Commit b1a3459b authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab Committed by Jonathan Corbet

Documentation/CodingStyle: use the proper tag for verbatim font

On Sphinx/ReST notation, ``foo`` means that foo will be will be
marked as inline literal, effectively making it to be presented
as a monospaced font.

As we want this document to be parsed by Sphinx, instead of using
"foo", use ``foo`` for the names that are literal, because it is an
usual typographic convention to use monospaced fonts for functions
and language commands on documents, and we're following such
convention on the other ReST books.
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent d8dbbbc5
...@@ -37,8 +37,8 @@ benefit of warning you when you're nesting your functions too deep. ...@@ -37,8 +37,8 @@ benefit of warning you when you're nesting your functions too deep.
Heed that warning. Heed that warning.
The preferred way to ease multiple indentation levels in a switch statement is The preferred way to ease multiple indentation levels in a switch statement is
to align the "switch" and its subordinate "case" labels in the same column to align the ``switch`` and its subordinate ``case`` labels in the same column
instead of "double-indenting" the "case" labels. E.g.: instead of ``double-indenting`` the ``case`` labels. E.g.:
.. code-block:: c .. code-block:: c
...@@ -141,7 +141,7 @@ special anyway (you can't nest them in C). ...@@ -141,7 +141,7 @@ 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, 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 ie a ``while`` in a do-statement or an ``else`` in an if-statement, like
this: this:
.. code-block:: c .. code-block:: c
...@@ -228,7 +228,7 @@ Do not add spaces around (inside) parenthesized expressions. This example is ...@@ -228,7 +228,7 @@ Do not add spaces around (inside) parenthesized expressions. This example is
s = sizeof( struct file ); s = sizeof( struct file );
When declaring pointer data or a function that returns a pointer type, the When declaring pointer data or a function that returns a pointer type, the
preferred use of '\*' is adjacent to the data name or function name and not preferred use of ``*`` is adjacent to the data name or function name and not
adjacent to the type name. Examples: adjacent to the type name. Examples:
.. code-block:: c .. code-block:: c
...@@ -255,10 +255,10 @@ no space after the prefix increment & decrement unary operators:: ...@@ -255,10 +255,10 @@ no space after the prefix increment & decrement unary operators::
++ -- ++ --
and no space around the '.' and "->" structure member operators. and no space around the ``.`` and ``->`` structure member operators.
Do not leave trailing whitespace at the ends of lines. Some editors with Do not leave trailing whitespace at the ends of lines. Some editors with
"smart" indentation will insert whitespace at the beginning of new lines as ``smart`` indentation will insert whitespace at the beginning of new lines as
appropriate, so you can start typing the next line of code right away. appropriate, so you can start typing the next line of code right away.
However, some such editors do not remove the whitespace if you end up not However, some such editors do not remove the whitespace if you end up not
putting a line of code there, such as if you leave a blank line. As a result, putting a line of code there, such as if you leave a blank line. As a result,
...@@ -276,17 +276,17 @@ context lines. ...@@ -276,17 +276,17 @@ context lines.
C is a Spartan language, and so should your naming be. Unlike Modula-2 C is a Spartan language, and so should your naming be. Unlike Modula-2
and Pascal programmers, C programmers do not use cute names like and Pascal programmers, C programmers do not use cute names like
ThisVariableIsATemporaryCounter. A C programmer would call that ThisVariableIsATemporaryCounter. A C programmer would call that
variable "tmp", which is much easier to write, and not the least more variable ``tmp``, which is much easier to write, and not the least more
difficult to understand. difficult to understand.
HOWEVER, while mixed-case names are frowned upon, descriptive names for HOWEVER, while mixed-case names are frowned upon, descriptive names for
global variables are a must. To call a global function "foo" is a global variables are a must. To call a global function ``foo`` is a
shooting offense. 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 have descriptive names, as do global functions. If you have a function
that counts the number of active users, you should call that 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 Encoding the type of a function into the name (so-called Hungarian
notation) is brain damaged - the compiler knows the types anyway and can notation) is brain damaged - the compiler knows the types anyway and can
...@@ -294,9 +294,9 @@ check those, and it only confuses the programmer. No wonder MicroSoft ...@@ -294,9 +294,9 @@ check those, and it only confuses the programmer. No wonder MicroSoft
makes buggy programs. makes buggy programs.
LOCAL variable names should be short, and to the point. If you have LOCAL variable names should be short, and to the point. If you have
some random integer loop counter, it should probably be called "i". some random integer loop counter, it should probably be called ``i``.
