On Mon, 2021-05-10 at 12:17 +0300, Michael Zaidman wrote: > On Sun, May 09, 2021 at 01:39:29PM -0700, Joe Perches wrote: > > On Sun, 2021-05-09 at 22:32 +0300, Michael Zaidman wrote: > > > Fixes: 6a82582d9fa4 ("HID: ft260: add usb hid to i2c host bridge driver") > > > > > > Fix warning reported by static analysis when built with W=1 for arm64 by > > > clang version 13.0.0 > > > > > > > > drivers/hid/hid-ft260.c:794:44: warning: format specifies type 'short' but > > > the argument has type 'int' [-Wformat] > > > return scnprintf(buf, PAGE_SIZE, "%hi\n", le16_to_cpu(*field)); > > > ~~~ ^~~~~~~~~~~~~~~~~~~ > > > %i > > > include/linux/byteorder/generic.h:91:21: note: expanded from > > > macro 'le16_to_cpu' > > > #define le16_to_cpu __le16_to_cpu > > > ^ > > > include/uapi/linux/byteorder/big_endian.h:36:26: note: expanded from > > > macro '__le16_to_cpu' > > > #define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x)) > > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > include/uapi/linux/swab.h:105:2: note: expanded from macro '__swab16' > > > (__builtin_constant_p((__u16)(x)) ? \ > > > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > > > > Signed-off-by: Michael Zaidman <michael.zaidman@xxxxxxxxx> > > > Reported-by: kernel test robot <lkp@xxxxxxxxx> > > > --- > > > drivers/hid/hid-ft260.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c > > > index 047aa85a7c83..38794a29599c 100644 > > > --- a/drivers/hid/hid-ft260.c > > > +++ b/drivers/hid/hid-ft260.c > > > @@ -791,7 +791,7 @@ static int ft260_word_show(struct hid_device *hdev, int id, u8 *cfg, int len, > > > if (ret != len && ret >= 0) > > > return -EIO; > > > > > > > > > - return scnprintf(buf, PAGE_SIZE, "%hi\n", le16_to_cpu(*field)); > > > + return scnprintf(buf, PAGE_SIZE, "%d\n", le16_to_cpu(*field)); > > > } > > > > There are 2 of these so I wonder about the static analysis. > > There is nothing wrong with the static analysis. The first scnprintf format > type is perfectly valid as far as its size is greater than the size of the > data pointed by the *field pointer, which is a one byte size in our case. > The static analysis warned about the second scnprintf case, where the format > type was shorter than the integer returned by the __builtin_constant_p. > This warning can be considered as a false positive since the le16_to_cpu is > all about the 16 bits numbers, but to silence it, I submitted the above fix. $ git grep __arch_swab16 arch/arm*/ arch/arm/include/asm/swab.h:#define __arch_swab16(x) ((__u16)__arch_swahb32(x)) otherwise: static inline __attribute_const__ __u16 __fswab16(__u16 val) { #if defined (__arch_swab16) return __arch_swab16(val); #else return ___constant_swab16(val); #endif } #define ___constant_swab16(x) ((__u16)( \ (((__u16)(x) & (__u16)0x00ffU) << 8) | \ (((__u16)(x) & (__u16)0xff00U) >> 8))) /** * __swab16 - return a byteswapped 16-bit value * @x: value to byteswap */ #ifdef __HAVE_BUILTIN_BSWAP16__ #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x)) #else #define __swab16(x) \ (__builtin_constant_p((__u16)(x)) ? \ ___constant_swab16(x) : \ __fswab16(x)) #endif Under what condition does the ?: return an int sized value rather than a u16 sized value? I fail to see a path where the compiler should promote the returned value to int _before_ the promotion done for the varargs use. If it's for the varargs use, then both instances are promoted. > > It's probably better to use sysfs_emit as well. > > The sysfs_emit was introduced in the 5.10 kernel: > 2efc459d06f16 (Joe Perches 2020-09-16 13:40:38 -0700 335) int sysfs_emit(...) > > But, the hid-ft260 driver will be used mostly with older kernels, at least, > for the next couple of years. Since older kernel versions do not have this API, > it will require patching the driver or kernel that I would like to avoid. > Nevertheless, we can reconsider the sysfs_emit usage in this driver in the > future, upon wider 5.10+ kernels' adoption. If this is only for older kernels, then it's not really useful upstream IMO. any sprintf style use of %h or %hh for a sub int sized value isn't particularly useful as integer promotion is done on the value so it should use %d (or %i, but %i is atypical) anyway. https://lore.kernel.org/lkml/CAHk-=wgoxnmsj8GEVFJSvTwdnWm8wVJthefNk2n6+4TC=20e0Q@xxxxxxxxxxxxxx/ $ git grep '%d\b' | wc -l 109922 $ git grep '%i\b' | wc -l 3508