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Date:   Fri, 13 Mar 2020 12:08:04 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Bart Van Assche <bvanassche@acm.org>
Cc:     "Martin K . Petersen" <martin.petersen@oracle.com>,
        "James E . J . Bottomley" <jejb@linux.vnet.ibm.com>,
        linux-scsi@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Kai Makisara <Kai.Makisara@kolumbus.fi>,
        "James E . J . Bottomley" <jejb@linux.ibm.com>
Subject: Re: [PATCH v2 4/5] scsi/st: Use get_unaligned_be24() and
 sign_extend32()
Message-ID: <20200313110804.GC8132@lst.de>
References: <20200313023718.21830-1-bvanassche@acm.org> <20200313023718.21830-5-bvanassche@acm.org>
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On Thu, Mar 12, 2020 at 07:37:17PM -0700, Bart Van Assche wrote:
> @@ -2680,8 +2681,7 @@ static void deb_space_print(struct scsi_tape *STp, int direction, char *units, u
>  	if (!debugging)
>  		return;
>  
> -	sc = cmd[2] & 0x80 ? 0xff000000 : 0;
> -	sc |= (cmd[2] << 16) | (cmd[3] << 8) | cmd[4];
> +	sc = sign_extend32(get_unaligned_be24(&cmd[2]), 23);

Btw, didn't the old code here have undefined behavior if cmd[] is
a u8 and we shift by a larger amount?