packing() is now used in some hot paths, and it would be good to get rid
of some ifs and buts that depend on "op", to speed things up a little bit.

With the main implementations now taking size_t endbit, we no longer
have to check for negative values. Update the local integer variables to
also be size_t to match.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20241002-packing-kunit-tests-and-split-pack-unpack-v2-5-8373e551eae3@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Geert Uytterhoeven described packing() as "really bad API" because of
not being able to enforce const correctness. The same function is used
both when "pbuf" is input and "uval" is output, as in the other way
around.

Create 2 wrapper functions where const correctness can be ensured.
Do ugly type casts inside, to be able to reuse packing() as currently
implemented - which will _not_ modify the input argument.

Also, take the opportunity to change the type of startbit and endbit to
size_t - an unsigned type - in these new function prototypes. When int,
an extra check for negative values is necessary. Hopefully, when
packing() goes away completely, that check can be dropped.

My concern is that code which does rely on the conditional directionality
of packing() is harder to refactor without blowing up in size. So it may
take a while to completely eliminate packing(). But let's make alternatives
available for those who do not need that.

Link: https://lore.kernel.org/netdev/20210223112003.2223332-1-geert+renesas@glider.be/
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20241002-packing-kunit-tests-and-split-pack-unpack-v2-4-8373e551eae3@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

It is not necessary to have the kernel-doc duplicated both in the
header and in the implementation. It is better to have it near the
implementation of the function, since in C, a function can have N
declarations, but only one definition.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20241002-packing-kunit-tests-and-split-pack-unpack-v2-3-8373e551eae3@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

NXP Legal insists that the following are not fine:

- Saying "NXP Semiconductors" instead of "NXP", since the company's
  registered name is "NXP"

- Putting a "(c)" sign in the copyright string

- Putting a comma in the copyright string

The only accepted copyright string format is "Copyright <year-range> NXP".

This patch changes the copyright headers in the networking files that
were sent by me, or derived from code sent by me.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This provides an unified API for accessing register bit fields
regardless of memory layout. The basic unit of data for these API
functions is the u64. The process of transforming an u64 from native CPU
encoding into the peripheral's encoding is called 'pack', and
transforming it from peripheral to native CPU encoding is 'unpack'.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>