Measurements of the MDIO bus have shown that driving the MDIO bus
using interrupts is slow. Back to back MDIO transactions take about
90us, with 25us spent performing the transaction, and the remainder of
the time the bus is idle.
Replacing the completion interrupt with polled IO results in back to
back transactions of 40us. The polling loop waiting for the hardware
to complete the transaction takes around 28us. Which suggests
interrupt handling has an overhead of 50us, and polled IO nearly
halves this overhead, and doubles the MDIO performance.
Care has to be taken when setting the MII_SPEED register, or it can
trigger an MII event> That then upsets the polling, due to an
unexpected pending event.
Suggested-by: Chris Heally <cphealy@gmail.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Karsten Graul says:
====================
net/smc: extent buffer mapping and port handling
Add functionality to map/unmap and register/unregister memory buffers for
specific SMC-R links and for the whole link group. Prepare LLC layer messages
for the support of multiple links and extent the processing of adapter events.
And add further small preparations needed for the SMC-R failover support.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch is to add tc flower offload for the enetc IEEE 802.1Qci(PSFP)
function. There are four main feature parts to implement the flow
policing and filtering for ingress flow with IEEE 802.1Qci features.
They are stream identify(this is defined in the P802.1cb exactly but
needed for 802.1Qci), stream filtering, stream gate and flow metering.
Each function block includes many entries by index to assign parameters.
So for one frame would be filtered by stream identify first, then
flow into stream filter block by the same handle between stream identify
and stream filtering. Then flow into stream gate control which assigned
by the stream filtering entry. And then policing by the gate and limited
by the max sdu in the filter block(optional). At last, policing by the
flow metering block, index choosing at the fitering block.
So you can see that each entry of block may link to many upper entries
since they can be assigned same index means more streams want to share
the same feature in the stream filtering or stream gate or flow
metering.
To implement such features, each stream filtered by source/destination
mac address, some stream maybe also plus the vlan id value would be
treated as one flow chain. This would be identified by the chain_index
which already in the tc filter concept. Driver would maintain this chain
and also with gate modules. The stream filter entry create by the gate
index and flow meter(optional) entry id and also one priority value.
Offloading only transfer the gate action and flow filtering parameters.
Driver would create (or search same gate id and flow meter id and
priority) one stream filter entry to set to the hardware. So stream
filtering do not need transfer by the action offloading.
This architecture is same with tc filter and actions relationship. tc
filter maintain the list for each flow feature by keys. And actions
maintain by the action list.
Below showing a example commands by tc:
> tc qdisc add dev eth0 ingress
> ip link set eth0 address 10:00:80:00:00:00
> tc filter add dev eth0 parent ffff: protocol ip chain 11 \
flower skip_sw dst_mac 10:00:80:00:00:00 \
action gate index 10 \
sched-entry open 200000000 1 8000000 \
sched-entry close 100000000 -1 -1
Command means to set the dst_mac 10:00:80:00:00:00 to index 11 of stream
identify module. Then setting the gate index 10 of stream gate module.
Keep the gate open for 200ms and limit the traffic volume to 8MB in this
sched-entry. Then direct the frames to the ingress queue 1.
Signed-off-by: Po Liu <Po.Liu@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch is to let ethtool enable/disable the tc flower offload
features. Hardware ENETC has the feature of PSFP which is for per-stream
policing. When enable the tc hw offloading feature, driver would enable
the IEEE 802.1Qci feature. It is only set the register enable bit for
this feature not enable for any entry of per stream filtering and stream
gate or stream identify but get how much capabilities for each feature.
Signed-off-by: Po Liu <Po.Liu@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fix to return negative error code -ENOMEM from the error handling
case instead of 0, as done elsewhere in this function.
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This reverts commit 29ae6bd1b0.
The commit breaks ethernet function on i.MX6SX, i.MX7D, i.MX8MM,
i.MX8MQ, and i.MX8QXP platforms. Boot yocto system by NFS mounting
rootfs will be failed with the commit.
Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fixes coccicheck warning:
./drivers/net/ethernet/freescale/dpaa/dpaa_eth.c:2110:30-31:
WARNING comparing pointer to 0
Avoid pointer type value compared to 0.
Signed-off-by: Aishwarya Ramakrishnan <aishwaryarj100@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The change to polled IO for MDIO completion assumes that MII events
are only generated for MDIO transactions. However on some SoCs writing
to the MII_SPEED register can also trigger an MII event. As a result,
the next MDIO read has a pending MII event, and immediately reads the
data registers before it contains useful data. When the read does
complete, another MII event is posted, which results in the next read
also going wrong, and the cycle continues.
