comedi: Add new driver for ADLink PCI-7250 series

The ADLink PCI-7250, LPCI-7250, and LPCIe-7250 are PCI/PCIe boards with
8 relay outputs and 8 isolated digital inputs.  Add a new Comedi driver
"adl_pci7250" to support them.

It is possible to add up to three PCI-7251 plug-in modules to the
PCI-7250, with 8 relay outputs and 8 isolated digital inputs per plug-in
module.  We cannot reliably detect whether the modules are fitted
without changing their state.  It is harmless to assume the modules are
fitted; they just won't do anything, so the driver allows all 32 relay
outputs to be written (and their initial state to be read), and all 32
digital inputs to be read.

The LPCI-7250 and LPCIe-7250 are low-profile boards that do not support
the plug-in modules, but except for a newer variant of the LPCIe-7250,
they cannot be distinguished from the full-height boards by their PCI
IDs.  For the newer variant of the LPCIe-7250, we can assume that there
are no plug-in modules fitted and limit the number of channels
accordingly.  This newer variant of the LPCIe-7250 uses memory-mapped
registers, whereas all the other boards use port-mapped registers.

I have tested the PCI-7250.  The new variant of the LPCIe-7250 has been
tested in an out-of-tree version of the Comedi drivers by someone else.

Tested-by: Ian Abbott <abbotti@mev.co.uk> # PCI-7250 only
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20250821145914.10445-1-abbotti@mev.co.uk


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