linux-kernel - Re: [MeeGo-Dev][PATCH] Topcliff: Update PCH

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Date:	Tue, 31 Aug 2010 22:24:14 -0700
From:	Joe Perches <joe@...ches.com>
To:	Masayuki Ohtake <masa-korg@....okisemi.com>
Cc:	"Jean Delvare (PC drivers, core)" <khali@...ux-fr.org>,
	"Ben Dooks (embedded platforms)" <ben-linux@...ff.org>,
	Crane Cai <crane.cai@....com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	srinidhi kasagar <srinidhi.kasagar@...ricsson.com>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Wang Yong Y\"" <yong.y.wang@...el.com>,
	"Wang Qi\"" <qi.wang@...el.com>,
	"Andrew\"" <andrew.chih.howe.khor@...el.com>,
	arjan@...ux.intel.com,
	Tomoya MORINAGA <morinaga526@....okisemi.com>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [MeeGo-Dev][PATCH] Topcliff: Update PCH_I2C driver to 2.6.35

On Wed, 2010-09-01 at 14:08 +0900, Masayuki Ohtake wrote:
> I have a question.
> Current our I2C driver  has the following 2 patterns dev_err().
> (1) dev_err(adap->pch_adapter.dev.parent, "...");
> (2) dev_err(&pdev->dev, "...");
> > #define pch_err(adap, fmt, arg...) \
> > dev_err(adap->pch_adapter.dev.parent, fmt, ##arg)
> In case of using the above code, pattern (1) can apply, but (2) can't.
> As to (2),
> Should we use as dev_err or define another macro?

Hello Ohtake.

To me, it's a visual complexity vs std pattern trade-off.

A 2 level dereference like dev_info(&dev->dev, ...)
isn't overly difficult to read.
3 or more dereferences can be harder and a bit error prone.
So I would only use pch_<level> for (1) and dev_err for (2).

There are also times when there are additional standard
arguments that you want to prefix to dev_<level> calls
and that can be simplified with a custom XXX_<level>
define for dev_<level>

Look at the current uses in the tree and see what you like.

$ grep -rP --include=*.[ch] "#define\s*.+\s+dev_[a-z]{3,7}\s*\(" *

These aren't requirements, do what you think best.

cheers, Joe

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