Calling it "loop_counter" is non-productive, if there is no chance of it Calling it ``loop_counter`` is non-productive, if there is no chance of it
being mis-understood. Similarly, "tmp" can be just about any type of being mis-understood. Similarly, ``tmp`` can be just about any type of
variable that is used to hold a temporary value. variable that is used to hold a temporary value.
If you are afraid to mix up your local variable names, you have another If you are afraid to mix up your local variable names, you have another
...@@ -307,7 +307,7 @@ See chapter 6 (Functions). ...@@ -307,7 +307,7 @@ See chapter 6 (Functions).
5) Typedefs 5) Typedefs
----------- -----------
Please don't use things like "vps_t". 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 .. code-block:: c
...@@ -322,35 +322,35 @@ In contrast, if it says ...@@ -322,35 +322,35 @@ In contrast, if it says
struct virtual_container *a; struct virtual_container *a;
you can actually tell what "a" is. you can actually tell what ``a`` is.
Lots of people think that typedefs "help readability". Not so. They are Lots of people think that typedefs ``help readability``. Not so. They are
useful only for: 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). what the object is).
Example: "pte_t" etc. opaque objects that you can only access using Example: ``pte_t`` etc. opaque objects that you can only access using
the proper accessor functions. the proper accessor functions.
NOTE! Opaqueness and "accessor functions" are not good in themselves. NOTE! Opaqueness and ``accessor functions`` are not good in themselves.
The reason we have them for things like pte_t etc. is that there 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". whether it is ``int`` or ``long``.
u8/u16/u32 are perfectly fine typedefs, although they fit into u8/u16/u32 are perfectly fine typedefs, although they fit into
category (d) better than here. 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 ``unsigned long``, then there's no reason to do
typedef unsigned long myflags_t; typedef unsigned long myflags_t;
but if there is a clear reason for why it under certain circumstances but if there is a clear reason for why it under certain circumstances
might be an "unsigned int" and under other configurations might be might be an ``unsigned int`` and under other configurations might be
"unsigned long", then by all means go ahead and use a typedef. ``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. type-checking.
...@@ -359,10 +359,10 @@ useful only for: ...@@ -359,10 +359,10 @@ useful only for:
exceptional circumstances. exceptional circumstances.
Although it would only take a short amount of time for the eyes and Although it would only take a short amount of time for the eyes and
brain to become accustomed to the standard types like 'uint32_t', brain to become accustomed to the standard types like ``uint32_t``,
some people object to their use anyway. some people object to their use anyway.
Therefore, the Linux-specific 'u8/u16/u32/u64' types and their Therefore, the Linux-specific ``u8/u16/u32/u64`` types and their
signed equivalents which are identical to standard types are signed equivalents which are identical to standard types are
permitted -- although they are not mandatory in new code of your permitted -- although they are not mandatory in new code of your
own. own.
...@@ -373,7 +373,7 @@ useful only for: ...@@ -373,7 +373,7 @@ useful only for:
(e) Types safe for use in userspace. (e) Types safe for use in userspace.
In certain structures which are visible to userspace, we cannot In certain structures which are visible to userspace, we cannot
require C99 types and cannot use the 'u32' form above. Thus, we require C99 types and cannot use the ``u32`` form above. Thus, we
use __u32 and similar types in all structures which are shared use __u32 and similar types in all structures which are shared
with userspace. with userspace.
...@@ -440,13 +440,13 @@ locations and some common work such as cleanup has to be done. If there is no ...@@ -440,13 +440,13 @@ locations and some common work such as cleanup has to be done. If there is no
cleanup needed then just return directly. cleanup needed then just return directly.
Choose label names which say what the goto does or why the goto exists. An Choose label names which say what the goto does or why the goto exists. An
example of a good name could be "out_free_buffer:" if the goto frees "buffer". example of a good name could be ``out_free_buffer:`` if the goto frees ``buffer``.
Avoid using GW-BASIC names like "err1:" and "err2:", as you would have to Avoid using GW-BASIC names like ``err1:`` and ``err2:``, as you would have to
renumber them if you ever add or remove exit paths, and they make correctness renumber them if you ever add or remove exit paths, and they make correctness
difficult to verify anyway. difficult to verify anyway.
It is advised to indent labels with a single space (not tab), so that It is advised to indent labels with a single space (not tab), so that
"diff -p" does not confuse labels with functions. ``diff -p`` does not confuse labels with functions.
