CODING-STYLE

   1 Every project has its coding style, and kmod is not an exception. This
   2 document describes the preferred coding style for kmod code, in order to keep
   3 some level of consistency among developers so that code can be easily
   4 understood and maintained, and also to help your code survive under
   5 maintainer's fastidious eyes so that you can get a passport for your patch
   6 ASAP.
   7
   8 First of all, kmod coding style must follow every rule for Linux kernel
   9 (http://www.kernel.org/doc/Documentation/CodingStyle). There also exists a tool
  10 named checkpatch.pl to help you check the compliance with it. Just type
  11 "checkpatch.pl --no-tree patch_name" to check your patch. In theory, you need
  12 to clean up all the warnings and errors except this one: "ERROR: Missing
  13 Signed-off-by: line(s)". kmod does not used Signed-Off lines, so including
  14 them is actually an error.  In certain circumstances one can ignore the 80
  15 character per line limit.  This is generally only allowed if the alternative
  16 would make the code even less readable.
  17
  18 Besides the kernel coding style above, kmod coding style is heavily based on
  19 oFono's and BlueZ's. Below some basic rules:
  20
  21 1) Wrap line at 80 char limit.
  22
  23 There are a few exceptions:
  24         - Headers may or may not wrap
  25         - If it's a string that is hitting the limit, it's preferred not to break
  26           in order to be able to grep for that string. E.g:
  27
  28                 err = my_function(ctx, "this is a long string that will pass the 80chr limit");
  29
  30         - If code would become unreadable if line is wrapped
  31         - If there's only one argument to the function, don't put it alone in a
  32           new line.
  33
  34 Align the wrapped line either with tabs (BlueZ, oFono, etc) or tab + spaces
  35 (kernel), at your discretion. Kernel's is preferred.
  36
  37 2) It's better to return/exit early in a function than having a really long
  38    "if (...) { }". Example:
  39
  40    if (x) {     // worse        |       if (!x)                 // better
  41            ...                  |               return b;
  42            ...                  |
  43            ...                  |       ...
  44            ...                  |       ...
  45            ...                  |       ...
  46            ...                  |       ...
  47            ...                  |       ...
  48            ...                  |       ...
  49    } else {                     |       ...
  50            return b;            |       return a;
  51    }                            |
  52                                 |
  53    return a;                    |
  54
  55 3) Don't initialize variable unnecessarily
  56 When declaring a variable, try not to initialize it unless necessary.
  57
  58 Example:
  59 int i = 1;  // wrong
  60
  61 for (i = 0; i < 3; i++) {
  62 }
  63
  64 4) Let the includes in the following order, separated by a new line:
  65         < system headers >
  66         < shared/* >
  67         < libkmod >
  68         < tool >
  69         "local headers"