xref: /aosp_15_r20/external/kmod/CODING-STYLE (revision cc4ad7da8cefe208cb129ac2aa9a357c7c72deb2)

Every project has its coding style, and kmod is not an exception. This
document describes the preferred coding style for kmod code, in order to keep
some level of consistency among developers so that code can be easily
understood and maintained, and also to help your code survive under
maintainer's fastidious eyes so that you can get a passport for your patch
ASAP.

First of all, kmod coding style must follow every rule for Linux kernel
(http://www.kernel.org/doc/Documentation/CodingStyle). There also exists a tool
named checkpatch.pl to help you check the compliance with it. Just type
"checkpatch.pl --no-tree patch_name" to check your patch. In theory, you need
to clean up all the warnings and errors except this one: "ERROR: Missing
Signed-off-by: line(s)". kmod does not used Signed-Off lines, so including
them is actually an error.  In certain circumstances one can ignore the 80
character per line limit.  This is generally only allowed if the alternative
would make the code even less readable.

Besides the kernel coding style above, kmod coding style is heavily based on
oFono's and BlueZ's. Below some basic rules:

1) Wrap line at 80 char limit.

There are a few exceptions:
	- Headers may or may not wrap
	- If it's a string that is hitting the limit, it's preferred not to break
	  in order to be able to grep for that string. E.g:

		err = my_function(ctx, "this is a long string that will pass the 80chr limit");

	- If code would become unreadable if line is wrapped
	- If there's only one argument to the function, don't put it alone in a
	  new line.

Align the wrapped line either with tabs (BlueZ, oFono, etc) or tab + spaces
(kernel), at your discretion. Kernel's is preferred.

2) It's better to return/exit early in a function than having a really long
   "if (...) { }". Example:

   if (x) {	// worse	|	if (!x)			// better
	   ...			|		return b;
	   ...			|
	   ...			|	...
	   ...			|	...
	   ...			|	...
	   ...			|	...
	   ...			|	...
	   ...			|	...
   } else {			|	...
	   return b;		|	return a;
   }				|
				|
   return a;			|

3) Don't initialize variable unnecessarily
When declaring a variable, try not to initialize it unless necessary.

Example:
int i = 1;  // wrong

for (i = 0; i < 3; i++) {
}

4) Let the includes in the following order, separated by a new line:
	< system headers >
	< shared/* >
	< libkmod >
	< tool >
	"local headers"