Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765674AbXHLBm6 (ORCPT ); Sat, 11 Aug 2007 21:42:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757627AbXHLBmP (ORCPT ); Sat, 11 Aug 2007 21:42:15 -0400 Received: from smtpq2.tilbu1.nb.home.nl ([213.51.146.201]:42843 "EHLO smtpq2.tilbu1.nb.home.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754810AbXHLBmJ (ORCPT ); Sat, 11 Aug 2007 21:42:09 -0400 Message-ID: <46BE60B5.7010708@gmail.com> Date: Sun, 12 Aug 2007 03:21:57 +0200 From: Rene Herman User-Agent: Thunderbird 2.0.0.6 (X11/20070728) MIME-Version: 1.0 To: Jesper Juhl CC: linux-scsi@vger.kernel.org, Linux Kernel Mailing List Subject: [PATCH] Re: cciss: warning: right shift count >= width of type References: <200708120228.26234.jesper.juhl@gmail.com> In-Reply-To: <200708120228.26234.jesper.juhl@gmail.com> Content-Type: multipart/mixed; boundary="------------070202030002060105020500" X-AtHome-MailScanner-Information: Please contact support@home.nl for more information X-AtHome-MailScanner: Found to be clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3469 Lines: 94 This is a multi-part message in MIME format. --------------070202030002060105020500 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit On 08/12/2007 02:28 AM, Jesper Juhl wrote: > I've been building some randconfig kernels lately and I've noticed > this in a few builds : > > drivers/block/cciss.c:2614: warning: right shift count >= width of type > drivers/block/cciss.c:2615: warning: right shift count >= width of type > drivers/block/cciss.c:2616: warning: right shift count >= width of type > > The code in question is this : > > static void do_cciss_request(struct request_queue *q) > { > ... > sector_t start_blk; > ... > c->Request.CDB[2]= (start_blk >> 56) & 0xff; //MSB > c->Request.CDB[3]= (start_blk >> 48) & 0xff; > c->Request.CDB[4]= (start_blk >> 40) & 0xff; > ... > } > > > The problem stems from these lines in include/linux/types.h : > ... > #ifdef CONFIG_LBD > typedef u64 sector_t; > #else > typedef unsigned long sector_t; > #endif > ... > > So on a 32bit arch without CONFIG_LBD, sector_t is going to be 32 bits wide. > Thus it seems gcc is absolutely right in complaining about those > 56, 48 & 40 bit shifts, since they are indeed wider than the type > in the "!CONFIG_LBD on a 32bit arch" case. > > > I must admit that I have no idear what the proper way to deal with > that is, so I'll just report it so hopefully someone else can fix it. > > By the way; I'm building current Linus git tree, head at commit > ac07860264bd2b18834d3fa3be47032115524cea Well, given that it's explicitly treating start_blk as a 64-bit value, the proper fix is probably to cast start_blk to an actual (guaranteed) 64-bit value. Untested, uncompiled, and someone else may disagree: Rene. --------------070202030002060105020500 Content-Type: text/plain; name="cciss.diff" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="cciss.diff" diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c index 5acc6c4..fa2eec8 100644 --- a/drivers/block/cciss.c +++ b/drivers/block/cciss.c @@ -2609,13 +2609,13 @@ static void do_cciss_request(request_queue_t *q) } else { c->Request.CDBLen = 16; c->Request.CDB[1]= 0; - c->Request.CDB[2]= (start_blk >> 56) & 0xff; //MSB - c->Request.CDB[3]= (start_blk >> 48) & 0xff; - c->Request.CDB[4]= (start_blk >> 40) & 0xff; - c->Request.CDB[5]= (start_blk >> 32) & 0xff; - c->Request.CDB[6]= (start_blk >> 24) & 0xff; - c->Request.CDB[7]= (start_blk >> 16) & 0xff; - c->Request.CDB[8]= (start_blk >> 8) & 0xff; + c->Request.CDB[2]= ((u64)start_blk >> 56) & 0xff; //MSB + c->Request.CDB[3]= ((u64)start_blk >> 48) & 0xff; + c->Request.CDB[4]= ((u64)start_blk >> 40) & 0xff; + c->Request.CDB[5]= ((u64)start_blk >> 32) & 0xff; + c->Request.CDB[6]= ((u64)start_blk >> 24) & 0xff; + c->Request.CDB[7]= ((u64)start_blk >> 16) & 0xff; + c->Request.CDB[8]= ((u64)start_blk >> 8) & 0xff; c->Request.CDB[9]= start_blk & 0xff; c->Request.CDB[10]= (creq->nr_sectors >> 24) & 0xff; c->Request.CDB[11]= (creq->nr_sectors >> 16) & 0xff; --------------070202030002060105020500-- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/