cciss: warning: right shift count >= width of type

Jesper Juhl
2007-08-12T00:31:00Z

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

Kind regards,
Jesper Juhl