By writing 0 to the MII_DATA register before writing to the speed
register, this MII event for the MII_SPEED is suppressed, and polled
IO works as expected.
Fixes: 29ae6bd1b0 ("net: ethernet: fec: Replace interrupt driven MDIO with polled IO")
Reported-by: Andy Duan <fugang.duan@nxp.com>
Suggested-by: Andy Duan <fugang.duan@nxp.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
When building arm32 allmodconfig:
ERROR: modpost: "__aeabi_uldivmod"
[drivers/net/ethernet/freescale/dpaa2/fsl-dpaa2-eth.ko] undefined!
frames and cdan are both of type __u64 (unsigned long long) so we need
to use div64_u64 to avoid this issues.
Fixes: 460fd830dd ("dpaa2-eth: add channel stat to debugfs")
Link: https://github.com/ClangBuiltLinux/linux/issues/1012
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reported-by: kernelci.org bot <bot@kernelci.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Compute the average number of frames processed for each CDAN (Channel
Data Availability Notification) and export it to debugfs detailed
channel stats.
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Drivers ndo_setup_tc call should return -EOPNOTSUPP, when it cannot
support the qdisc type. Other return values will result in failing the
qdisc setup. This lead to qdisc noop getting assigned, which will
drop all TX packets on the interface.
Fixes: ab1e6de2bd ("dpaa2-eth: Add mqprio support")
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Take advantage of the bulk enqueue feature in .ndo_xdp_xmit.
We cannot use the XDP_XMIT_FLUSH since the architecture is not capable
to store all the frames dequeued in a NAPI cycle so we instead are
enqueueing all the frames received in a ndo_xdp_xmit call right away.
After setting up all FDs for the xdp_frames received, enqueue multiple
frames at a time until all are sent or the maximum number of retries is
hit.
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Instead of having a function that both creates a frame descriptor from
an xdp_frame and enqueues it, split this into two stages.
Add the dpaa2_eth_xdp_create_fd that just transforms an xdp_frame into a
FD while the actual enqueue callback is called directly from the ndo for
each frame.
This is particulary useful in conjunction with bulk enqueue.
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Update the dpaa2-eth driver to use the bulk enqueue function introduced
with the change to QBMAN ring mode. At the moment, no functional changes
are made but rather the driver just transitions to the new interface
while still enqueuing just one frame at a time.
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The enqueue dpaa2-eth callback now returns the number of successfully
enqueued frames. This is a preliminary patch necessary for adding
support for bulk ring mode enqueue.
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
An MDIO transaction normally starts with 32 1s as a preamble. However
not all devices requires such a preamble. Add a device tree property
which allows the preamble to be suppressed. This will half the size of
the MDIO transaction, allowing faster transactions. But it should only
be used when all devices on the bus support suppressed preamble.
Suggested-by: Chris Healy <Chris.Healy@zii.aero>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
MDIO busses typically operate at 2.5MHz. However many devices can
operate at faster speeds. This then allows more MDIO transactions per
second, useful for Ethernet switch statistics, or Ethernet PHY TDR
data. Allow the bus speed to be configured, using the standard
"clock-frequency" property, which i2c busses use to indicate the bus
speed. Before using this property, ensure all devices on the bus do
actually support the requested clock speed.
Suggested-by: Chris Healy <Chris.Healy@zii.aero>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Measurements of the MDIO bus have shown that driving the MDIO bus
using interrupts is slow. Back to back MDIO transactions take about
90us, with 25us spent performing the transaction, and the remainder of
the time the bus is idle.
Replacing the completion interrupt with polled IO results in back to
back transactions of 40us. The polling loop waiting for the hardware
to complete the transaction takes around 28us. Which suggests
interrupt handling has an overhead of 50us, and polled IO nearly
halves this overhead, and doubles the MDIO performance.
Suggested-by: Chris Heally <cphealy@gmail.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Each ENETC station interface (SI) has a VLAN filter list and a port
flag (PSIPVMR) by which it can be put in "VLAN promiscuous" mode, which
enables the reception of VLAN-tagged traffic even if it is not in the
VLAN filtering list.
