linux-kernel - Re: rfc: checkpatch logical line continuations (was IBM Akebono: Add support for a new PHY interface to the IBM emac driver)

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Message-ID: <20140307213017.GA18769@cloud>
Date:	Fri, 7 Mar 2014 13:30:17 -0800
From:	josh@...htriplett.org
To:	Joe Perches <joe@...ches.com>
Cc:	David Miller <davem@...emloft.net>, alistair@...ple.id.au,
	netdev@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dan Carpenter <error27@...il.com>,
	Randy Dunlap <randy.dunlap@...cle.com>
Subject: Re: rfc: checkpatch logical line continuations (was IBM Akebono:
 Add support for a new PHY interface to the IBM emac driver)

On Fri, Mar 07, 2014 at 01:02:44PM -0800, Joe Perches wrote:
> On Fri, 2014-03-07 at 15:41 -0500, David Miller wrote:
> > From: Alistair Popple <alistair@...ple.id.au>
> > Date: Thu,  6 Mar 2014 14:52:25 +1100
> > 
> > > +	out_be32(dev->reg, in_be32(dev->reg) | WKUP_ETH_RGMIIEN
> > > +		 | WKUP_ETH_TX_OE | WKUP_ETH_RX_IE);
> > 
> > When an expression spans multiple lines, the lines should end with
> > operators rather than begin with them.
> 
> That's not in CodingStyle currently.

It's also not even remotely consistent across existing kernel code, and
it isn't obvious that there's a general developer consensus on the
"right" way to write it.

> Right now, checkpatch emits a --strict only warning on "&&" or "||"
> at the beginning of line but that could be changed to any "$Operators"
> 
> our $Arithmetic = qr{\+|-|\*|\/|%};
> our $Operators	= qr{
> 			<=|>=|==|!=|
> 			=>|->|<<|>>|<|>|!|~|
> 			&&|\|\||,|\^|\+\+|--|&|\||$Arithmetic
> 		  }x;
> 
> The ones that likely have a too high false positive rates
> are the negation "!" and bitwise "~".

I don't think warning about operators at start of line seems like a good
idea at all.  There are plenty of cases where putting the operator at
the start of the line will produce a better result.  (I'd actually
suggest that in *most* cases.)

> Also, using perl, it's hard to distinguish between a
> logical "&" and the address-of "&" as well as the
> multiplication "*" and indirection "*" so maybe those
> should be excluded too.
> 
> And I think it should only be added as a --strict test.

Agreed, if even that.

- Josh Triplett
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