linux-kernel - Re: [PATCH] scsi: remove useless variable assignment

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Message-ID: <20170518124107.Horde.TAwM83c0HSIrAfOVg_W7two@gator4166.hostgator.com>
Date:   Thu, 18 May 2017 12:41:07 -0500
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     James Bottomley <jejb@...ux.vnet.ibm.com>
Cc:     "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: remove useless variable assignment

Hi James,

Quoting James Bottomley <jejb@...ux.vnet.ibm.com>:

> On Wed, 2017-05-17 at 19:30 -0500, Gustavo A. R. Silva wrote:
>> Remove this assignment once the value stored in variable _k_ is
>> overwritten after a few lines.
>>
>> Addresses-Coverity-ID: 1226927
>> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
>> ---
>>  drivers/scsi/qlogicfas408.c | 1 -
>>  1 file changed, 1 deletion(-)
>>
>> diff --git a/drivers/scsi/qlogicfas408.c
>> b/drivers/scsi/qlogicfas408.c
>> index c3a9151..269440a 100644
>> --- a/drivers/scsi/qlogicfas408.c
>> +++ b/drivers/scsi/qlogicfas408.c
>> @@ -329,7 +329,6 @@ static unsigned int ql_pcmd(struct scsi_cmnd
>> *cmd)
>>  		 */
>>  		if ((k = ql_wai(priv)))
>>  			return (k << 16);
>> -		k = inb(qbase + 5);	/* should be 0x10, bus
>> service */
>
> That doesn't look right to me.  inb() is a statement which has an
> effect on the I/O device regardless of whether the returned value is
> used or discarded.  In this case I think it's being used to clear
> pending interrupts, so removing it will likely cause a phase error.
>

You are right, I get it.

In this case I think a patch to ignore the return value could be applied:

index c3a9151..8f5339a 100644
--- a/drivers/scsi/qlogicfas408.c
+++ b/drivers/scsi/qlogicfas408.c
@@ -329,7 +329,7 @@ static unsigned int ql_pcmd(struct scsi_cmnd *cmd)
                  */
                 if ((k = ql_wai(priv)))
                         return (k << 16);
-               k = inb(qbase + 5);     /* should be 0x10, bus service */
+               inb(qbase + 5); /* should be 0x10, bus service */
         }

What do you think?

Thank you for the clarification.
--
Gustavo A. R. Silva