=========================
This is a short document describing the preferred coding style for the
-linux kernel. Coding style is very personal, and I won't _force_ my
+linux kernel. Coding style is very personal, and I won't **force** my
views on anybody, but this is what goes for anything that I have to be
able to maintain, and I'd prefer it for most other things too. Please
at least consider the points made here.
Heretic people all over the world have claimed that this inconsistency
is ... well ... inconsistent, but all right-thinking people know that
-(a) K&R are _right_ and (b) K&R are right. Besides, functions are
+(a) K&R are **right** and (b) K&R are right. Besides, functions are
special anyway (you can't nest them in C).
-Note that the closing brace is empty on a line of its own, _except_ in
+Note that the closing brace is empty on a line of its own, **except** in
the cases where it is followed by a continuation of the same statement,
ie a ``while`` in a do-statement or an ``else`` in an if-statement, like
this:
global variables are a must. To call a global function ``foo`` is a
shooting offense.
-GLOBAL variables (to be used only if you _really_ need them) need to
+GLOBAL variables (to be used only if you **really** need them) need to
have descriptive names, as do global functions. If you have a function
that counts the number of active users, you should call that
-``count_active_users()`` or similar, you should _not_ call it ``cntusr()``.
+``count_active_users()`` or similar, you should **not** call it ``cntusr()``.
Encoding the type of a function into the name (so-called Hungarian
notation) is brain damaged - the compiler knows the types anyway and can
-----------
Please don't use things like ``vps_t``.
-It's a _mistake_ to use typedef for structures and pointers. When you see a
+It's a **mistake** to use typedef for structures and pointers. When you see a
.. code-block:: c
Lots of people think that typedefs ``help readability``. Not so. They are
useful only for:
- (a) totally opaque objects (where the typedef is actively used to _hide_
+ (a) totally opaque objects (where the typedef is actively used to **hide**
what the object is).
Example: ``pte_t`` etc. opaque objects that you can only access using
NOTE! Opaqueness and ``accessor functions`` are not good in themselves.
The reason we have them for things like pte_t etc. is that there
- really is absolutely _zero_ portably accessible information there.
+ really is absolutely **zero** portably accessible information there.
- (b) Clear integer types, where the abstraction _helps_ avoid confusion
+ (b) Clear integer types, where the abstraction **helps** avoid confusion
whether it is ``int`` or ``long``.
u8/u16/u32 are perfectly fine typedefs, although they fit into
category (d) better than here.
- NOTE! Again - there needs to be a _reason_ for this. If something is
+ NOTE! Again - there needs to be a **reason** for this. If something is
``unsigned long``, then there's no reason to do
typedef unsigned long myflags_t;
might be an ``unsigned int`` and under other configurations might be
``unsigned long``, then by all means go ahead and use a typedef.
- (c) when you use sparse to literally create a _new_ type for
+ (c) when you use sparse to literally create a **new** type for
type-checking.
(d) New types which are identical to standard C99 types, in certain
EVER use a typedef unless you can clearly match one of those rules.
In general, a pointer, or a struct that has elements that can reasonably
-be directly accessed should _never_ be a typedef.
+be directly accessed should **never** be a typedef.
6) Functions
Comments are good, but there is also a danger of over-commenting. NEVER
try to explain HOW your code works in a comment: it's much better to
-write the code so that the _working_ is obvious, and it's a waste of
+write the code so that the **working** is obvious, and it's a waste of
time to explain badly written code.
Generally, you want your comments to tell WHAT your code does, not HOW.
environment they are created and destroyed in should always have
reference counts. In the kernel, garbage collection doesn't exist (and
outside the kernel garbage collection is slow and inefficient), which
-means that you absolutely _have_ to reference count all your uses.
+means that you absolutely **have** to reference count all your uses.
Reference counting means that you can avoid locking, and allows multiple
users to have access to the data structure in parallel - and not having
to worry about the structure suddenly going away from under them just
because they slept or did something else for a while.
-Note that locking is _not_ a replacement for reference counting.
+Note that locking is **not** a replacement for reference counting.
Locking is used to keep data structures coherent, while reference
counting is a memory management technique. Usually both are needed, and
they are not to be confused with each other.
return -EBUGGERED; \
} while (0)
-is a _very_ bad idea. It looks like a function call but exits the ``calling``
+is a **very** bad idea. It looks like a function call but exits the ``calling``
function; don't break the internal parsers of those who will read the code.
2) macros that depend on having a local variable with a magic name:
projects / GitHub / MotorolaMobilityLLC / kernel-slsi.git / commitdiff