Merge tag 'docs-for-linus' of git://git.lwn.net/linux-2.6
Pull documentation updates from Jonathan Corbet: "Numerous fixes, the overdue removal of the i2o docs, some new Chinese translations, and, hopefully, the README fix that will end the flow of identical patches to that file" * tag 'docs-for-linus' of git://git.lwn.net/linux-2.6: (34 commits) Documentation/memcg: update memcg/kmem status Documentation: blackfin: Makefile: Typo building issue Documentation/vm/pagemap.txt: correct location of page-types tool Documentation/memory-barriers.txt: typo fix doc: Add guest_nice column to example output of `cat /proc/stat' Documentation/kernel-parameters: Move "eagerfpu" to its right place Documentation: gpio: Update ACPI part of the document to mention _DSD docs/completion.txt: Various tweaks and corrections doc: completion: context, scope and language fixes Documentation:Update Documentation/zh_CN/arm64/memory.txt Documentation:Update Documentation/zh_CN/arm64/booting.txt Documentation: Chinese translation of arm64/legacy_instructions.txt DocBook media: fix broken EIA hyperlink Documentation: tweak the maintainers entry README: Change gzip/bzip2 to xz compression format README: Update version number reference doc:pci: Fix typo in Documentation/PCI Documentation: drm: Use '->' when describing access through pointers. Documentation: Remove mentioning of block barriers Documentation/email-clients.txt: Fix one grammar mistake, add extra info about TB ...
This commit is contained in:
Linus Torvalds
@@ -13,7 +13,7 @@ and NOT read it. Burn them, it's a great symbolic gesture.
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Anyway, here goes:
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Chapter 1: Indentation
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Chapter 1: Indentation
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Tabs are 8 characters, and thus indentations are also 8 characters.
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There are heretic movements that try to make indentations 4 (or even 2!)
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@@ -56,7 +56,6 @@ instead of "double-indenting" the "case" labels. E.g.:
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break;
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}
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Don't put multiple statements on a single line unless you have
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something to hide:
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@@ -156,25 +155,25 @@ comments on.
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Do not unnecessarily use braces where a single statement will do.
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if (condition)
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action();
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if (condition)
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action();
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and
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if (condition)
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do_this();
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else
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do_that();
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if (condition)
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do_this();
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else
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do_that();
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This does not apply if only one branch of a conditional statement is a single
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statement; in the latter case use braces in both branches:
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if (condition) {
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do_this();
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do_that();
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} else {
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otherwise();
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}
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if (condition) {
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do_this();
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do_that();
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} else {
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otherwise();
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}
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3.1: Spaces
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@@ -186,8 +185,11 @@ although they are not required in the language, as in: "sizeof info" after
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"struct fileinfo info;" is declared).
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So use a space after these keywords:
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if, switch, case, for, do, while
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but not with sizeof, typeof, alignof, or __attribute__. E.g.,
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s = sizeof(struct file);
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Do not add spaces around (inside) parenthesized expressions. This example is
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@@ -209,12 +211,15 @@ such as any of these:
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= + - < > * / % | & ^ <= >= == != ? :
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but no space after unary operators:
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& * + - ~ ! sizeof typeof alignof __attribute__ defined
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no space before the postfix increment & decrement unary operators:
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++ --
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no space after the prefix increment & decrement unary operators:
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++ --
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and no space around the '.' and "->" structure member operators.
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@@ -268,13 +273,11 @@ See chapter 6 (Functions).
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Chapter 5: Typedefs
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Please don't use things like "vps_t".
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It's a _mistake_ to use typedef for structures and pointers. When you see a
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vps_t a;
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in the source, what does it mean?
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In contrast, if it says
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struct virtual_container *a;
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@@ -372,11 +375,11 @@ In source files, separate functions with one blank line. If the function is
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exported, the EXPORT* macro for it should follow immediately after the closing
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function brace line. E.g.:
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int system_is_up(void)
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{
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return system_state == SYSTEM_RUNNING;
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}
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EXPORT_SYMBOL(system_is_up);
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int system_is_up(void)
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{
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return system_state == SYSTEM_RUNNING;
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}
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EXPORT_SYMBOL(system_is_up);
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In function prototypes, include parameter names with their data types.
