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authorDave Airlie <airlied@redhat.com>2015-04-20 01:32:26 (GMT)
committerDave Airlie <airlied@redhat.com>2015-04-20 03:05:20 (GMT)
commit2c33ce009ca2389dbf0535d0672214d09738e35e (patch)
tree6186a6458c3c160385d794a23eaf07c786a9e61b /Documentation/CodingStyle
parentcec32a47010647e8b0603726ebb75b990a4057a4 (diff)
parent09d51602cf84a1264946711dd4ea0dddbac599a1 (diff)
downloadlinux-2c33ce009ca2389dbf0535d0672214d09738e35e.tar.xz
Merge Linus master into drm-next
The merge is clean, but the arm build fails afterwards, due to API changes in the regulator tree. I've included the patch into the merge to fix the build. Signed-off-by: Dave Airlie <airlied@redhat.com>
Diffstat (limited to 'Documentation/CodingStyle')
-rw-r--r--Documentation/CodingStyle162
1 files changed, 89 insertions, 73 deletions
diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
index 449a8a1..f4b78ea 100644
--- a/Documentation/CodingStyle
+++ b/Documentation/CodingStyle
@@ -13,7 +13,7 @@ and NOT read it. Burn them, it's a great symbolic gesture.
Anyway, here goes:
- Chapter 1: Indentation
+ Chapter 1: Indentation
Tabs are 8 characters, and thus indentations are also 8 characters.
There are heretic movements that try to make indentations 4 (or even 2!)
@@ -56,7 +56,6 @@ instead of "double-indenting" the "case" labels. E.g.:
break;
}
-
Don't put multiple statements on a single line unless you have
something to hide:
@@ -156,25 +155,25 @@ comments on.
Do not unnecessarily use braces where a single statement will do.
-if (condition)
- action();
+ if (condition)
+ action();
and
-if (condition)
- do_this();
-else
- do_that();
+ if (condition)
+ do_this();
+ else
+ do_that();
This does not apply if only one branch of a conditional statement is a single
statement; in the latter case use braces in both branches:
-if (condition) {
- do_this();
- do_that();
-} else {
- otherwise();
-}
+ if (condition) {
+ do_this();
+ do_that();
+ } else {
+ otherwise();
+ }
3.1: Spaces
@@ -186,8 +185,11 @@ although they are not required in the language, as in: "sizeof info" after
"struct fileinfo info;" is declared).
So use a space after these keywords:
+
if, switch, case, for, do, while
+
but not with sizeof, typeof, alignof, or __attribute__. E.g.,
+
s = sizeof(struct file);
Do not add spaces around (inside) parenthesized expressions. This example is
@@ -209,12 +211,15 @@ such as any of these:
= + - < > * / % | & ^ <= >= == != ? :
but no space after unary operators:
+
& * + - ~ ! sizeof typeof alignof __attribute__ defined
no space before the postfix increment & decrement unary operators:
+
++ --
no space after the prefix increment & decrement unary operators:
+
++ --
and no space around the '.' and "->" structure member operators.
@@ -268,13 +273,11 @@ See chapter 6 (Functions).
Chapter 5: Typedefs
Please don't use things like "vps_t".
-
It's a _mistake_ to use typedef for structures and pointers. When you see a
vps_t a;
in the source, what does it mean?
-
In contrast, if it says
struct virtual_container *a;
@@ -372,11 +375,11 @@ In source files, separate functions with one blank line. If the function is
exported, the EXPORT* macro for it should follow immediately after the closing
function brace line. E.g.:
-int system_is_up(void)
-{
- return system_state == SYSTEM_RUNNING;
-}
-EXPORT_SYMBOL(system_is_up);
+ int system_is_up(void)
+ {
+ return system_state == SYSTEM_RUNNING;
+ }
+ EXPORT_SYMBOL(system_is_up);
In function prototypes, include parameter names with their data types.
Although this is not required by the C language, it is preferred in Linux
@@ -405,34 +408,34 @@ The rationale for using gotos is:
modifications are prevented
- saves the compiler work to optimize redundant code away ;)
-int fun(int a)
-{
- int result = 0;
- char *buffer;
-
- buffer = kmalloc(SIZE, GFP_KERNEL);
- if (!buffer)
- return -ENOMEM;
-
- if (condition1) {
- while (loop1) {
- ...
+ int fun(int a)
+ {
+ int result = 0;
+ char *buffer;
+
+ buffer = kmalloc(SIZE, GFP_KERNEL);
+ if (!buffer)
+ return -ENOMEM;
+
+ if (condition1) {
+ while (loop1) {
+ ...
