netdev - Re: rfc: bool structure members (was Re: [PATCH V3] net/mlx4: Get rid of page operation after dma_alloc

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Date:   Thu, 20 Dec 2018 18:40:02 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Bart Van Assche <bvanassche@....org>,
        Stephen Warren <swarren@...dotorg.org>,
        Tariq Toukan <tariqt@...lanox.com>, xavier.huwei@...wei.com,
        netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        Doug Ledford <dledford@...hat.com>,
        Stephen Warren <swarren@...dia.com>,
        Christoph Hellwig <hch@....de>, Jason Gunthorpe <jgg@...pe.ca>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: rfc: bool structure members (was Re: [PATCH V3] net/mlx4: Get
 rid of page operation after dma_alloc_coherent)

On Thu, 20 Dec 2018 18:25:05 -0800 Joe Perches <joe@...ches.com> wrote:

> On Thu, 2018-12-20 at 09:49 -0800, Bart Van Assche wrote:
> > On Thu, 2018-12-20 at 18:44 +0100, Christoph Hellwig wrote:
> > > On Thu, Dec 20, 2018 at 10:43:18AM -0700, Jason Gunthorpe wrote:
> > > > >   - chunk->coherent is an int not a bool since checkpatch complains about
> > > > >     using bool in structs; see https://lkml.org/lkml/2017/11/21/384.
> > > > 
> > > > :( bool is much more readable and there is no performance concern in
> > > > this struct. I think checkpatch is overzealous here.
> > > 
> > > Yes.  Nevermind that this for bool vs bitfield.  A int is worse in
> > > every respect in the criteria used in that mail.
> > 
> > (+Joe Perches)
> > 
> > Hi Joe,
> 
> Hi all.
> 
> > This is the second time that I see that the checkpatch complaint about using
> > bool in a structure leads kernel contributors to a bad decision. Please consider
> > removing that warning from checkpatch.
> 
> I agree it's not a very good message nor is bool use
> of structure members a real problem except in very
> few cases.
> 
> I think the message could either be restated and bool
> members described as OK for unshared memory structures.
> 
> Right now this is the test:
> 
> # check for bool use in .h files
> 		if ($realfile =~ /\.h$/ &&
> 		    $sline =~ /^.\s+bool\s*$Ident\s*(?::\s*d+\s*)?;/) {
> 			CHK("BOOL_MEMBER",
> 			    "Avoid using bool structure members because of possible alignment issues - see: https://lkml.org/lkml/2017/11/21/384\n" . $herecurr);

Probably better if this is in the tree. 
Documentation/process/coding-style.rst, perhaps.