checkpatch.pl

			# Flatten any parentheses and braces
			while ($dstat =~ s/\([^\(\)]*\)/1/) {
			}
			while ($dstat =~ s/\{[^\{\}]*\}/1/) {
			}

			my $exceptions = qr{
				$Declare|
				module_param_named|
				MODULE_PARAM_DESC|
				DECLARE_PER_CPU|
				DEFINE_PER_CPU|
				__typeof__\(
			}x;
			#print "REST<$rest>\n";
			if ($rest ne '') {
				if ($rest !~ /while\s*\(/ &&
				    $dstat !~ /$exceptions/)
				{
					ERROR("Macros with multiple statements should be enclosed in a do - while loop\n" . "$here\n$ctx\n");
				}

			} elsif ($ctx !~ /;/) {
				if ($dstat ne '' &&
				    $dstat !~ /^(?:$Ident|-?$Constant)$/ &&
				    $dstat !~ /$exceptions/ &&
				    $dstat =~ /$Operators/)
				{
					ERROR("Macros with complex values should be enclosed in parenthesis\n" . "$here\n$ctx\n");
				}
			}
		}

# check for redundant bracing round if etc
		if ($line =~ /(^.*)\bif\b/ && $1 !~ /else\s*$/) {
			my ($level, $endln, @chunks) =
				ctx_statement_full($linenr, $realcnt, 1);
			#print "chunks<$#chunks> linenr<$linenr> endln<$endln> level<$level>\n";
			#print "APW: <<$chunks[1][0]>><<$chunks[1][1]>>\n";
			if ($#chunks > 0 && $level == 0) {
				my $allowed = 0;
				my $seen = 0;
				my $herectx = $here . "\n";
				my $ln = $linenr - 1;
				for my $chunk (@chunks) {
					my ($cond, $block) = @{$chunk};

					# If the condition carries leading newlines, then count those as offsets.
					my ($whitespace) = ($cond =~ /^((?:\s*\n[+-])*\s*)/s);
					my $offset = statement_rawlines($whitespace) - 1;

					#print "COND<$cond> whitespace<$whitespace> offset<$offset>\n";

					# We have looked at and allowed this specific line.
					$suppress_ifbraces{$ln + $offset} = 1;

					$herectx .= "$rawlines[$ln + $offset]\n[...]\n";
					$ln += statement_rawlines($block) - 1;

					substr($block, 0, length($cond), '');

					$seen++ if ($block =~ /^\s*{/);

					#print "cond<$cond> block<$block> allowed<$allowed>\n";
					if (statement_lines($cond) > 1) {
						#print "APW: ALLOWED: cond<$cond>\n";
						$allowed = 1;
					}
					if ($block =~/\b(?:if|for|while)\b/) {
						#print "APW: ALLOWED: block<$block>\n";
						$allowed = 1;
					}
					if (statement_block_size($block) > 1) {
						#print "APW: ALLOWED: lines block<$block>\n";
						$allowed = 1;
					}
				}
				if ($seen && !$allowed) {
					WARN("braces {} are not necessary for any arm of this statement\n" . $herectx);
				}
			}
		}
		if (!defined $suppress_ifbraces{$linenr - 1} &&
					$line =~ /\b(if|while|for|else)\b/) {
			my $allowed = 0;

			# Check the pre-context.
			if (substr($line, 0, $-[0]) =~ /(\}\s*)$/) {
				#print "APW: ALLOWED: pre<$1>\n";
				$allowed = 1;
			}

			my ($level, $endln, @chunks) =
				ctx_statement_full($linenr, $realcnt, $-[0]);

			# Check the condition.
			my ($cond, $block) = @{$chunks[0]};
			#print "CHECKING<$linenr> cond<$cond> block<$block>\n";
			if (defined $cond) {
				substr($block, 0, length($cond), '');
			}
			if (statement_lines($cond) > 1) {
				#print "APW: ALLOWED: cond<$cond>\n";
				$allowed = 1;
			}
			if ($block =~/\b(?:if|for|while)\b/) {
				#print "APW: ALLOWED: block<$block>\n";
				$allowed = 1;
			}
			if (statement_block_size($block) > 1) {
				#print "APW: ALLOWED: lines block<$block>\n";
				$allowed = 1;
			}
			# Check the post-context.
			if (defined $chunks[1]) {
				my ($cond, $block) = @{$chunks[1]};
				if (defined $cond) {
					substr($block, 0, length($cond), '');
				}
				if ($block =~ /^\s*\{/) {
					#print "APW: ALLOWED: chunk-1 block<$block>\n";
					$allowed = 1;
				}
			}
			if ($level == 0 && $block =~ /^\s*\{/ && !$allowed) {
				my $herectx = $here . "\n";;
				my $end = $linenr + statement_rawlines($block) - 1;

				for (my $ln = $linenr - 1; $ln < $end; $ln++) {
					$herectx .= $rawlines[$ln] . "\n";;
				}

