comedi: ni_mio_common: Conditionally use I/O port or MMIO

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_mio_common.c" file contains calls to both port I/O functions and
memory-mapped I/O functions. The file is `#include`d by "ni_atmio.c",
"ni_mio_cs.c", and "ni_pcimio.c" for the ni_atmio, ni_mio_cs, and
ni_pcimio modules, respectively. Only "ni_pcimio.c" defines the
`PCIDMA` macro before including "ni_mio_common.c" and various bits of
code in "ni_mio_common.c" is conditionally compiled according to whether
that macro is defined or not. Currently, the port I/O function calls
are compiled in regardless of whether the `PCIDMA` macro is defined or
not. However, the fact is that the ni_atmio and ni_mio_cs modules will
never call the memory-mapped I/O functions, and the ni_pcimio module
will never call the port I/O functions.

Calls to the port I/O and memory-mapped I/O functions is confined to the
`ni_writel()`, `ni_writew()`, `ni_writeb()`, `ni_readl()`, `ni_readw()`,
and `ni_readb()` functions which do a run-time test to decide whether to
call the port I/O functions or the memory-mapped I/O functions.
Conditionally compile two variants of the functions so they only call
the port I/O functions if the `PCIDMA` macro is undefined (for the
ni_atmio and ni_mio_cs modules), and only call the memory-mapped I/O
functions if the `PCIDMA` macro is defined (for the ni_pcimio module).

Add a run-time check in the `ni_E_init()` function to return an error if
the comedi device has been set up to use port I/O if `PCIDMA` is
defined, or has been set up to use memory-mapped I/O if `PCIDMA` is not
defined.

The changes make it possible to build the ni_pcimio module even if the
port I/O functions have not been declared. (The ni_atmio and ni_mio_cs
modules do still require the port I/O functions to be 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/20230913170712.111719-10-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

comedi: comedi_8255: Rework subdevice initialization functions

Comedi drivers can initialize an 8255 subdevice in I/O space by calling
`subdev_8255_init()`, or in memory-mapped I/O space by calling
`subdev_8255_mm_init()`, or by supplying a call-back function pointer
and context to either of those functions. Change it so that a new
function `subdev_8255_cb_init()` shall be called instead when supplying
a callback function and context, and remove the call-back function
parameter from `subdev_8255_init()` and `subdev_8255_mm_init()`.

Also rename `subdev_8255_init()` to `subdev_8255_io_init()`. The
parameters are changing, so might as well rename it at the same time.

Also rename the `regbase` member of `struct subdev_8255_private` to
`context` since this holds the context for the call-back function call.

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/20230913170712.111719-7-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

comedi: Move and rename "8255.h" to <linux/comedi/comedi_8255.h>

Some of the header files in "drivers/comedi/drivers/" are common enough
to be useful to out-of-tree comedi driver modules. Using them for
out-of-tree module builds is hampered by the headers being outside the
"include/" directory so it is desirable to move them.

There are about a couple of dozen Comedi device drivers that use the
"comedi_8255" module to add digital I/O subdevices based on the
venerable 8255 Programmable Peripheral Interface chip. The macros and
declarations to use that module are in the "8255.h" header file in the
comedi "drivers" directory. Move it into "include/linux/comedi/" and
rename it to "comedi_8255.h" for naming consistency reasons.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20211117120604.117740-4-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

staging: comedi: move out of staging directory

The comedi code came into the kernel back in 2008, but traces its
lifetime to much much earlier. It's been polished and buffed and
there's really nothing preventing it from being part of the "real"
portion of the kernel.

So move it to drivers/comedi/ as it belongs there.

Many thanks to the hundreds of developers who did the work to make this
happen.

Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: H Hartley Sweeten <hsweeten@visionengravers.com>
Link: https://lore.kernel.org/r/YHauop4u3sP6lz8j@kroah.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>