linux-kernel - Re: [PATCH 15/15] Staging: comedi: fix macro coding style issue in adl

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Date:	Wed, 10 Mar 2010 08:49:28 -0800
From:	Joe Perches <joe@...ches.com>
To:	Maurice Dawson <mauricedawson2699@...glemail.com>
Cc:	gregkh@...e.de, wfp5p@...ginia.edu, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/15] Staging: comedi: fix macro coding style issue in
 adl_pci9111.c

On Wed, 2010-03-10 at 14:02 +0000, Maurice Dawson wrote: 
> fixes, ERROR: Macros with multiple statements
> should be enclosed in a do - while block,
> found by the checkpatch.pl tool

Hello Maurice.

do {} while (0) macros should not use a trailing semicolon.
This allows the macro to be used in single statement if/else.

for example:

#define foo(a, b, c)	\
do {			\
	x = (a);	\
	y = (b);	\
	z = (c);	\
} while (0)

use:

	if (test)
		foo(1, 2, 3);
	else
		foo(4, 5, 6);

> #define pci9111_fifo_reset() \
> -  outb(PCI9111_FFEN_SET_FIFO_ENABLE, \
> -    PCI9111_IO_BASE+PCI9111_REGISTER_INTERRUPT_CONTROL); \
> -  outb(PCI9111_FFEN_SET_FIFO_DISABLE, \
> -    PCI9111_IO_BASE+PCI9111_REGISTER_INTERRUPT_CONTROL); \
> -  outb(PCI9111_FFEN_SET_FIFO_ENABLE, \
> -    PCI9111_IO_BASE+PCI9111_REGISTER_INTERRUPT_CONTROL)
> +	do { \
> +		outb(PCI9111_FFEN_SET_FIFO_ENABLE, \
> +			PCI9111_IO_BASE+PCI9111_REGISTER_INTERRUPT_CONTROL); \
> +		outb(PCI9111_FFEN_SET_FIFO_DISABLE, \
> +			PCI9111_IO_BASE+PCI9111_REGISTER_INTERRUPT_CONTROL); \
> +		outb(PCI9111_FFEN_SET_FIFO_ENABLE, \
> +			PCI9111_IO_BASE+PCI9111_REGISTER_INTERRUPT_CONTROL); \
> +	} while (0);

etc.

Also, there's a lot of uppercase and variable reuse in this macro
that makes it a bit difficult to parse and verify.

A couple more defines or a static inline could help.

Perhaps something like:

static inline void pci9111_fifo_reset(void)
{
	unsigned long addr = PCI9111_IO_BASE + PCI9111_REGISTER_INTERRUPT_CONTROL;

	outb(PCI9111_FFEN_SET_FIFO_ENABLE, addr);
	outb(PCI9111_FFEN_SET_FIFO_DISABLE, addr);
	outb(PCI9111_FFEN_SET_FIFO_ENABLE, addr);
}


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