linux-kernel - Re: [PATCH] drivers: CCI: Correct use of ! and &

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Message-ID: <9hhwqb42k63.fsf@arm.com>
Date:	Wed, 23 Jul 2014 16:01:56 +0100
From:	Punit Agrawal <punit.agrawal@....com>
To:	Himangi Saraogi <himangi774@...il.com>
Cc:	linux-kernel@...r.kernel.org, julia.lawall@...6.fr,
	linux-arm-kernel@...ts.infradead.org, will.deacon@....com
Subject: Re: [PATCH] drivers: CCI: Correct use of ! and &

Adding alkml and Will

Hi Himangi,

In future it would help if you send the patch to the the maintainers by
running the get_maintainers.pl script on the patch.

Himangi Saraogi <himangi774@...il.com> writes:

> In commit ae91d60ba88ef0bdb1b5e9b2363bd52fc45d2af7, a bug was fixed that
> involved converting !x & y to !(x & y).  The code below shows the same
> pattern, and thus should perhaps be fixed in the same way.
>
> The Coccinelle semantic patch that makes this change is as follows:
>
> // <smpl>
> @@ expression E1,E2; @@
> (
>   !E1 & !E2
> |
> - !E1 & E2
> + !(E1 & E2)
> )
> // </smpl>
>
> Signed-off-by: Himangi Saraogi <himangi774@...il.com>
> Acked-by: Julia Lawall <julia.lawall@...6.fr>
> ---
> This is not tested and clearly changes the semantics, so it is only
> something to consider.
>  drivers/bus/arm-cci.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c
> index 5a86da9..7af78df 100644
> --- a/drivers/bus/arm-cci.c
> +++ b/drivers/bus/arm-cci.c
> @@ -397,7 +397,8 @@ static irqreturn_t pmu_handle_irq(int irq_num, void *dev)
>  		hw_counter = &event->hw;
>  
>  		/* Did this counter overflow? */
> -		if (!pmu_read_register(idx, CCI_PMU_OVRFLW) & CCI_PMU_OVRFLW_FLAG)
> +		if (!(pmu_read_register(idx, CCI_PMU_OVRFLW) &
> +		      CCI_PMU_OVRFLW_FLAG))
>  			continue;


Going back to the manual, this fix looks correct.

Acked-by: Punit Agrawal <punit.agrawal@....com>

Will, would this go via your tree?

>  
>  		pmu_write_register(CCI_PMU_OVRFLW_FLAG, idx, CCI_PMU_OVRFLW);
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