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SubjectRe: [PATCH 3/5] drivers/scsi: Use DIV_ROUND_CLOSEST
On Sat, 1 Aug 2009, Julia Lawall wrote:

> From: Julia Lawall <julia@diku.dk>
>
> The kernel.h macro DIV_ROUND_CLOSEST performs the computation (x + d/2)/d
> but is perhaps more readable.
>
> The semantic patch that makes this change is as follows:
> (http://www.emn.fr/x-info/coccinelle/)
>
> // <smpl>
> @haskernel@
> @@
>
> #include <linux/kernel.h>
>
> @depends on haskernel@
> expression x,__divisor;
> @@
>
> - (((x) + ((__divisor) / 2)) / (__divisor))
> + DIV_ROUND_CLOSEST(x,__divisor)
> // </smpl>
>
> Signed-off-by: Julia Lawall <julia@diku.dk>
>
> ---
> drivers/scsi/tmscsim.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> Diff --git a/drivers/scsi/tmscsim.c b/drivers/scsi/tmscsim.c
> index 9a42734..7322f30 100644
> --- a/drivers/scsi/tmscsim.c
> +++ b/drivers/scsi/tmscsim.c
> @@ -1125,7 +1125,8 @@ dc390_MsgIn_set_sync (struct dc390_acb* pACB, struct dc390_srb* pSRB)
> {
> if (! (bval & FAST_SCSI)) wval1++;
> printk (KERN_INFO "DC390: Target %i: Sync transfer %i.%1i MHz, Offset %i\n", pDCB->TargetID,
> - 40/wval1, ((40%wval1)*10+wval1/2)/wval1, pDCB->SyncOffset & 0x0f);
> + 40/wval1, DIV_ROUND_CLOSEST((40 % wval1) * 10, wval1),
> + pDCB->SyncOffset & 0x0f);
> }
>
> dc390_reprog (pACB, pDCB);

With all my respect to these scripted clean-up efforts, I am not sure this
really improves anything. I.e., I am not sure, that

z = DIV_ROUND_CLOSEST(x, y);

is better readable than

z = (x + y / 2) / y;

Besides, I do realise, that tmscsim.c indentation is dreadful (legacy
code...) but this patch changes it further from

printk("...",
x,
y);

to

printk("...",
x,
y);

which doesn't seem like an improvement to me either. That said, this does
compile, and I don't see why this shouldn't work, so, if we really want
this change here's the

Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/


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