On Thu, 2021-06-03 at 19:06 +0100, Jonathan Cameron wrote: > From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > > A wrong use of one of these in > https://lore.kernel.org/linux-iio/20210514135927.2926482-1-arnd@xxxxxxxxxx/ > included a reference from Nathan to a patch discouraging the use of > these strings in general: > https://lore.kernel.org/lkml/CAHk-=wgoxnmsj8GEVFJSvTwdnWm8wVJthefNk2n6+4TC=20e0Q@xxxxxxxxxxxxxx/ > > I did a quick grep and established we only have a few instances of these in > IIO anyway, so in the interests of avoiding those existing cases getting > cut and paste into new drivers, let's just clear them out now. > > Note that patch from Arnd is now also part of this series, due to the > length specifier related issue Joe raised. > > I have chosen to go with 0x%02x rather than %#04x as I find it more readable. > > V2: > Use 0x%02x (Joe Perches) > Include Arnd's original patch, modified for the above. Hello again. It looks to me as though %#<foo> is relatively commonly misused in the kernel. Pehaps for the decimal portion of the format, checkpatch could have some test for use of non-standard lengths. Given the use is generally meant for a u8, u16, u32, or u64, perhaps checkpatch should emit a warning whenever the length is not 4, 6, 10, or 18. (possible checkpatch patch below) $ git grep -P -h -o '%#\d+\w+' | sort | uniq -c | sort -rn 392 %#08x 238 %#04x 144 %#02x 114 %#06x 92 %#010x 58 %#010Lx 55 %#018llx 47 %#010llx 45 %#010lx 38 %#016llx 27 %#0x 23 %#2x 18 %#016lx 17 %#3lx 17 %#08lx 17 %#018Lx 15 %#3x 14 %#03x 10 %#06hx 9 %#08zx 8 %#10x 7 %#16llx 6 %#8x 6 %#04X 6 %#04llx 6 %#012llx 5 %#16 4 %#08llx 4 %#06llx 4 %#05x 4 %#02X 4 %#016Lx 3 %#04hx 3 %#01x 2 %#6x 2 %#4x 2 %#10 2 %#09x 2 %#05lx 1 %#8lx 1 %#5x 1 %#5lx 1 %#2Lx 1 %#2llx 1 %#16x 1 %#16lx 1 %#12x 1 %#0x10000 1 %#0lx 1 %#08 1 %#05llx 1 %#04o 1 %#04lx 1 %#03X 1 %#018lx 1 %#010zx --- scripts/checkpatch.pl | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index d65334588eb4c..5840f3f2aee6f 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -6695,6 +6695,31 @@ sub process { my $fmt = get_quoted_string($lines[$count - 1], raw_line($count, 0)); $fmt =~ s/%%//g; + while ($fmt =~ /\%#([\d]+)/g) { + my $length = $1; + my $pref_len; + if ($length < 4) { + $pref_len = '04'; + } elsif ($length == 5) { + $pref_len = '06'; + } elsif ($length > 6 && $length < 10) { + $pref_len = '010'; + } elsif ($length > 10 && $length < 18) { + $pref_len = '018'; + } elsif ($length > 18) { + $pref_len = '<something else>'; + } + if (defined($pref_len)) { + if (!defined($stat_real)) { + $stat_real = get_stat_real($linenr, $lc); + } + WARN("VSPRINTF_SPECIAL_LENGTH", + "Unusual special length '%#$length' in 0x prefixed output, length is usually 2 more than the desired width - perhaps use '%#${pref_len}'\n" . "$here\n$stat_real"); + } + } + + pos($fmt) = 0; + while ($fmt =~ /(\%[\*\d\.]*p(\w)(\w*))/g) { $specifier = $1; $extension = $2;
