re: mlxsw: spectrum: Adjust headroom buffers for 8x ports

[Colin Ian King <colin.king@canonical.com>]

Hi

Static analysis with Coverity has detected an issue that relies on the
machine endianness to work. The commit in question is:

commit 60833d54d56c21e7538296eb2e00e104768fd047
Author: Ido Schimmel <idosch@mellanox.com>
Date:   Tue Jun 16 10:14:58 2020 +0300

    mlxsw: spectrum: Adjust headroom buffers for 8x ports

in line:
    mlxsw_sp_port_headroom_8x_adjust(mlxsw_sp_port, (u16 *) &buffsize);


The cast of the u32 buffsize to (u16 *) to scale buffsize in the call to
to mlxsw_sp_port_headroom_8x_adjust() will behave differently on big
endian architectures to that of little endian architectures.  I'm not
sure if this is intentional or not.

One solution is to either make buffsize a u16, but I am concerned this
may be incorrect as the buffsize is assigned from the call
mlxsw_sp_span_buffsize_get() and this returns a u32 so we may have
overflow issues. Probably better to make
mlxsw_sp_port_headroom_8x_adjust handle u32 integers and to return the
adjusted value rather than modifying it by pass-by-reference.

Colin