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    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.
    >

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