The rationale for using gotos is: The rationale for using gotos is:
...@@ -480,7 +480,7 @@ The rationale for using gotos is: ...@@ -480,7 +480,7 @@ The rationale for using gotos is:
return result; return result;
} }
A common type of bug to be aware of is "one err bugs" which look like this: A common type of bug to be aware of is ``one err bugs`` which look like this:
.. code-block:: c .. code-block:: c
...@@ -489,9 +489,9 @@ A common type of bug to be aware of is "one err bugs" which look like this: ...@@ -489,9 +489,9 @@ A common type of bug to be aware of is "one err bugs" which look like this:
kfree(foo); kfree(foo);
return ret; return ret;
The bug in this code is that on some exit paths "foo" is NULL. Normally the The bug in this code is that on some exit paths ``foo`` is NULL. Normally the
fix for this is to split it up into two error labels "err_free_bar:" and fix for this is to split it up into two error labels ``err_free_bar:`` and
"err_free_foo:": ``err_free_foo:``:
.. code-block:: c .. code-block:: c
...@@ -560,7 +560,7 @@ item, explaining its use. ...@@ -560,7 +560,7 @@ item, explaining its use.
--------------------------- ---------------------------
That's OK, we all do. You've probably been told by your long-time Unix That's OK, we all do. You've probably been told by your long-time Unix
user helper that "GNU emacs" automatically formats the C sources for user helper that ``GNU emacs`` automatically formats the C sources for
you, and you've noticed that yes, it does do that, but the defaults it you, and you've noticed that yes, it does do that, but the defaults it
uses are less than desirable (in fact, they are worse than random uses are less than desirable (in fact, they are worse than random
typing - an infinite number of monkeys typing into GNU emacs would never typing - an infinite number of monkeys typing into GNU emacs would never
...@@ -605,26 +605,26 @@ This will make emacs go better with the kernel coding style for C ...@@ -605,26 +605,26 @@ This will make emacs go better with the kernel coding style for C
files below ``~/src/linux-trees``. files below ``~/src/linux-trees``.
But even if you fail in getting emacs to do sane formatting, not But even if you fail in getting emacs to do sane formatting, not
everything is lost: use "indent". everything is lost: use ``indent``.
Now, again, GNU indent has the same brain-dead settings that GNU emacs Now, again, GNU indent has the same brain-dead settings that GNU emacs
has, which is why you need to give it a few command line options. has, which is why you need to give it a few command line options.
However, that's not too bad, because even the makers of GNU indent However, that's not too bad, because even the makers of GNU indent
recognize the authority of K&R (the GNU people aren't evil, they are recognize the authority of K&R (the GNU people aren't evil, they are
just severely misguided in this matter), so you just give indent the just severely misguided in this matter), so you just give indent the
options "-kr -i8" (stands for "K&R, 8 character indents"), or use options ``-kr -i8`` (stands for ``K&R, 8 character indents``), or use
"scripts/Lindent", which indents in the latest style. ``scripts/Lindent``, which indents in the latest style.
"indent" has a lot of options, and especially when it comes to comment ``indent`` has a lot of options, and especially when it comes to comment
re-formatting you may want to take a look at the man page. But re-formatting you may want to take a look at the man page. But
remember: "indent" is not a fix for bad programming. remember: ``indent`` is not a fix for bad programming.
10) Kconfig configuration files 10) Kconfig configuration files
------------------------------- -------------------------------
For all of the Kconfig* configuration files throughout the source tree, For all of the Kconfig* configuration files throughout the source tree,
the indentation is somewhat different. Lines under a "config" definition the indentation is somewhat different. Lines under a ``config`` definition
are indented with one tab, while help text is indented an additional two are indented with one tab, while help text is indented an additional two
spaces. Example:: spaces. Example::
...@@ -669,13 +669,13 @@ counting is a memory management technique. Usually both are needed, and ...@@ -669,13 +669,13 @@ counting is a memory management technique. Usually both are needed, and
they are not to be confused with each other. they are not to be confused with each other.
Many data structures can indeed have two levels of reference counting, Many data structures can indeed have two levels of reference counting,
when there are users of different "classes". The subclass count counts when there are users of different ``classes``. The subclass count counts
the number of subclass users, and decrements the global count just once the number of subclass users, and decrements the global count just once
when the subclass count goes to zero. when the subclass count goes to zero.