				WARN("braces {} are not necessary for single statement blocks\n" . $herectx);
			}
		}

# don't include deprecated include files (uses RAW line)
		for my $inc (@dep_includes) {
			if ($rawline =~ m@^.\s*\#\s*include\s*\<$inc>@) {
				ERROR("Don't use <$inc>: see Documentation/feature-removal-schedule.txt\n" . $herecurr);
			}
		}

# don't use deprecated functions
		for my $func (@dep_functions) {
			if ($line =~ /\b$func\b/) {
				ERROR("Don't use $func(): see Documentation/feature-removal-schedule.txt\n" . $herecurr);
			}
		}

# no volatiles please
		my $asm_volatile = qr{\b(__asm__|asm)\s+(__volatile__|volatile)\b};
		if ($line =~ /\bvolatile\b/ && $line !~ /$asm_volatile/) {
			WARN("Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt\n" . $herecurr);
		}

# SPIN_LOCK_UNLOCKED & RW_LOCK_UNLOCKED are deprecated
		if ($line =~ /\b(SPIN_LOCK_UNLOCKED|RW_LOCK_UNLOCKED)/) {
			ERROR("Use of $1 is deprecated: see Documentation/spinlocks.txt\n" . $herecurr);
		}

# warn about #if 0
		if ($line =~ /^.\s*\#\s*if\s+0\b/) {
			CHK("if this code is redundant consider removing it\n" .
				$herecurr);
		}

# check for needless kfree() checks
		if ($prevline =~ /\bif\s*\(([^\)]*)\)/) {
			my $expr = $1;
			if ($line =~ /\bkfree\(\Q$expr\E\);/) {
				WARN("kfree(NULL) is safe this check is probably not required\n" . $hereprev);
			}
		}
# check for needless usb_free_urb() checks
		if ($prevline =~ /\bif\s*\(([^\)]*)\)/) {
			my $expr = $1;
			if ($line =~ /\busb_free_urb\(\Q$expr\E\);/) {
				WARN("usb_free_urb(NULL) is safe this check is probably not required\n" . $hereprev);
			}
		}

# warn about #ifdefs in C files
#		if ($line =~ /^.\s*\#\s*if(|n)def/ && ($realfile =~ /\.c$/)) {
#			print "#ifdef in C files should be avoided\n";
#			print "$herecurr";
#			$clean = 0;
#		}

# warn about spacing in #ifdefs
		if ($line =~ /^.\s*\#\s*(ifdef|ifndef|elif)\s\s+/) {
			ERROR("exactly one space required after that #$1\n" . $herecurr);
		}

# check for spinlock_t definitions without a comment.
		if ($line =~ /^.\s*(struct\s+mutex|spinlock_t)\s+\S+;/ ||
		    $line =~ /^.\s*(DEFINE_MUTEX)\s*\(/) {
			my $which = $1;
			if (!ctx_has_comment($first_line, $linenr)) {
				CHK("$1 definition without comment\n" . $herecurr);
			}
		}
# check for memory barriers without a comment.
		if ($line =~ /\b(mb|rmb|wmb|read_barrier_depends|smp_mb|smp_rmb|smp_wmb|smp_read_barrier_depends)\(/) {
			if (!ctx_has_comment($first_line, $linenr)) {
				CHK("memory barrier without comment\n" . $herecurr);
			}
		}
# check of hardware specific defines
		if ($line =~ m@^.\s*\#\s*if.*\b(__i386__|__powerpc64__|__sun__|__s390x__)\b@ && $realfile !~ m@include/asm-@) {
			CHK("architecture specific defines should be avoided\n" .  $herecurr);
		}

# check the location of the inline attribute, that it is between
# storage class and type.
		if ($line =~ /\b$Type\s+$Inline\b/ ||
		    $line =~ /\b$Inline\s+$Storage\b/) {
			ERROR("inline keyword should sit between storage class and type\n" . $herecurr);
		}

# Check for __inline__ and __inline, prefer inline
		if ($line =~ /\b(__inline__|__inline)\b/) {
			WARN("plain inline is preferred over $1\n" . $herecurr);
		}

# check for new externs in .c files.
		if ($realfile =~ /\.c$/ && defined $stat &&
		    $stat =~ /^.\s*(?:extern\s+)?$Type\s+($Ident)(\s*)\(/s)
		{
			my $function_name = $1;
			my $paren_space = $2;

			my $s = $stat;
			if (defined $cond) {
				substr($s, 0, length($cond), '');
			}
			if ($s =~ /^\s*;/ &&
			    $function_name ne 'uninitialized_var')
			{
				WARN("externs should be avoided in .c files\n" .  $herecurr);
			}

			if ($paren_space =~ /\n/) {
				WARN("arguments for function declarations should follow identifier\n" . $herecurr);
			}