+ }
+ result = 1;
+ goto out_buffer;
}
- result = 1;
- goto out_buffer;
+ ...
+ out_buffer:
+ kfree(buffer);
+ return result;
}
- ...
-out_buffer:
- kfree(buffer);
- return result;
-}
A common type of bug to be aware of it "one err bugs" which look like this:
-err:
- kfree(foo->bar);
- kfree(foo);
- return ret;
+ err:
+ kfree(foo->bar);
+ kfree(foo);
+ return ret;
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_bar:" and "err_foo:".
@@ -503,9 +506,9 @@ values. To do the latter, you can stick the following in your .emacs file:
(defun c-lineup-arglist-tabs-only (ignored)
"Line up argument lists by tabs, not spaces"
(let* ((anchor (c-langelem-pos c-syntactic-element))
- (column (c-langelem-2nd-pos c-syntactic-element))
- (offset (- (1+ column) anchor))
- (steps (floor offset c-basic-offset)))
+ (column (c-langelem-2nd-pos c-syntactic-element))
+ (offset (- (1+ column) anchor))
+ (steps (floor offset c-basic-offset)))
(* (max steps 1)
c-basic-offset)))
@@ -612,7 +615,7 @@ have a reference count on it, you almost certainly have a bug.
Names of macros defining constants and labels in enums are capitalized.
-#define CONSTANT 0x12345
+ #define CONSTANT 0x12345
Enums are preferred when defining several related constants.
@@ -623,28 +626,28 @@ Generally, inline functions are preferable to macros resembling functions.
Macros with multiple statements should be enclosed in a do - while block:
-#define macrofun(a, b, c) \
- do { \
- if (a == 5) \
- do_this(b, c); \
- } while (0)
+ #define macrofun(a, b, c) \
+ do { \
+ if (a == 5) \
+ do_this(b, c); \
+ } while (0)
Things to avoid when using macros:
1) macros that affect control flow:
-#define FOO(x) \
- do { \
- if (blah(x) < 0) \
- return -EBUGGERED; \
- } while(0)
+ #define FOO(x) \
+ do { \
+ if (blah(x) < 0) \
+ return -EBUGGERED; \
+ } while(0)
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:
-#define FOO(val) bar(index, val)
+ #define FOO(val) bar(index, val)
might look like a good thing, but it's confusing as hell when one reads the
code and it's prone to breakage from seemingly innocent changes.
@@ -656,8 +659,21 @@ bite you if somebody e.g. turns FOO into an inline function.
must enclose the expression in parentheses. Beware of similar issues with
macros using parameters.
-#define CONSTANT 0x4000
-#define CONSTEXP (CONSTANT | 3)
+ #define CONSTANT 0x4000
+ #define CONSTEXP (CONSTANT | 3)
+
+5) namespace collisions when defining local variables in macros resembling
+functions:
+
+#define FOO(x) \
+({ \
+ typeof(x) ret; \
+ ret = calc_ret(x); \
+ (ret); \
+)}
+
+ret is a common name for a local variable - __foo_ret is less likely
+to collide with an existing variable.
The cpp manual deals with macros exhaustively. The gcc internals manual also
covers RTL which is used frequently with assembly language in the kernel.
@@ -796,11 +812,11 @@ you should use, rather than explicitly coding some variant of them yourself.
For example, if you need to calculate the length of an array, take advantage
of the macro
- #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+ #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
Similarly, if you need to calculate the size of some structure member, use
- #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
+ #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
There are also min() and max() macros that do strict type checking if you
need them. Feel free to peruse that header file to see what else is already
@@ -813,19 +829,19 @@ Some editors can interpret configuration information embedded in source files,
indicated with special markers. For example, emacs interprets lines marked
like this:
--*- mode: c -*-
+ -*- mode: c -*-
Or like this:
-/*
-Local Variables:
-compile-command: "gcc -DMAGIC_DEBUG_FLAG foo.c"
-End:
-*/
+ /*
+ Local Variables:
+ compile-command: "gcc -DMAGIC_DEBUG_FLAG foo.c"
+ End:
+ */
Vim interprets markers that look like this:
-/* vim:set sw=8 noet */
+ /* vim:set sw=8 noet */
Do not include any of these in source files. People have their own personal
editor configurations, and your source files should not override them. This
@@ -902,9 +918,9 @@ At the end of any non-trivial #if or #ifdef block (more than a few lines),
place a comment after the #endif on the same line, noting the conditional
expression used. For instance:
-#ifdef CONFIG_SOMETHING
-...
-#endif /* CONFIG_SOMETHING */
+ #ifdef CONFIG_SOMETHING
+ ...
+ #endif /* CONFIG_SOMETHING */
Appendix I: References