Currently the handling of this setting works like this: the port starts
off as VLAN promiscuous, then it switches to enabling VLAN filtering as
soon as the first VLAN is installed in its filter via
.ndo_vlan_rx_add_vid. In practice that does not work out very well,
because more often than not, the first VLAN to be installed is out of
the control of the user: the 8021q module, if loaded, adds its rule for
802.1p (VID 0) traffic upon bringing the interface up.
What the user is currently seeing in ethtool is this:
ethtool -k eno2
rx-vlan-filter: on [fixed]
which doesn't match the intention of the code, but the practical reality
of having the 8021q module install its VID which has the side-effect of
turning on VLAN filtering in this driver. All in all, a slightly
confusing experience.
So instead of letting this driver switch the VLAN filtering state by
itself, just wire it up with the rx-vlan-filter feature from ethtool,
and let it be user-configurable just through that knob, except for one
case, see below.
In promiscuous mode, it is more intuitive that all traffic is received,
including VLAN tagged traffic. It appears that it is necessary to set
the flag in PSIPVMR for that to be the case, so VLAN promiscuous mode is
also temporarily enabled. On exit from promiscuous mode, the setting
made by ethtool is restored.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
On some SoCs, such as the i.MX6, it is necessary to set a bit
in the SoC level GPR register before suspending for wake on lan
to work.
The fec platform callback sleep_mode_enable was intended to allow this
but the platform implementation was NAK'd back in 2015 [1]
This means that, currently, wake on lan is broken on mainline for
the i.MX6 at least.
So implement the required bit setting in the fec driver by itself
by adding a new optional DT property indicating the GPR register
and adding the offset and bit information to the driver.
[1] https://www.spinics.net/lists/netdev/msg310922.html
Signed-off-by: Martin Fuzzey <martin.fuzzey@flowbird.group>
Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fix sparse warning:
drivers/net/ethernet/freescale/dpaa/dpaa_eth.c:2065:5:
warning: symbol 'dpaa_a050385_wa' was not declared. Should it be static?
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Overlapping header include additions in macsec.c
A bug fix in 'net' overlapping with the removal of 'version'
string in ena_netdev.c
Overlapping test additions in selftests Makefile
Overlapping PCI ID table adjustments in iwlwifi driver.
Signed-off-by: David S. Miller <davem@davemloft.net>
commit ed0a72e0de ("net/freescale: Clean drivers from static versions")
leave behind this, remove it .
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Treat all internal delay variants the same as RGMII.
Signed-off-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Set ethtool_ops->supported_coalesce_params to let
the core reject unsupported coalescing parameters.
This driver did not previously reject unsupported parameters.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Set ethtool_ops->supported_coalesce_params to let
the core reject unsupported coalescing parameters.
This driver did not previously reject unsupported parameters.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Set ethtool_ops->supported_coalesce_params to let
the core reject unsupported coalescing parameters.
This driver did not previously reject unsupported parameters
(other than adaptive rx, which will now be rejected by core).
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
fec_enet_set_coalesce() validates the previously set params
and if they are within range proceeds to apply the new ones.
The new ones, however, are not validated. This seems backwards,
probably a copy-paste error?
Compile tested only.
Fixes: d851b47b22 ("net: fec: add interrupt coalescence feature support")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Clang warns:
drivers/net/ethernet/freescale/dpaa/dpaa_eth.c:2860:9: warning:
converting the result of '?:' with integer constants to a boolean always
evaluates to 'true' [-Wtautological-constant-compare]
return DPAA_FD_DATA_ALIGNMENT ? ALIGN(headroom,
^
drivers/net/ethernet/freescale/dpaa/dpaa_eth.c:131:34: note: expanded
from macro 'DPAA_FD_DATA_ALIGNMENT'
\#define DPAA_FD_DATA_ALIGNMENT (fman_has_errata_a050385() ? 64 : 16)
^
1 warning generated.
This was exposed by commit 3c68b8fffb ("dpaa_eth: FMan erratum A050385
workaround") even though it appears to have been an issue since the
introductory commit 9ad1a37493 ("dpaa_eth: add support for DPAA
Ethernet") since DPAA_FD_DATA_ALIGNMENT has never been able to be zero.
Just replace the whole boolean expression with the true branch, as it is
always been true.
Link: https://github.com/ClangBuiltLinux/linux/issues/928
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Hardware timestamping support (PTP) on Rx requires extended
buffer descriptors, double the size of normal Rx descriptors.
On the current controller revision only the timestamping offload
requires extended Rx descriptors.
