linux-kernel - Re: [GIT] Sparc

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Date:	Sat, 7 Nov 2015 14:31:08 +1100
From:	Julian Calaby <julian.calaby@...il.com>
To:	Julia Lawall <julia.lawall@...6.fr>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	sparclinux <sparclinux@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	kernel-janitors@...r.kernel.org
Subject: Re: [GIT] Sparc

Hi Julia,

On Fri, Nov 6, 2015 at 5:44 PM, Julia Lawall <julia.lawall@...6.fr> wrote:
> On Fri, 6 Nov 2015, Julian Calaby wrote:
>
>> Hi Linus,
>>
>> On Fri, Nov 6, 2015 at 11:56 AM, Linus Torvalds
>> <torvalds@...ux-foundation.org> wrote:
>> > On Thu, Nov 5, 2015 at 4:43 PM, Linus Torvalds
>> > <torvalds@...ux-foundation.org> wrote:
>> >>
>> >> Not that this *matters*, but it's a bit odd to have to cast constants
>> >> to perfectly regular C types.
>> >
>> > Looking around with "git grep", there's a few more of these.
>> >
>> >  - btrfs seems to like "(unsigned long)-1"
>> >
>> >    There's a few other users of that too, including more sparc uses.
>> >
>> >  - scsi/qla seems to like "(unsigned long)<hexnumber>"
>> >
>> >  - fmdrv_common.h seems to like "((unsigned long)1<<x)" for bitmaps
>> >
>> > along with a smattering of random noise all over of "(unsigned long)
>> > n" where 'n' is some integer.
>> >
>> > Apparently people aren't as aware of the normal "ul" postfix syntax as
>> > I would have expected. That said, it's a hundred-odd cases in all of
>> > the kernel, so it's still fairly rare.
>>
>> Maybe this is something the kernel-janitors team should look at? (CC'd)
>
> Do you have some concrete examples of the code that is undesirable?

Joe Perches produced a patch for checkpatch to check for this [1]

Linus was complaining [2] about people producing constants with casts
to basic C types in them. For instance:

#define IOMMU_ERROR_CODE (~(unsigned long) 0)

This could be replaced with

#define IOMMU_ERROR_CODE (~0ul)

or potentially

#define IOMMU_ERROR_CODE (-1ul)

It's not overly common, but it looks wrong.

Thanks,

Julian Calaby

[1] https://lkml.org/lkml/2015/11/6/48
[2] https://lkml.org/lkml/2015/11/5/785

-- 
Julian Calaby

Email: julian.calaby@...il.com
Profile: http://www.google.com/profiles/julian.calaby/
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