Coding Style: Reverse XMAS tree declarations ? (was Re: [PATCH net-next v6 02/10] dpaa_eth: add support for DPAA Ethernet)

From: Joe Perches
Date: Fri Nov 04 2016 - 02:54:20 EST

On Thu, 2016-11-03 at 15:58 -0400, David Miller wrote:
> From: Madalin Bucur <madalin.bucur@xxxxxxx>
> Date: Wed, 2 Nov 2016 22:17:26 +0200
>
> > This introduces the Freescale Data Path Acceleration Architecture
> > +static inline size_t bpool_buffer_raw_size(u8 index, u8 cnt)
> > +{
> > +     u8 i;
> > +     size_t res = DPAA_BP_RAW_SIZE / 2;
>
> Always order local variable declarations from longest to shortest line,
> also know as Reverse Christmas Tree Format.

I think this declaration sorting order is misguided but
here's a possible change to checkpatch adding a test for it
that does this test just for net/ and drivers/net/

(this likely won't apply because Evolution is a horrible
email client for sending patches, but the attachment should)

An example output:

$ ./scripts/checkpatch.pl -f drivers/net/ethernet/ethoc.c --types=reverse_xmas_tree --show-types
CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to shortest
#200: FILE: drivers/net/ethernet/ethoc.c:200:
+ void __iomem *iobase;
+ void __iomem *membase;

CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to shortest
#202: FILE: drivers/net/ethernet/ethoc.c:202:
+ int dma_alloc;
+ resource_size_t io_region_size;

CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to shortest
#305: FILE: drivers/net/ethernet/ethoc.c:305:
+ int i;
+ void *vma;

CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to shortest
#446: FILE: drivers/net/ethernet/ethoc.c:446:
+ int size = bd.stat >> 16;
+ struct sk_buff *skb;

CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to shortest
#515: FILE: drivers/net/ethernet/ethoc.c:515:
+ int count;
+ struct ethoc_bd bd;

CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to shortest
#675: FILE: drivers/net/ethernet/ethoc.c:675:
+ struct ethoc *priv = netdev_priv(dev);
+ struct phy_device *phy;

CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to shortest
#756: FILE: drivers/net/ethernet/ethoc.c:756:
+ struct ethoc *priv = netdev_priv(dev);
+ struct mii_ioctl_data *mdio = if_mii(ifr);

CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to shortest
#801: FILE: drivers/net/ethernet/ethoc.c:801:
+ u32 mode = ethoc_read(priv, MODER);
+ struct netdev_hw_addr *ha;

CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to shortest
#996: FILE: drivers/net/ethernet/ethoc.c:996:
+ struct resource *res = NULL;
+ struct resource *mmio = NULL;

CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to shortest
#1001: FILE: drivers/net/ethernet/ethoc.c:1001:
+ int ret = 0;
+ bool random_mac = false;

CHECK:REVERSE_XMAS_TREE: Prefer ordering declarations longest to shortest
#1002: FILE: drivers/net/ethernet/ethoc.c:1002:
+ bool random_mac = false;
+ struct ethoc_platform_data *pdata = dev_get_platdata(&pdev->dev);

total: 0 errors, 0 warnings, 11 checks, 1297 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
mechanically convert to the typical style using --fix or --fix-inplace.

drivers/net/ethernet/ethoc.c has style problems, please review.

NOTE: Used message types: REVERSE_XMAS_TREE

NOTE: If any of the errors are false positives, please report
them to the maintainer, see CHECKPATCH in MAINTAINERS.
---
 scripts/checkpatch.pl | 70 ++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 56 insertions(+), 14 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index fdacd759078e..dd344ac77cb8 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2114,6 +2114,29 @@ sub pos_last_openparen {
  return length(expand_tabs(substr($line, 0, $last_openparen))) + 1;
 }
 
+sub get_decl {
+ my ($line) = @_;
+
+ # typical declarations
+ if ($line =~ /^\+\s+($Declare\s*$Ident)\s*[=,;:\[]/) {
+ return $1;
+ }
+ # function pointer declarations
+ if ($line =~ /^\+\s+($Declare\s*\(\s*\*\s*$Ident\s*\))\s*[=,;:\[\(]/) {
+ return $1;
+ }
+ # foo bar; where foo is some local typedef or #define
+ if ($line =~ /^\+\s+($Ident(?:\s+|\s*\*\s*)$Ident)\s*[=,;\[]/) {
+ return $1;
+ }
+ # known declaration macros
+ if ($line =~ /^\+\s+$(declaration_macros)/) {
+ return $1;
+ }
+
+ return undef;
+}
+
 sub process {
  my $filename = shift;
 
