checkpatch: Adapt the braces check to Zephyr

scripts/checkpatch.pl was written originally for the Linux kernel, and
its code reflects the kernel's coding style. In particular, it has
checks for unneeded braces around single-statement if/else/for/while
conditions. In Zephyr however, braces are always required, and so the
checks needed modifying to verify the opposite condition.

In order to enable the now-compatible checks, we also remove the
--ignore BRACES statement in .checkpatch.conf.

Limitations: the current code works well if there are not conditional
statements (e.g. #if, #ifdef or #endif) next to the if/else/for/while
conditions. This is rarely the case, but triggers with the Bluetooth
controller in code like this:

```
 #if defined(CONFIG_BT_PERIPHERAL)
        if (!lll->is_hdcd)
 #endif /* CONFIG_BT_PERIPHERAL */
        {
```

```
        } else
 #endif /* CONFIG_BT_CTLR_PRIVACY */
        {

```

```
 #if defined(CONFIG_BT_CTLR_DF_ADV_CTE_TX)
        if (lll->cte_started) {
                radio_switch_complete(phy_s, 0, phy_s, 0);
        } else
 #endif /* CONFIG_BT_CTLR_DF_ADV_CTE_TX */
        {
```

```
 #ifdef DUAL_BANK
        while ((FLASH_STM32_REGS(dev)->SR1 & FLASH_SR_QW) ||
               (FLASH_STM32_REGS(dev)->SR2 & FLASH_SR_QW))
 #else
        while (FLASH_STM32_REGS(dev)->SR1 & FLASH_SR_QW)
 #endif
        {
```

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>

.checkpatch.conf

@@ -5,7 +5,6 @@
 --min-conf-desc-length=1
 --typedefsfile=scripts/checkpatch/typedefsfile
 
---ignore BRACES
 --ignore PRINTK_WITHOUT_KERN_LEVEL
 --ignore SPLIT_STRING
 --ignore VOLATILE

doc/contribute/guidelines.rst

@@ -545,8 +545,7 @@ exceptions:
 * The line length is 100 columns or fewer. In the documentation, longer lines
   for URL references are an allowed exception.
 * Add braces to every ``if``, ``else``, ``do``, ``while``, ``for`` and
-  ``switch`` body, even for single-line code blocks. Use the ``--ignore BRACES``
-  flag to make *checkpatch* stop complaining.
+  ``switch`` body, even for single-line code blocks.
 * Use spaces instead of tabs to align comments after declarations, as needed.
 * Use C89-style single line comments, ``/*  */``. The C99-style single line
   comment, ``//``, is not allowed.

scripts/checkpatch.pl

@@ -5497,8 +5497,9 @@ sub process {
 					my ($whitespace) = ($cond =~ /^((?:\s*\n[+-])*\s*)/s);
 					my $offset = statement_rawlines($whitespace) - 1;
 
-					$allowed[$allow] = 0;
-					#print "COND<$cond> whitespace<$whitespace> offset<$offset>\n";
+					# always allow braces (i.e. require them)
+					$allowed[$allow] = 1;
+					#print "COND<$cond> block<$block> whitespace<$whitespace> offset<$offset>\n";
 
 					# We have looked at and allowed this specific line.
 					$suppress_ifbraces{$ln + $offset} = 1;
@@ -5507,46 +5508,37 @@ sub process {
 					$ln += statement_rawlines($block) - 1;
 
 					substr($block, 0, length($cond), '');
+					#print "COND<$cond> block<$block>\n";
+
+					# Remove any 0x1C characters. The script replaces
+					# comments /* */ with those.
+					$block =~ tr/\x1C//d;
 
 					$seen++ if ($block =~ /^\s*{/);
 
-					#print "cond<$cond> block<$block> allowed<$allowed[$allow]>\n";
-					if (statement_lines($cond) > 1) {
-						#print "APW: ALLOWED: cond<$cond>\n";
-						$allowed[$allow] = 1;
-					}
-					if ($block =~/\b(?:if|for|while)\b/) {
-						#print "APW: ALLOWED: block<$block>\n";
-						$allowed[$allow] = 1;
-					}
-					if (statement_block_size($block) > 1) {
-						#print "APW: ALLOWED: lines block<$block>\n";
-						$allowed[$allow] = 1;
-					}
 					$allow++;
 				}
-				if ($seen) {
-					my $sum_allowed = 0;
-					foreach (@allowed) {
-						$sum_allowed += $_;
-					}
-					if ($sum_allowed == 0) {
-						WARN("BRACES",
-						     "braces {} are not necessary for any arm of this statement\n" . $herectx);
-					} elsif ($sum_allowed != $allow &&
-						 $seen != $allow) {
-						CHK("BRACES",
-						    "braces {} should be used on all arms of this statement\n" . $herectx);
-					}
+				my $sum_allowed = 0;
+				foreach (@allowed) {
+					$sum_allowed += $_;
+				}
+				#print "sum_allowed<$sum_allowed> seen<$seen> allow<$allow>\n";
+				if ($sum_allowed == 0) {
+					WARN("BRACES",
+					     "braces {} are not necessary for any arm of this statement\n" . $herectx);
+				} elsif ($seen != $allow) {
+					WARN("BRACES",
+					    "braces {} must be used on all arms 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, $-[0]) =~ /(\}\s*)$/) {
+			# Check the pre-context for:
+			# '#': #if
+			# '}': } while()
+			if (substr($line, 0, $-[0]) =~ /([\#\}]\s*)$/) {
 				#print "APW: ALLOWED: pre<$1>\n";
 				$allowed = 1;
 			}
@@ -5556,39 +5548,21 @@ sub process {
 
 			# Check the condition.
 			my ($cond, $block) = @{$chunks[0]};
-			#print "CHECKING<$linenr> cond<$cond> block<$block>\n";
+			#print "level $level CHECKING<$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) {
+			# Remove any 0x1C characters. The script replaces
+			# comments /* */ with those.
+			$block =~ tr/\x1C//d;
+			#print sprintf '%v02X', $block;
+			#print "\n";
+			if ($level == 0 && $block !~ /^\s*\{/ && !$allowed) {
 				my $cnt = statement_rawlines($block);
 				my $herectx = get_stat_here($linenr, $cnt, $here);
 
 				WARN("BRACES",
-				     "braces {} are not necessary for single statement blocks\n" . $herectx);
+				     "braces {} are required around if/while/for/else\n" . $herectx);
 			}
 		}