Examples of this kind of "multi-level-reference-counting" can be found in Examples of this kind of ``multi-level-reference-counting`` can be found in
memory management ("struct mm_struct": mm_users and mm_count), and in memory management (``struct mm_struct``: mm_users and mm_count), and in
filesystem code ("struct super_block": s_count and s_active). filesystem code (``struct super_block``: s_count and s_active).
Remember: if another thread can find your data structure, and you don't Remember: if another thread can find your data structure, and you don't
have a reference count on it, you almost certainly have a bug. have a reference count on it, you almost certainly have a bug.
...@@ -719,7 +719,7 @@ Things to avoid when using macros: ...@@ -719,7 +719,7 @@ Things to avoid when using macros:
return -EBUGGERED; \ return -EBUGGERED; \
} while (0) } 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. 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: 2) macros that depend on having a local variable with a magic name:
...@@ -767,7 +767,7 @@ covers RTL which is used frequently with assembly language in the kernel. ...@@ -767,7 +767,7 @@ covers RTL which is used frequently with assembly language in the kernel.
Kernel developers like to be seen as literate. Do mind the spelling Kernel developers like to be seen as literate. Do mind the spelling
of kernel messages to make a good impression. Do not use crippled of kernel messages to make a good impression. Do not use crippled
words like "dont"; use "do not" or "don't" instead. Make the messages words like ``dont``; use ``do not`` or ``don't`` instead. Make the messages
concise, clear, and unambiguous. concise, clear, and unambiguous.
Kernel messages do not have to be terminated with a period. Kernel messages do not have to be terminated with a period.
...@@ -839,7 +839,7 @@ and return NULL if that occurred. ...@@ -839,7 +839,7 @@ and return NULL if that occurred.
---------------------- ----------------------
There appears to be a common misperception that gcc has a magic "make me There appears to be a common misperception that gcc has a magic "make me
faster" speedup option called "inline". While the use of inlines can be faster" speedup option called ``inline``. While the use of inlines can be
appropriate (for example as a means of replacing macros, see Chapter 12), it appropriate (for example as a means of replacing macros, see Chapter 12), it
very often is not. Abundant use of the inline keyword leads to a much bigger very often is not. Abundant use of the inline keyword leads to a much bigger
kernel, which in turn slows the system as a whole down, due to a bigger kernel, which in turn slows the system as a whole down, due to a bigger
...@@ -869,7 +869,7 @@ something it would have done anyway. ...@@ -869,7 +869,7 @@ something it would have done anyway.
Functions can return values of many different kinds, and one of the Functions can return values of many different kinds, and one of the
most common is a value indicating whether the function succeeded or most common is a value indicating whether the function succeeded or
failed. Such a value can be represented as an error-code integer failed. Such a value can be represented as an error-code integer
(-Exxx = failure, 0 = success) or a "succeeded" boolean (0 = failure, (-Exxx = failure, 0 = success) or a ``succeeded`` boolean (0 = failure,
non-zero = success). non-zero = success).
Mixing up these two sorts of representations is a fertile source of Mixing up these two sorts of representations is a fertile source of
...@@ -882,8 +882,8 @@ convention:: ...@@ -882,8 +882,8 @@ convention::
the function should return an error-code integer. If the name the function should return an error-code integer. If the name
is a predicate, the function should return a "succeeded" boolean. is a predicate, the function should return a "succeeded" boolean.
For example, "add work" is a command, and the add_work() function returns 0 For example, ``add work`` is a command, and the add_work() function returns 0
for success or -EBUSY for failure. In the same way, "PCI device present" is for success or -EBUSY for failure. In the same way, ``PCI device present`` is
a predicate, and the pci_dev_present() function returns 1 if it succeeds in a predicate, and the pci_dev_present() function returns 1 if it succeeds in
finding a matching device or 0 if it doesn't. finding a matching device or 0 if it doesn't.
...@@ -969,7 +969,7 @@ that inline assembly can use C parameters. ...@@ -969,7 +969,7 @@ that inline assembly can use C parameters.
Large, non-trivial assembly functions should go in .S files, with corresponding Large, non-trivial assembly functions should go in .S files, with corresponding
C prototypes defined in C header files. The C prototypes for assembly C prototypes defined in C header files. The C prototypes for assembly
functions should use "asmlinkage". functions should use ``asmlinkage``.
You may need to mark your asm statement as volatile, to prevent GCC from You may need to mark your asm statement as volatile, to prevent GCC from
removing it if GCC doesn't notice any side effects. You don't always need to removing it if GCC doesn't notice any side effects. You don't always need to
......
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