On Thu, 2020-12-24 at 14:14 -0800, Tom Rix wrote:
> On 12/24/20 12:21 PM, Simon Horman wrote:
> > On Wed, Dec 23, 2020 at 12:20:53PM -0800, trix@xxxxxxxxxx wrote:
> > > From: Tom Rix <trix@xxxxxxxxxx>
> > >
> > > This change fixes the checkpatch warning described in this commit
> > > commit cbacb5ab0aa0 ("docs: printk-formats: Stop encouraging use of unnecessary %h[xudi] and %hh[xudi]")
> > >
> > > Standard integer promotion is already done and %hx and %hhx is useless
> > > so do not encourage the use of %hh[xudi] or %h[xudi].
> > >
> > > Signed-off-by: Tom Rix <trix@xxxxxxxxxx>
> > Hi Tom,
> >
> > This patch looks appropriate for net-next, which is currently closed.
> >
> > The changes look fine, but I'm curious to know if its intentionally that
> > the following was left alone in ethernet/netronome/nfp/nfp_net_ethtool.c:nfp_net_get_nspinfo()
> >
> > snprintf(version, ETHTOOL_FWVERS_LEN, "%hu.%hu"
>
> I am limiting changes to logging functions, what is roughly in checkpatch.
>
> I can add this snprintf in if you want.
I'm a bit confused here Tom.
I thought your clang-tidy script was looking for anything marked with
__printf() that is using %h[idux] or %hh[idux].
Wouldn't snprintf qualify for this already?
include/linux/kernel.h-extern __printf(3, 4)
include/linux/kernel.h:int snprintf(char *buf, size_t size, const char *fmt, ...);
Kernel code doesn't use a signed char or short with %hx or %hu very often
but in case you didn't already know, any signed char/short emitted with
anything like %hx or %hu needs to be left alone as sign extension occurs so:
signed char foo = -1;
printk("%hx", foo);
emits ffff but
printk("%x", foo);
emits ffffffff
An example:
$ gcc -x c -
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
signed short i = -1;
printf("hx: %hx\n", i);
printf("x: %x\n", i);
printf("hu: %hu\n", i);
printf("u: %u\n", i);
return 0;
}
$ ./a.out
hx: ffff
x: ffffffff
hu: 65535
u: 4294967295
$
