linux-kernel - Re: [PATCH] [SCSI] arcmsr: &/| confusion in arcmsr_build

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Date:	Sat, 1 Jan 2011 18:12:00 +0100
From:	Torsten Kaiser <just.for.lkml@...glemail.com>
To:	roel kluin <roel.kluin@...il.com>
Cc:	nick.cheng@...ca.com.tw, Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, James.Bottomley@...e.de,
	linux-scsi@...r.kernel.org
Subject: Re: [PATCH] [SCSI] arcmsr: &/| confusion in arcmsr_build_ccb()

On Sat, Jan 1, 2011 at 5:45 PM, roel kluin <roel.kluin@...il.com> wrote:
> The WRITE_{6,10,12} are defined numbers, so the branch was always taken.
>
> Signed-off-by: Roel Kluin <roel.kluin@...il.com>
> ---
>  drivers/scsi/arcmsr/arcmsr_hba.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
>
> See include/scsi/scsi.h:58-123 for
> #define WRITE_6               0x0a
> #define WRITE_10              0x2a
> #define WRITE_12              0xaa
>
> diff --git a/drivers/scsi/arcmsr/arcmsr_hba.c b/drivers/scsi/arcmsr/arcmsr_hba.c
> index 17e3df4..a6e5222 100644
> --- a/drivers/scsi/arcmsr/arcmsr_hba.c
> +++ b/drivers/scsi/arcmsr/arcmsr_hba.c
> @@ -1171,7 +1171,8 @@ static int arcmsr_build_ccb(struct AdapterControlBlock *acb,
>        arcmsr_cdb->msgPages = arccdbsize/0x100 + (arccdbsize % 0x100 ? 1 : 0);
>        if ( arccdbsize > 256)
>                arcmsr_cdb->Flags |= ARCMSR_CDB_FLAG_SGL_BSIZE;
> -       if (pcmd->cmnd[0]|WRITE_6 || pcmd->cmnd[0]|WRITE_10 || pcmd->cmnd[0]|WRITE_12 ){
> +       if (pcmd->cmnd[0] & WRITE_6 || pcmd->cmnd[0] & WRITE_10 ||
> +                       pcmd->cmnd[0] & WRITE_12 ){

I'm not sure, if the compiler will optimize this anyway, but would it
look better this way:
if (pcmd->cmnd[0] & (WRITE_6 | WRITE_10 | WRITE_12)){

And that would open the question what really was meant, as that will
be equal to:
if (pcmd->cmnd[0] & WRITE_12){

(if you look at the constants, you can skip WRITE_6 and _10 as there
bits are already included in WRITE_12)


>                arcmsr_cdb->Flags |= ARCMSR_CDB_FLAG_WRITE;
>        }
>        ccb->arc_cdb_size = arccdbsize;
> --
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