Merge branch 'implement-DEVLINK_CMD_REGION_NEW'

Merge branch 'implement-DEVLINK_CMD_REGION_NEW'

Jacob Keller says:

====================
implement DEVLINK_CMD_REGION_NEW

This series adds support for the DEVLINK_CMD_REGION_NEW operation, used to
enable userspace requesting a snapshot of a region on demand.

This can be useful to enable adding regions for a driver for which there is
no trigger to create snapshots. By making this a core part of devlink, there
is no need for the drivers to use a separate channel such as debugfs.

The primary intent for this kind of region is to expose device information
that might be useful for diagnostics and information gathering.

The first few patches refactor regions to support a new ops structure for
extending the available operations that regions can perform. This includes
converting the destructor into an op from a function argument.

Next, patches refactor the snapshot id allocation to use an xarray which
tracks the number of current snapshots using a given id. This is done so
that id lifetime can be determined, and ids can be released when no longer
in use.

Without this change, snapshot ids remain used forever, until the snapshot_id
count rolled over UINT_MAX.

Finally, code to enable the previously unused DEVLINK_CMD_REGION_NEW is
added. This code enforces that the snapshot id is always provided, unlike
previous revisions of this series.

Finally, a patch is added to enable using this new command via the .snapshot
callback in both netdevsim and the ice driver.

For the ice driver, a new "nvm-flash" region is added, which will enable
read access to the NVM flash contents. The intention for this is to allow
diagnostics tools to gather information about the device. By using a
snapshot and gathering the NVM contents all at once, the contents can be
atomic.

Links to previous discussions:
1st RFC - https://lore.kernel.org/netdev/20200130225913.1671982-1-jacob.e.keller@intel.com/
2nd RFC - https://lore.kernel.org/netdev/20200214232223.3442651-1-jacob.e.keller@intel.com/
v1 - https://lore.kernel.org/netdev/20200324223445.2077900-1-jacob.e.keller@intel.com/
v2 - https://lore.kernel.org/netdev/20200326035157.2211090-1-jacob.e.keller@intel.com/

Major changes since RFC:
* use an xarray for tracking snapshot ids, rather than an IDR
* remove support for auto-generated snapshot ids in DEVLINK_CMD_REGION_NEW

See each patch for an individual changelog per-patch
====================

Signed-off-by: David S. Miller <davem@davemloft.net>