comedi: comedi_8255: Correct error in subdevice initialization

The refactoring done in commit 5c57b1ccecc7 ("comedi: comedi_8255: Rework
subdevice initialization functions") to the initialization of the io
field of struct subdev_8255_private broke all cards using the
drivers/comedi/drivers/comedi_8255.c module.

Prior to 5c57b1ccecc7, __subdev_8255_init() initialized the io field
in the newly allocated struct subdev_8255_private to the non-NULL
callback given to the function, otherwise it used a flag parameter to
select between subdev_8255_mmio and subdev_8255_io. The refactoring
removed that logic and the flag, as subdev_8255_mm_init() and
subdev_8255_io_init() now explicitly pass subdev_8255_mmio and
subdev_8255_io respectively to __subdev_8255_init(), only
__subdev_8255_init() never sets spriv->io to the supplied
callback. That spriv->io is NULL leads to a later BUG:

BUG: kernel NULL pointer dereference, address: 0000000000000000
PGD 0 P4D 0
Oops: 0010 [#1] SMP PTI
CPU: 1 PID: 1210 Comm: systemd-udevd Not tainted 6.7.3-x86_64 #1
Hardware name: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffffa3f1c02d7b78 EFLAGS: 00010202
RAX: 0000000000000000 RBX: ffff91f847aefd00 RCX: 000000000000009b
RDX: 0000000000000003 RSI: 0000000000000001 RDI: ffff91f840f6fc00
RBP: ffff91f840f6fc00 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 000000000000005f R12: 0000000000000000
R13: 0000000000000000 R14: ffffffffc0102498 R15: ffff91f847ce6ba8
FS: 00007f72f4e8f500(0000) GS:ffff91f8d5c80000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000010540e000 CR4: 00000000000406f0
Call Trace:
<TASK>
? __die_body+0x15/0x57
? page_fault_oops+0x2ef/0x33c
? insert_vmap_area.constprop.0+0xb6/0xd5
? alloc_vmap_area+0x529/0x5ee
? exc_page_fault+0x15a/0x489
? asm_exc_page_fault+0x22/0x30
__subdev_8255_init+0x79/0x8d [comedi_8255]
pci_8255_auto_attach+0x11a/0x139 [8255_pci]
comedi_auto_config+0xac/0x117 [comedi]
? __pfx___driver_attach+0x10/0x10
pci_device_probe+0x88/0xf9
really_probe+0x101/0x248
__driver_probe_device+0xbb/0xed
driver_probe_device+0x1a/0x72
__driver_attach+0xd4/0xed
bus_for_each_dev+0x76/0xb8
bus_add_driver+0xbe/0x1be
driver_register+0x9a/0xd8
comedi_pci_driver_register+0x28/0x48 [comedi_pci]
? __pfx_pci_8255_driver_init+0x10/0x10 [8255_pci]
do_one_initcall+0x72/0x183
do_init_module+0x5b/0x1e8
init_module_from_file+0x86/0xac
__do_sys_finit_module+0x151/0x218
do_syscall_64+0x72/0xdb
entry_SYSCALL_64_after_hwframe+0x6e/0x76
RIP: 0033:0x7f72f50a0cb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 47 71 0c 00 f7 d8 64 89 01 48
RSP: 002b:00007ffd47e512d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
RAX: ffffffffffffffda RBX: 0000562dd06ae070 RCX: 00007f72f50a0cb9
RDX: 0000000000000000 RSI: 00007f72f52d32df RDI: 000000000000000e
RBP: 0000000000000000 R08: 00007f72f5168b20 R09: 0000000000000000
R10: 0000000000000050 R11: 0000000000000246 R12: 00007f72f52d32df
R13: 0000000000020000 R14: 0000562dd06785c0 R15: 0000562dcfd0e9a8
</TASK>
Modules linked in: 8255_pci(+) comedi_8255 comedi_pci comedi intel_gtt e100(+) acpi_cpufreq rtc_cmos usbhid
CR2: 0000000000000000
---[ end trace 0000000000000000 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffffa3f1c02d7b78 EFLAGS: 00010202
RAX: 0000000000000000 RBX: ffff91f847aefd00 RCX: 000000000000009b
RDX: 0000000000000003 RSI: 0000000000000001 RDI: ffff91f840f6fc00
RBP: ffff91f840f6fc00 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 000000000000005f R12: 0000000000000000
R13: 0000000000000000 R14: ffffffffc0102498 R15: ffff91f847ce6ba8
FS: 00007f72f4e8f500(0000) GS:ffff91f8d5c80000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000010540e000 CR4: 00000000000406f0

This patch simply corrects the above mistake by initializing spriv->io
to the given io callback.

Fixes: 5c57b1ccecc7 ("comedi: comedi_8255: Rework subdevice initialization functions")
Signed-off-by: Frej Drejhammar <frej.drejhammar@gmail.com>
Cc: stable@vger.kernel.org
Acked-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20240211175822.1357-1-frej.drejhammar@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

comedi: comedi_8255: Conditionally remove I/O port support

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 comedi_8255 module supports both port I/O and memory-mapped I/O.

Conditionally compile the parts of the module that use port I/O if and
only if the `CONFIG_HAS_IOPORT` macro is defined so that it can still be
built if the port I/O functions have not been declared. If the
`CONFIG_HAS_IOPORT` macro is undefined, replace the GPL-exported
`subdev_8255_io_init()` function with a dummy static inline version that
just returns `-ENXIO`.

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/20230913170712.111719-8-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>

comedi: Move the main COMEDI headers

Move the main COMEDI driver headers out of "drivers/comedi/" into new
directory "include/linux/comedi/". These are "comedidev.h",
"comedilib.h", "comedi_pci.h", "comedi_pcmcia.h", and "comedi_usb.h".
Additionally, move the user-space API header "comedi.h" into
"include/uapi/linux/" and add "WITH Linux-syscall-note" to its
SPDX-License-Identifier.

Update the "COMEDI DRIVERS" section of the MAINTAINERS file to account
for these changes.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20211117120604.117740-2-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>