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In a future patch, the port I/O functions (`inb()`, `outb()`, and
friends will only be declared in the `HAS_IOPORT` configuration option
is enabled.

The ni_labpc_common module is used by the ni_labpc module (for ISA
cards), the ni_labpc_cs module (for PCMCIA cards), and the ni_labpc_pci
module (for PCI cards).  The ISA and PCMCIA cards use port I/O and the
PCI cards use memory-mapped I/O.

Conditionally compile the parts of the module that use the port I/O
functions so they are compiled if and only if the `CONFIG_HAS_IOPORT`
macro is defined, so that the module can be built if the port I/O
functions have not been declared.

Add a run-time check in the `labpc_common_attach()` to return an error
if the comedi device wants to use port I/O when the `CONFIG_HAS_IOPORT`
macro is undefined.

The changes allow the module to be built even if the port I/O functions
have not been declared.

Cc: Arnd Bergmann <arnd@kernel.org>
Cc: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20230913170712.111719-9-abbotti@mev.co.uk

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>