculate (a) + (b) in a quite confusing way.
Instead, calculate (a) completely, then add (b) to it.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Use conventional net_ratelimit() instead.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Commit ee45fd92c7 ("sfc: Use TX PIO
for sufficiently small packets") introduced the following warning:
drivers/net/ethernet/sfc/tx.c: In function 'efx_enqueue_skb':
drivers/net/ethernet/sfc/tx.c:432:1: warning: label 'finish_packet' defined but not used
Stick the label inside the same #ifdef that the code which calls
it uses. Note that this is only seen for arch that do not set
ARCH_HAS_IOREMAP_WC, such as arm, mips, sparc, ..., as the others
enable the write combining code and hence use the label.
Cc: Jon Cooper <jcooper@solarflare.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
As part of a workaround for a hardware erratum in the SFC9100 family
(SF bug 35388), the TX_DESC_UPD_DWORD register address is also used
for communicating with the event block, and only descriptor pointer
values < 2048 are valid.
If the TX DMA ring size is increased to 4096 descriptors (which the
firmware still allows) then we may write a descriptor pointer
value >= 2048, which has entirely different and undesirable effects!
Limit the TX DMA ring size correctly when this workaround is in
effect.
Fixes: 8127d661e7 ('sfc: Add support for Solarflare SFC9100 family')
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Somehow I transposed these two while bringing the original statistics
support upstream.
Fixes: 99691c4ac1 ('sfc: Add PTP counters to ethtool stats')
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
PORT_RESET MC command was NOP in the ef10 firmware hence we are using
ENTITY_RESET to make sure all resource allocations are reset.
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fixes the following sparse warning:
drivers/net/ethernet/sfc/falcon.c:2601:6: warning:
symbol 'falcon_pull_nic_stats' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Drivers should call skb_set_hash to set the hash and its type
in an skbuff.
Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Ben Hutchings says:
====================
Miscellaneous changes for 3.14:
1. Add more information to some WARN messages.
2. Refactor pushing of RSS configuration, from Andrew Rybchenko.
3. Refactor handling of automatic (device address list) vs manual (RX
NFC) MAC filters.
4. Implement clearing of manual RX filters on EF10 when ntuple offload
is disabled.
5. Remove definitions that are unused since the RX buffer allocation
changes, from Andrew Rybchenko.
6. Improve naming of some statistics, from Shradha Shah.
7. Add statistics for PTP support code.
8. Fix insertion of RX drop filters on EF10.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
When we insert an filter, the firmware checks that the given RX queue
index is in range even if it will not be used. In case we're
inserting a drop filter, pass the value 0.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
