[dpdk-dev] [PATCH] doc: coding style: use linux kernel style for indentation

[Yuanhan Liu]

Using two tabs for "if" (or "while") statements is a bit weird to me.
Also, using one tab unconditionaly for function definitions and
prototypes doesn't look great.

Here I'd suggest to use the indentation style the Linux kernel
project prefers: to align with the open brace with tabs and
additonal spaces (when necessary).

Example:

  static int
  rte_eal_foo_bar(int a_long_argument_1, int another_long_argument_2,
                  struct foo *yet_another_long_argument_3)

  ret = rte_eal_foo_bar(a_long_argument_1, another_long_argument_2,
                        yet_another_long_argument_3);

  if (really_long_variable_name_1 == really_long_variable_name_2 &&
      var3 == var4) {
          x = y + z;
          ....;
  }

Cc: Thomas Monjalon <thomas.monjalon at 6wind.com>
Cc: Siobhan Butler <siobhan.a.butler at intel.com>
Cc: John McNamara <john.mcnamara at intel.com>
Signed-off-by: Yuanhan Liu <yuanhan.liu at linux.intel.com>
---
 doc/guides/contributing/coding_style.rst | 38 ++++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/doc/guides/contributing/coding_style.rst b/doc/guides/contributing/coding_style.rst
index ad1392d..23cd060 100644
--- a/doc/guides/contributing/coding_style.rst
+++ b/doc/guides/contributing/coding_style.rst
@@ -339,9 +339,11 @@ General
 
 * Do not put any spaces before a tab for indentation.
 * If you have to wrap a long statement, put the operator at the end of the line, and indent again.
-* For control statements (if, while, etc.), continuation it is recommended that the next line be indented by two tabs, rather than one,
-  to prevent confusion as to whether the second line of the control statement forms part of the statement body or not.
-  Alternatively, the line continuation may use additional spaces to line up to an appropriately point on the preceding line, for example, to align to an opening brace.
+* For control statements (if, while, etc.), function definitions and
+  function prototypes continuation lines, it is recommended that the
+  next line be indented by tab and additional spaces when necessary
+  to align to the opening brace. For others, it's also okay to be
+  indented by tab only.
 
 .. note::
 
@@ -350,17 +352,29 @@ General
 .. code-block:: c
 
  while (really_long_variable_name_1 == really_long_variable_name_2 &&
-     var3 == var4){  /* confusing to read as */
-     x = y + z;      /* control stmt body lines up with second line of */
-     a = b + c;      /* control statement itself if single indent used */
+         var3 == var4) { /* confusing to read as */
+         x = y + z;      /* control stmt body lines up with second line of */
+         a = b + c;      /* control statement itself if single indent used */
  }
 
  if (really_long_variable_name_1 == really_long_variable_name_2 &&
-         var3 == var4){  /* two tabs used */
-     x = y + z;          /* statement body no longer lines up */
-     a = b + c;
+     var3 == var4) {            /* align with above opening if statement */
+         x = y + z;             /* statement body no longer lines up */
+         a = b + c;
  }
 
+ /* The continuation line is indented with two tab + 1 space */
+ static int
+ rte_eal_foo_bar(int a_long_argument_1, int another_long_argument_2,
+                 struct foo *yet_another_long_argument_3)
+ {
+        ...
+ }
+
+ /* The continuation line is indented with two tab + 7 spaces */
+ ret = rte_eal_foo_bar(a_long_argument_1, another_long_argument_2,
+                       yet_another_long_argument_3);
+
  z = a + really + long + statement + that + needs +
          two + lines + gets + indented + on + the +
          second + and + subsequent + lines;
@@ -510,9 +524,9 @@ Prototypes
 .. code-block:: c
 
  static char *function1(int _arg, const char *_arg2,
-        struct foo *_arg3,
-        struct bar *_arg4,
-        struct baz *_arg5);
+                        struct foo *_arg3,
+                        struct bar *_arg4,
+                        struct baz *_arg5);
  static void usage(void);
 
 .. note::
-- 
1.9.0