Since Rx timestamping can be turned on/off at runtime, make Rx ring
allocation configurable at runtime too. As a result, the static
config option FSL_ENETC_HW_TIMESTAMPING can be dropped and the
extended descriptors can be used only when Rx timestamping gets
activated.
The extension has the same size as the base descriptor, making
the descriptor iterators easy to update for the extended case.
Signed-off-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Improve maintainability of the code iterating the Rx buffer
descriptors to prepare it to support iterating extended Rx BD
descriptors as well.
Don't increment by one the h/w descriptor pointers explicitly,
provide an iterator that takes care of the h/w details.
Signed-off-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Refactor the stats len computation code to make it easier
to add new stats counters.
Signed-off-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The existence of the DT port node is the first thing checked
at probe time, and probing won't reach this point if the node
is missing.
Signed-off-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
If there is no valid MAC address in the device tree, use a random
MAC address.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Allow the initialization of the MAC to be performed even if the
device tree does not provide a valid MAC address. Later a random
MAC address should be assigned by the Ethernet driver.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Reuse the set_mac_address() in the init() function.
Signed-off-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Align buffers, data start, SG fragment length to avoid DMA splits.
These changes prevent the A050385 erratum to manifest itself:
FMAN DMA read or writes under heavy traffic load may cause FMAN
internal resource leak; thus stopping further packet processing.
The FMAN internal queue can overflow when FMAN splits single
read or write transactions into multiple smaller transactions
such that more than 17 AXI transactions are in flight from FMAN
to interconnect. When the FMAN internal queue overflows, it can
stall further packet processing. The issue can occur with any one
of the following three conditions:
1. FMAN AXI transaction crosses 4K address boundary (Errata
A010022)
2. FMAN DMA address for an AXI transaction is not 16 byte
aligned, i.e. the last 4 bits of an address are non-zero
3. Scatter Gather (SG) frames have more than one SG buffer in
the SG list and any one of the buffers, except the last
buffer in the SG list has data size that is not a multiple
of 16 bytes, i.e., other than 16, 32, 48, 64, etc.
With any one of the above three conditions present, there is
likelihood of stalled FMAN packet processing, especially under
stress with multiple ports injecting line-rate traffic.
To avoid situations that stall FMAN packet processing, all of the
above three conditions must be avoided; therefore, configure the
system with the following rules:
1. Frame buffers must not span a 4KB address boundary, unless
the frame start address is 256 byte aligned
2. All FMAN DMA start addresses (for example, BMAN buffer
address, FD[address] + FD[offset]) are 16B aligned
3. SG table and buffer addresses are 16B aligned and the size
of SG buffers are multiple of 16 bytes, except for the last
SG buffer that can be of any size.
Additional workaround notes:
- Address alignment of 64 bytes is recommended for maximally
efficient system bus transactions (although 16 byte alignment is
sufficient to avoid the stall condition)
- To support frame sizes that are larger than 4K bytes, there are
two options:
1. Large single buffer frames that span a 4KB page boundary can
be converted into SG frames to avoid transaction splits at
the 4KB boundary,
2. Align the large single buffer to 256B address boundaries,
ensure that the frame address plus offset is 256B aligned.
- If software generated SG frames have buffers that are unaligned
and with random non-multiple of 16 byte lengths, before
transmitting such frames via FMAN, frames will need to be copied
into a new single buffer or multiple buffer SG frame that is
compliant with the three rules listed above.
Signed-off-by: Madalin Bucur <madalin.bucur@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Core already zeroes out the struct ethtool_coalesce structure,
drivers don't have to set every field to 0 individually.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Rely on ethtool to properly present the fact that FW and bus
are not available for the gianfar driver.
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Rely on ethtool to properly present the fact that FW is not
available for the ucc_geth driver.
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Rely on ethtool to properly present the fact that FW is not
available for the dpaa driver.
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
There is no need to set static versions because linux kernel is
released all together with same version applicable to the whole
code base.
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Convert the DPAA2 ethernet driver to use the finalised link parameters
in mac_link_up() rather than the parameters in mac_config(), which are
more suited to the needs of the DPAA2 MC firmware than those available
via mac_config().
Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Propagate the resolved link parameters via the mac_link_up() call for
MACs that do not automatically track their PCS state. We propagate the
link parameters via function arguments so that inappropriate members
of struct phylink_link_state can't be accessed, and creating a new
structure just for this adds needless complexity to the API.
Tested-by: Andre Przywara <andre.przywara@arm.com>
Tested-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add support for ethtool -r so that PHY negotiation can be restarted.
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Andrew Lunn