Merge branch 'mlxsw-introduce-modular-system-support-by-minimal-driver'

Merge branch 'mlxsw-introduce-modular-system-support-by-minimal-driver'

Petr Machata says:

====================
mlxsw: Introduce modular system support by minimal driver

Vadim Pasternak writes:

This patchset adds line cards support in mlxsw_minimal, which is used
for monitoring purposes on BMC systems. The BMC is connected to the
ASIC over I2C bus, unlike the host CPU that is connected to the ASIC
via PCI bus.

The BMC system needs to be notified whenever line cards become active
or inactive, so that, for example, netdevs will be registered /
unregistered by mlxsw_minimal. However, traps cannot be generated
towards the BMC over the I2C bus. To overcome that, the I2C bus driver
(i.e., mlxsw_i2c) registers an handler for an IRQ that is fired upon
specific system wide changes, like line card activation and
deactivation.

The generated event is handled by mlxsw_core, which checks whether
anything changed in the state of available line cards. If a line card
becomes active or inactive, interested parties such as mlxsw_minimal
are notified via their registered line card event callback.

Patch set overview:

Patches #1 is preparations.

Patches #2-#3 extend mlxsw_core with an infrastructure to handle the
	previously mentioned system events.

Patch #4 extends the I2C bus driver to register an handler for the IRQ
	fired upon specific system wide changes.

Patches #5-#8 gradually add line cards support in mlxsw_minimal by
	dynamically registering / unregistering netdevs for ports found on
	line cards, whenever a line card becomes active / inactive.
====================

Link: https://lore.kernel.org/r/cover.1661093502.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>