@@ -3063,9 +3086,7 @@ sub process {
  $last_blank_line = $linenr;
  }
 
-# check for missing blank lines after declarations
- if ($sline =~ /^\+\s+\S/ && #Not at char 1
- # actual declarations
+ my $prev_decl =
      ($prevline =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ ||
  # function pointer declarations
       $prevline =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ ||
@@ -3078,25 +3099,30 @@ sub process {
  # other possible extensions of declaration lines
        $prevline =~ /(?:$Compare|$Assignment|$Operators)\s*$/ ||
  # not starting a section or a macro "\" extended line
-       $prevline =~ /(?:\{\s*|\\)$/) &&
- # looks like a declaration
-     !($sline =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ ||
+       $prevline =~ /(?:\{\s*|\\)$/);
+ my $sline_decl =
+     $sline =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ ||
  # function pointer declarations
-       $sline =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ ||
+     $sline =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ ||
  # foo bar; where foo is some local typedef or #define
-       $sline =~ /^\+\s+$Ident(?:\s+|\s*\*\s*)$Ident\s*[=,;\[]/ ||
+     $sline =~ /^\+\s+$Ident(?:\s+|\s*\*\s*)$Ident\s*[=,;\[]/ ||
  # known declaration macros
-       $sline =~ /^\+\s+$declaration_macros/ ||
+     $sline =~ /^\+\s+$declaration_macros/ ||
  # start of struct or union or enum
-       $sline =~ /^\+\s+(?:union|struct|enum|typedef)\b/ ||
+     $sline =~ /^\+\s+(?:union|struct|enum|typedef)\b/ ||
  # start or end of block or continuation of declaration
-       $sline =~ /^\+\s+(?:$|[\{\}\.\#\"\?\:\(\[])/ ||
+     $sline =~ /^\+\s+(?:$|[\{\}\.\#\"\?\:\(\[])/ ||
  # bitfield continuation
-       $sline =~ /^\+\s+$Ident\s*:\s*\d+\s*[,;]/ ||
+     $sline =~ /^\+\s+$Ident\s*:\s*\d+\s*[,;]/ ||
  # other possible extensions of declaration lines
-       $sline =~ /^\+\s+\(?\s*(?:$Compare|$Assignment|$Operators)/) &&
+     $sline =~ /^\+\s+\(?\s*(?:$Compare|$Assignment|$Operators)/;
+
+# check for missing blank lines after declarations
+ if ($sline =~ /^\+\s+\S/ && #Not at char 1
+ # actual declarations
+     $prev_decl && !$sline_decl &&
  # indentation of previous and current line are the same
-     (($prevline =~ /\+(\s+)\S/) && $sline =~ /^\+$1\S/)) {
+     ($prevline =~ /\+(\s+)\S/ && $sline =~ /^\+$1\S/)) {
  if (WARN("LINE_SPACING",
   "Missing a blank line after declarations\n" . $hereprev) &&
      $fix) {
@@ -3104,6 +3130,22 @@ sub process {
  }
  }
 
+# check for reverse christmas tree declarations in net/ and drivers/net/
+ if ($realfile =~ m@^(?:drivers/net/|net/)@ &&
+     $sline =~ /^\+\s+\S/ && #Not at char 1
+ # actual declarations
+     $prev_decl && $sline_decl &&
+ # indentation of previous and current line are the same
+     (($prevline =~ /\+(\s+)\S/) && $sline =~ /^\+$1\S/)) {
+ my $p = get_decl($prevline);
+ my $l = get_decl($sline);
+ if (defined($p) && defined($l) && length($p) < length($l) &&
+     CHK("REVERSE_XMAS_TREE",
+ "Prefer ordering declarations longest to shortest\n" . $hereprev) &&
+     $fix) {
+ }
+ }
+
 # check for spaces at the beginning of a line.
 # Exceptions:
 #  1) within comments scripts/checkpatch.pl | 70 ++++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 56 insertions(+), 14 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index fdacd759078e..dd344ac77cb8 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2114,6 +2114,29 @@ sub pos_last_openparen {
return length(expand_tabs(substr($line, 0, $last_openparen))) + 1;
}

