checkpatch/coding-style: deprecate 80-column warning

Yes, staying withing 80 columns is certainly still _preferred_.  But
it's not the hard limit that the checkpatch warnings imply, and other
concerns can most certainly dominate.

Increase the default limit to 100 characters.  Not because 100
characters is some hard limit either, but that's certainly a "what are
you doing" kind of value and less likely to be about the occasional
slightly longer lines.

Miscellanea:

 - to avoid unnecessary whitespace changes in files, checkpatch will no
   longer emit a warning about line length when scanning files unless
   --strict is also used

 - Add a bit to coding-style about alignment to open parenthesis

Signed-off-by: Joe Perches <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: JoePerches

Documentation/process/coding-style.rst

@@ -84,15 +84,20 @@ Get a decent editor and don't leave whitespace at the end of lines.
 Coding style is all about readability and maintainability using commonly
 available tools.
 
-The limit on the length of lines is 80 columns and this is a strongly
-preferred limit.
-
-Statements longer than 80 columns will be broken into sensible chunks, unless
-exceeding 80 columns significantly increases readability and does not hide
-information. Descendants are always substantially shorter than the parent and
-are placed substantially to the right. The same applies to function headers
-with a long argument list. However, never break user-visible strings such as
-printk messages, because that breaks the ability to grep for them.
+The preferred limit on the length of a single line is 80 columns.
+
+Statements longer than 80 columns should be broken into sensible chunks,
+unless exceeding 80 columns significantly increases readability and does
+not hide information.
+
+Descendants are always substantially shorter than the parent and are
+are placed substantially to the right.  A very commonly used style
+is to align descendants to a function open parenthesis.
+
+These same rules are applied to function headers with a long argument list.
+
+However, never break user-visible strings such as printk messages because
+that breaks the ability to grep for them.
 
 
 3) Placing Braces and Spaces

scripts/checkpatch.pl

@@ -51,7 +51,7 @@
 my @ignore = ();
 my $help = 0;
 my $configuration_file = ".checkpatch.conf";
-my $max_line_length = 80;
+my $max_line_length = 100;
 my $ignore_perl_version = 0;
 my $minimum_perl_version = 5.10.0;
 my $min_conf_desc_length = 4;
@@ -97,9 +97,11 @@ sub help {
   --types TYPE(,TYPE2...)    show only these comma separated message types
   --ignore TYPE(,TYPE2...)   ignore various comma separated message types
   --show-types               show the specific message type in the output
-  --max-line-length=n        set the maximum line length, if exceeded, warn
+  --max-line-length=n        set the maximum line length, (default $max_line_length)
+                             if exceeded, warn on patches
+                             requires --strict for use with --file
   --min-conf-desc-length=n   set the min description length, if shorter, warn
-  --tab-size=n               set the number of spaces for tab (default 8)
+  --tab-size=n               set the number of spaces for tab (default $tabsize)
   --root=PATH                PATH to the kernel tree root
   --no-summary               suppress the per-file summary
   --mailback                 only produce a report in case of warnings/errors
@@ -3240,8 +3242,10 @@ sub process {
 
 			if ($msg_type ne "" &&
 			    (show_type("LONG_LINE") || show_type($msg_type))) {
-				WARN($msg_type,
-				     "line over $max_line_length characters\n" . $herecurr);
+				my $msg_level = \&WARN;
+				$msg_level = \&CHK if ($file);
+				&{$msg_level}($msg_type,
+					      "line length of $length exceeds $max_line_length columns\n" . $herecurr);
 			}
 		}