selftests: net: devlink_port_split.py: skip test if no suitable device available

The `devlink -j port show` command output may not contain the "flavour"
key, an example from Ubuntu 22.10 s390x LPAR(5.19.0-37-generic), with
mlx4 driver and iproute2-5.15.0:
{"port":{"pci/0001:00:00.0/1":{"type":"eth","netdev":"ens301"},
"pci/0001:00:00.0/2":{"type":"eth","netdev":"ens301d1"},
"pci/0002:00:00.0/1":{"type":"eth","netdev":"ens317"},
"pci/0002:00:00.0/2":{"type":"eth","netdev":"ens317d1"}}}

This will cause a KeyError exception.

Create a validate_devlink_output() to check for this "flavour" from
devlink command output to avoid this KeyError exception. Also let
it handle the check for `devlink -j dev show` output in main().

Apart from this, if the test was not started because the max lanes of
the designated device is 0. The script will still return 0 and thus
causing a false-negative test result.

Use a found_max_lanes flag to determine if these tests were skipped
due to this reason and return KSFT_SKIP to make it more clear.

Link: https://bugs.launchpad.net/bugs/1937133
Fixes: f3348a82e727 ("selftests: net: Add port split test")
Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Link: https://lore.kernel.org/r/20230315165353.229590-1-po-hsu.lin@canonical.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

selftests: net: devlink_port_split: check devlink returned an element before dereferencing it

And thus avoid a Python stacktrace:

~/linux/tools/testing/selftests/net$ ./devlink_port_split.py
Traceback (most recent call last):
File "/home/linux/tools/testing/selftests/net/./devlink_port_split.py",
line 277, in <module> main()
File "/home/linux/tools/testing/selftests/net/./devlink_port_split.py",
line 242, in main
dev = list(devs.keys())[0]
IndexError: list index out of range

Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

selftests: net: devlink_port_split.py: skip the test if no devlink device

When there is no devlink device, the following command will return:
$ devlink -j dev show
{dev:{}}

This will cause IndexError when trying to access the first element
in dev of this json dataset. Use the kselftest framework skip code
to skip this test in this case.

Example output with this change:
# selftests: net: devlink_port_split.py
# no devlink device was found, test skipped
ok 7 selftests: net: devlink_port_split.py # SKIP

Link: https://bugs.launchpad.net/bugs/1928889
Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tweewide: Fix most Shebang lines

Change every shebang which does not need an argument to use /usr/bin/env.
This is needed as not every distro has everything under /usr/bin,
sometimes not even bash.

Signed-off-by: Finn Behrens <me@kloenk.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

selftests: net: Add port split test

Test port split configuration using previously added number of port lanes
attribute.

Check that all the splittable ports are successfully split to their maximum
number of lanes and below, and that those which are not splittable fail to
be split.

Test output example:

TEST: swp4 is unsplittable [ OK ]
TEST: split port swp53 into 4 [ OK ]
TEST: Unsplit port pci/0000:03:00.0/25 [ OK ]
TEST: split port swp53 into 2 [ OK ]
TEST: Unsplit port pci/0000:03:00.0/25 [ OK ]

Signed-off-by: Danielle Ratson <danieller@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>