+sub get_decl {
+ my ($line) = @_;
+
+ # typical declarations
+ if ($line =~ /^\+\s+($Declare\s*$Ident)\s*[=,;:\[]/) {
+ return $1;
+ }
+ # function pointer declarations
+ if ($line =~ /^\+\s+($Declare\s*\(\s*\*\s*$Ident\s*\))\s*[=,;:\[\(]/) {
+ return $1;
+ }
+ # foo bar; where foo is some local typedef or #define
+ if ($line =~ /^\+\s+($Ident(?:\s+|\s*\*\s*)$Ident)\s*[=,;\[]/) {
+ return $1;
+ }
+ # known declaration macros
+ if ($line =~ /^\+\s+$(declaration_macros)/) {
+ return $1;
+ }
+
+ return undef;
+}
+
sub process {
my $filename = shift;

@@ -3063,9 +3086,7 @@ sub process {
$last_blank_line = $linenr;
}

-# check for missing blank lines after declarations
- if ($sline =~ /^\+\s+\S/ && #Not at char 1
- # actual declarations
+ my $prev_decl =
($prevline =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ ||
# function pointer declarations
$prevline =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ ||
@@ -3078,25 +3099,30 @@ sub process {
# other possible extensions of declaration lines
$prevline =~ /(?:$Compare|$Assignment|$Operators)\s*$/ ||
# not starting a section or a macro "\" extended line
- $prevline =~ /(?:\{\s*|\\)$/) &&
- # looks like a declaration
- !($sline =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ ||
+ $prevline =~ /(?:\{\s*|\\)$/);
+ my $sline_decl =
+ $sline =~ /^\+\s+$Declare\s*$Ident\s*[=,;:\[]/ ||
# function pointer declarations
- $sline =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ ||
+ $sline =~ /^\+\s+$Declare\s*\(\s*\*\s*$Ident\s*\)\s*[=,;:\[\(]/ ||
# foo bar; where foo is some local typedef or #define
- $sline =~ /^\+\s+$Ident(?:\s+|\s*\*\s*)$Ident\s*[=,;\[]/ ||
+ $sline =~ /^\+\s+$Ident(?:\s+|\s*\*\s*)$Ident\s*[=,;\[]/ ||
# known declaration macros
- $sline =~ /^\+\s+$declaration_macros/ ||
+ $sline =~ /^\+\s+$declaration_macros/ ||
# start of struct or union or enum
- $sline =~ /^\+\s+(?:union|struct|enum|typedef)\b/ ||
+ $sline =~ /^\+\s+(?:union|struct|enum|typedef)\b/ ||
# start or end of block or continuation of declaration
- $sline =~ /^\+\s+(?:$|[\{\}\.\#\"\?\:\(\[])/ ||
+ $sline =~ /^\+\s+(?:$|[\{\}\.\#\"\?\:\(\[])/ ||
# bitfield continuation
- $sline =~ /^\+\s+$Ident\s*:\s*\d+\s*[,;]/ ||
+ $sline =~ /^\+\s+$Ident\s*:\s*\d+\s*[,;]/ ||
# other possible extensions of declaration lines
- $sline =~ /^\+\s+\(?\s*(?:$Compare|$Assignment|$Operators)/) &&
+ $sline =~ /^\+\s+\(?\s*(?:$Compare|$Assignment|$Operators)/;
+
+# check for missing blank lines after declarations
+ if ($sline =~ /^\+\s+\S/ && #Not at char 1
+ # actual declarations
+ $prev_decl && !$sline_decl &&
# indentation of previous and current line are the same
- (($prevline =~ /\+(\s+)\S/) && $sline =~ /^\+$1\S/)) {
+ ($prevline =~ /\+(\s+)\S/ && $sline =~ /^\+$1\S/)) {
if (WARN("LINE_SPACING",
"Missing a blank line after declarations\n" . $hereprev) &&
$fix) {
@@ -3104,6 +3130,22 @@ sub process {
}
}

+# check for reverse christmas tree declarations in net/ and drivers/net/
+ if ($realfile =~ m@^(?:drivers/net/|net/)@ &&
+ $sline =~ /^\+\s+\S/ && #Not at char 1
+ # actual declarations
+ $prev_decl && $sline_decl &&
+ # indentation of previous and current line are the same
+ (($prevline =~ /\+(\s+)\S/) && $sline =~ /^\+$1\S/)) {
+ my $p = get_decl($prevline);
+ my $l = get_decl($sline);
+ if (defined($p) && defined($l) && length($p) < length($l) &&
+ CHK("REVERSE_XMAS_TREE",
+ "Prefer ordering declarations longest to shortest\n" . $hereprev) &&
+ $fix) {
+ }
+ }
+
# check for spaces at the beginning of a line.
# Exceptions:
# 1) within comments