coding-style: Clarify the expectations around bool

NULL or the ERR_PTR mechanism to report failure.

17) Don't re-invent the kernel macros

17) Using bool

--------------

The Linux kernel bool type is an alias for the C99 _Bool type. bool values can

only evaluate to 0 or 1, and implicit or explicit conversion to bool

automatically converts the value to true or false. When using bool types the

!! construction is not needed, which eliminates a class of bugs.

When working with bool values the true and false definitions should be used

instead of 1 and 0.

bool function return types and stack variables are always fine to use whenever

appropriate. Use of bool is encouraged to improve readability and is often a

better option than 'int' for storing boolean values.

Do not use bool if cache line layout or size of the value matters, as its size

and alignment varies based on the compiled architecture. Structures that are

optimized for alignment and size should not use bool.

If a structure has many true/false values, consider consolidating them into a

bitfield with 1 bit members, or using an appropriate fixed width type, such as

u8.

Similarly for function arguments, many true/false values can be consolidated

into a single bitwise 'flags' argument and 'flags' can often be a more

readable alternative if the call-sites have naked true/false constants.

Otherwise limited use of bool in structures and arguments can improve

readability.

18) Don't re-invent the kernel macros

-------------------------------------

The header file include/linux/kernel.h contains a number of macros that

defined that you shouldn't reproduce in your code.

18) Editor modelines and other cruft

19) Editor modelines and other cruft

------------------------------------

Some editors can interpret configuration information embedded in source files,

work correctly.

19) Inline assembly

20) Inline assembly

-------------------

In architecture-specific code, you may need to use inline assembly to interface

	     : /* outputs */ : /* inputs */ : /* clobbers */);

20) Conditional Compilation

21) Conditional Compilation

---------------------------

Wherever possible, don't use preprocessor conditionals (#if, #ifdef) in .c

			}

		}

# check for bool bitfields

		if ($sline =~ /^.\s+bool\s*$Ident\s*:\s*\d+\s*;/) {

			WARN("BOOL_BITFIELD",

			     "Avoid using bool as bitfield.  Prefer bool bitfields as unsigned int or u<8|16|32>\n" . $herecurr);

		}

# check for bool use in .h files

		if ($realfile =~ /\.h$/ &&

		    $sline =~ /^.\s+bool\s*$Ident\s*(?::\s*d+\s*)?;/) {

			CHK("BOOL_MEMBER",

			    "Avoid using bool structure members because of possible alignment issues - see: https://lkml.org/lkml/2017/11/21/384\n" . $herecurr);

		}

# check for semaphores initialized locked

		if ($line =~ /^.\s*sema_init.+,\W?0\W?\)/) {

			WARN("CONSIDER_COMPLETION",