Messages in this thread Patch in this message | | | Date | Sun, 12 Aug 2007 03:21:57 +0200 | From | Rene Herman <> | Subject | [PATCH] Re: cciss: warning: right shift count >= width of type |
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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. 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; | |