linux-kernel - [PATCH v3 08/13] comedi: ni_labpc_common: Conditionally remove I/O port support

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Message-Id: <20230913170712.111719-9-abbotti@mev.co.uk>
Date:   Wed, 13 Sep 2023 18:07:07 +0100
From:   Ian Abbott <abbotti@....co.uk>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ian Abbott <abbotti@....co.uk>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>,
        Arnd Bergmann <arnd@...nel.org>,
        Niklas Schnelle <schnelle@...ux.ibm.com>
Subject: [PATCH v3 08/13] comedi: ni_labpc_common: 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 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@...nel.org>
Cc: Niklas Schnelle <schnelle@...ux.ibm.com>
Signed-off-by: Ian Abbott <abbotti@....co.uk>
---
v2: Correct `CONFIG_HAS_PORTIO` to `CONFIG_HAS_IOPORT`.  Edit commit
message to describe run-time check in `labpc_common_attach()`, and to
mention that the changes allow the module to be built even if the port
I/O functions have not been declared.
v3: N/A.
---
 drivers/comedi/drivers/ni_labpc_common.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/comedi/drivers/ni_labpc_common.c b/drivers/comedi/drivers/ni_labpc_common.c
index 5d5c1d0e9cb6..7e0ce0ce0adf 100644
--- a/drivers/comedi/drivers/ni_labpc_common.c
+++ b/drivers/comedi/drivers/ni_labpc_common.c
@@ -78,6 +78,9 @@ static const struct comedi_lrange range_labpc_ao = {
  * functions that do inb/outb and readb/writeb so we can use
  * function pointers to decide which to use
  */
+
+#ifdef CONFIG_HAS_IOPORT
+
 static unsigned int labpc_inb(struct comedi_device *dev, unsigned long reg)
 {
 	return inb(dev->iobase + reg);
@@ -89,6 +92,8 @@ static void labpc_outb(struct comedi_device *dev,
 	outb(byte, dev->iobase + reg);
 }
 
+#endif	/* CONFIG_HAS_IOPORT */
+
 static unsigned int labpc_readb(struct comedi_device *dev, unsigned long reg)
 {
 	return readb(dev->mmio + reg);
@@ -1200,8 +1205,12 @@ int labpc_common_attach(struct comedi_device *dev,
 		devpriv->read_byte = labpc_readb;
 		devpriv->write_byte = labpc_writeb;
 	} else {
+#ifdef CONFIG_HAS_IOPORT
 		devpriv->read_byte = labpc_inb;
 		devpriv->write_byte = labpc_outb;
+#else
+		return -ENXIO;
+#endif
 	}
 
 	/* initialize board's command registers */
-- 
2.40.1