		} elsif ($realfile =~ /\.c$/ && defined $stat &&
		    $stat =~ /^.\s*extern\s+/)
		{
			WARN("externs should be avoided in .c files\n" .  $herecurr);
		}

# checks for new __setup's
		if ($rawline =~ /\b__setup\("([^"]*)"/) {
			my $name = $1;

			if (!grep(/$name/, @setup_docs)) {
				CHK("__setup appears un-documented -- check Documentation/kernel-parameters.txt\n" . $herecurr);
			}
		}

# check for pointless casting of kmalloc return
		if ($line =~ /\*\s*\)\s*k[czm]alloc\b/) {
			WARN("unnecessary cast may hide bugs, see http://c-faq.com/malloc/mallocnocast.html\n" . $herecurr);
		}

# check for gcc specific __FUNCTION__
		if ($line =~ /__FUNCTION__/) {
			WARN("__func__ should be used instead of gcc specific __FUNCTION__\n"  . $herecurr);
		}

# check for semaphores used as mutexes
		if ($line =~ /^.\s*(DECLARE_MUTEX|init_MUTEX)\s*\(/) {
			WARN("mutexes are preferred for single holder semaphores\n" . $herecurr);
		}
# check for semaphores used as mutexes
		if ($line =~ /^.\s*init_MUTEX_LOCKED\s*\(/) {
			WARN("consider using a completion\n" . $herecurr);
		}
# recommend strict_strto* over simple_strto*
		if ($line =~ /\bsimple_(strto.*?)\s*\(/) {
			WARN("consider using strict_$1 in preference to simple_$1\n" . $herecurr);
		}
# check for __initcall(), use device_initcall() explicitly please
		if ($line =~ /^.\s*__initcall\s*\(/) {
			WARN("please use device_initcall() instead of __initcall()\n" . $herecurr);
		}

# use of NR_CPUS is usually wrong
# ignore definitions of NR_CPUS and usage to define arrays as likely right
		if ($line =~ /\bNR_CPUS\b/ &&
		    $line !~ /^.\s*\s*#\s*if\b.*\bNR_CPUS\b/ &&
		    $line !~ /^.\s*\s*#\s*define\b.*\bNR_CPUS\b/ &&
		    $line !~ /^.\s*$Declare\s.*\[[^\]]*NR_CPUS[^\]]*\]/ &&
		    $line !~ /\[[^\]]*\.\.\.[^\]]*NR_CPUS[^\]]*\]/ &&
		    $line !~ /\[[^\]]*NR_CPUS[^\]]*\.\.\.[^\]]*\]/)
		{
			WARN("usage of NR_CPUS is often wrong - consider using cpu_possible(), num_possible_cpus(), for_each_possible_cpu(), etc\n" . $herecurr);
		}

# check for %L{u,d,i} in strings
		my $string;
		while ($line =~ /(?:^|")([X\t]*)(?:"|$)/g) {
			$string = substr($rawline, $-[1], $+[1] - $-[1]);
			if ($string =~ /(?<!%)%L[udi]/) {
				WARN("\%Ld/%Lu are not-standard C, use %lld/%llu\n" . $herecurr);
				last;
			}
		}
	}

	# If we have no input at all, then there is nothing to report on
	# so just keep quiet.
	if ($#rawlines == -1) {
		exit(0);
	}

	# In mailback mode only produce a report in the negative, for
	# things that appear to be patches.
	if ($mailback && ($clean == 1 || !$is_patch)) {
		exit(0);
	}

	# This is not a patch, and we are are in 'no-patch' mode so
	# just keep quiet.
	if (!$chk_patch && !$is_patch) {
		exit(0);
	}

	if (!$is_patch) {
		ERROR("Does not appear to be a unified-diff format patch\n");
	}
	if ($is_patch && $chk_signoff && $signoff == 0) {
		ERROR("Missing Signed-off-by: line(s)\n");
	}

	print report_dump();
	if ($summary && !($clean == 1 && $quiet == 1)) {
		print "$filename " if ($summary_file);
		print "total: $cnt_error errors, $cnt_warn warnings, " .
			(($check)? "$cnt_chk checks, " : "") .
			"$cnt_lines lines checked\n";
		print "\n" if ($quiet == 0);
	}

	if ($clean == 1 && $quiet == 0) {
		print "$vname has no obvious style problems and is ready for submission.\n"
	}
	if ($clean == 0 && $quiet == 0) {
		print "$vname has style problems, please review.  If any of these errors\n";
		print "are false positives report them to the maintainer, see\n";
		print "CHECKPATCH in MAINTAINERS.\n";
	}

	return $clean;
}