linux-kernel - Re: Coding style details (checkpatch)

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Date:	Sun, 21 Jun 2015 23:12:31 -0700
From:	Joe Perches <joe@...ches.com>
To:	Krzysztof Hałasa <khalasa@...p.pl>
Cc:	Frans Klaver <fransklaver@...il.com>,
	Andy Whitcroft <apw@...onical.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: Coding style details (checkpatch)

On Mon, 2015-06-22 at 07:33 +0200, Krzysztof Hałasa wrote:
> Joe Perches <joe@...ches.com> writes:
> 
> > How is the macro used?
> > #define REG8_1(a0) ((const u16[8]){a0, a0 + 1, a0 + 2, a0 + 3})
> 
> #define REG8_1(a0) ((const u16[8]){a0, a0 + 1, a0 + 2, a0 + 3, a0 + 4, a0 + 5, a0 + 6, a0 + 7})
[]
> #define VDMA_CHANNEL_CONFIG     REG8_1(0x10)
[]
>         reg_write(vc->dev, VDMA_CHANNEL_CONFIG[vc->ch], dma_cfg);
[]
> ERROR: space required before the open brace '{'
> +#define REG8_1(a0) ((const u16[8]){a0, a0 + 1, a0 + 2, a0 + 3})
> 
> Does this qualify as the "false positive"?

Probably, yes.  Is it worth fixing?  Probably not.

It might be better to use some base + index macro
as it could be smaller object code.

Something like:

#define REG_NO(base, multiplier, index)	(base + (multiplier * index))

	reg_write(vc->dev, REG_NO(0x10, 1, vc->ch), dma_cfg);
or

#define VDMA_CHANNEL_CONFIG	0x10

	reg_write(vc->dev, REG_NO(VDMA_CHANNEL_CONFIG, 1, vc->ch), dma_cfg);

etc...


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