Messages in this thread | | | Date | Wed, 1 Jul 2015 15:33:11 -0700 | From | Dmitry Torokhov <> | Subject | Re: RFC: kernel coding style: prefer array to &array[0] ? |
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On Wed, Jul 01, 2015 at 07:53:44AM -0700, Joe Perches wrote: > On Wed, 2015-07-01 at 14:26 +0200, Julia Lawall wrote: > > On Wed, 1 Jul 2015, Dan Carpenter wrote: > > > On Wed, Jul 01, 2015 at 01:54:29PM +0200, Clemens Ladisch wrote: > > > > Joe Perches wrote: > > > > > It seems most in-kernel uses are 'array' rather than '&array[0]' > > > > > > > > > > Most of the time, using array is simpler to read than &array[0]. > > > > > > > > > > Exceptions exists when addresses for consecutive members are > > > > > used like func(&array[0], &array[1]); > > > > > > > > I use '&array[0]' when I want to get a pointer to a single object that > > > > happens to be the first one in an array. > > > > > > Yeah. Of course, you're right. Otherwise it ends up confusing static > > > checkers if you want the first element or the whole array. > > Right. > > > > > > Should this preference be put into checkpatch and/or CodingStyle? > > And checkpatch will have no idea what the prototype > for any function is, so this transform is better left > for smarter tools like coccinelle. > > The proper answer here is no. > > > > > How about the following low-hanging fruit? > > > > > > > > foo(..., &array[0], ARRAY_SIZE(array), ...) > > > > > > Yes, to this also. I doubt checkpatch.pl will find a meaningful number > > > of these but doing that is annoying thing. > > > > Atcually, I find 236 of them, in 48 files. > > The uses I found: > > drivers/input/touchscreen nas a few
I got curious so I ran the proposed patch over drivers/input/touchscreen and it produced the following gems:
CHECK: Using addressof array 'data' index [0] may be simpler as 'data' #49: FILE: drivers/input/touchscreen/dynapro.c:49: +#define DYNAPRO_GET_TOUCHED(data) (DYNAPRO_FORMAT_TOUCH_BIT & data[0])
CHECK: Using addressof array 'mtouch->data' index [0] may be simpler as 'mtouch->data' #97: FILE: drivers/input/touchscreen/mtouch.c:97: + if (MTOUCH_FORMAT_TABLET_STATUS_BIT & mtouch->data[0])
... etc.
While below can be written as just "msg" in many cases when you parse several fields in the structure the original is actually cleaner:
CHECK: Using addressof array 'msg' index [0] may be simpler as 'msg' #38: FILE: drivers/input/touchscreen/ipaq-micro-ts.c:38: + be16_to_cpup((__be16 *) &msg[0]));
I'd be OK with changing cases like:
CHECK: Using addressof array 'buf' index [0] may be simpler as 'buf' #232: FILE: drivers/input/touchscreen/zforce_ts.c:232: + return zforce_send_wait(ts, &buf[0], ARRAY_SIZE(buf));
Thanks.
-- Dmitry
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