Re: [patch] staging: comedi: comedi_bond: silence a shift wrapping warning

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On 2013-08-21 13:45, Dan Carpenter wrote:
On Wed, Aug 21, 2013 at 11:50:22AM +0100, Ian Abbott wrote:
On 2013-08-21 09:27, Dan Carpenter wrote:
We set this using:

	devs_closed |= (0x1 << bdev->minor)

Since 0x1 is an int then only the lower 32 bits are usable before we hit
a shift wrapping bug.  There are some static checkers which complain
about this.  I've silenced the warning by making devs_closed a 32 bit
number.

32 bits should be enough for anybody.

Not really, as bdev->minor will be in the range 0 to 47 inclusive (0
to COMEDI_NUM_BOARD_MINORS-1).  Of course, an unsigned long is
insufficient too on a 32-bit system.

Ok.  I'll make it a u64 in a v2 patch.

If you want, we could drop that, and I could rework it to use DECLARE_BITMAP() and the functions in <linux/bitmap.h> to avoid assuming COMEDI_NUM_BOARD_MINORS is <= 64. The devs_opened[] in doDevConfig() could also be replaced by a bitmap (it's currently an array of pointers!).

--
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@xxxxxxxxx>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-
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