lkml.org 
[lkml]   [2007]   [Aug]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Re: cciss: warning: right shift count >= width of type
On 08/12/2007 03:25 AM, Rene Herman wrote:

> On 08/12/2007 02:56 AM, Jesper Juhl wrote:
>
>> (whoops, forgot to add maintainer to Cc - now added)
>
> Ehm... too late...

Useless followup though -- hp.com rejects me as it feels the SPF neutral
results gmail sends due to me not using the gmail SMTP server and/or web
interface is something it wants to listen to.

I see you are @gmail as well, which depending on how you use it might mean
your are also not able to reach @hp. If anyone can get HP to fix their mail
setup, that'd be useful.

Rene.


>
>> On 12/08/07, Jesper Juhl <jesper.juhl@gmail.com> wrote:
>>> Hi,
>>>
>>> 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.
>

-
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/

\
 
 \ /
  Last update: 2007-08-12 04:01    [from the cache]
©2003-2011 Jasper Spaans