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Although this is not required by the C language, it is preferred in Linux
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@@ -405,34 +408,34 @@ The rationale for using gotos is:
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modifications are prevented
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- saves the compiler work to optimize redundant code away ;)
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int fun(int a)
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{
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int result = 0;
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char *buffer;
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int fun(int a)
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{
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int result = 0;
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char *buffer;
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buffer = kmalloc(SIZE, GFP_KERNEL);
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if (!buffer)
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return -ENOMEM;
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buffer = kmalloc(SIZE, GFP_KERNEL);
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if (!buffer)
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return -ENOMEM;
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if (condition1) {
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while (loop1) {
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...
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if (condition1) {
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while (loop1) {
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...
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}
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result = 1;
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goto out_buffer;
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}
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result = 1;
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goto out_buffer;
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...
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out_buffer:
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kfree(buffer);
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return result;
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}
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...
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out_buffer:
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kfree(buffer);
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return result;
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}
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A common type of bug to be aware of it "one err bugs" which look like this:
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err:
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kfree(foo->bar);
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kfree(foo);
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return ret;
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err:
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kfree(foo->bar);
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kfree(foo);
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return ret;
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The bug in this code is that on some exit paths "foo" is NULL. Normally the
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fix for this is to split it up into two error labels "err_bar:" and "err_foo:".
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@@ -503,9 +506,9 @@ values. To do the latter, you can stick the following in your .emacs file:
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(defun c-lineup-arglist-tabs-only (ignored)
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"Line up argument lists by tabs, not spaces"
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(let* ((anchor (c-langelem-pos c-syntactic-element))
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(column (c-langelem-2nd-pos c-syntactic-element))
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(offset (- (1+ column) anchor))
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(steps (floor offset c-basic-offset)))
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(column (c-langelem-2nd-pos c-syntactic-element))
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(offset (- (1+ column) anchor))
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(steps (floor offset c-basic-offset)))
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(* (max steps 1)
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c-basic-offset)))
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@@ -612,7 +615,7 @@ have a reference count on it, you almost certainly have a bug.
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Names of macros defining constants and labels in enums are capitalized.
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#define CONSTANT 0x12345
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#define CONSTANT 0x12345
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Enums are preferred when defining several related constants.
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@@ -623,28 +626,28 @@ Generally, inline functions are preferable to macros resembling functions.
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Macros with multiple statements should be enclosed in a do - while block:
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#define macrofun(a, b, c) \
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do { \
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if (a == 5) \
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do_this(b, c); \
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} while (0)
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#define macrofun(a, b, c) \
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do { \
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if (a == 5) \
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do_this(b, c); \
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} while (0)
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Things to avoid when using macros:
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1) macros that affect control flow:
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#define FOO(x) \
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do { \
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if (blah(x) < 0) \
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return -EBUGGERED; \
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} while(0)
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#define FOO(x) \
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do { \
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if (blah(x) < 0) \
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return -EBUGGERED; \
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} while(0)
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is a _very_ bad idea. It looks like a function call but exits the "calling"
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function; don't break the internal parsers of those who will read the code.
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2) macros that depend on having a local variable with a magic name:
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#define FOO(val) bar(index, val)
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#define FOO(val) bar(index, val)
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might look like a good thing, but it's confusing as hell when one reads the
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code and it's prone to breakage from seemingly innocent changes.
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@@ -656,8 +659,8 @@ bite you if somebody e.g. turns FOO into an inline function.
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must enclose the expression in parentheses. Beware of similar issues with
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macros using parameters.
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#define CONSTANT 0x4000
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#define CONSTEXP (CONSTANT | 3)
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#define CONSTANT 0x4000
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#define CONSTEXP (CONSTANT | 3)
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5) namespace collisions when defining local variables in macros resembling
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functions:
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@@ -809,11 +812,11 @@ you should use, rather than explicitly coding some variant of them yourself.
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For example, if you need to calculate the length of an array, take advantage
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of the macro
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#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
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#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
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Similarly, if you need to calculate the size of some structure member, use
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#define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
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#define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
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There are also min() and max() macros that do strict type checking if you
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need them. Feel free to peruse that header file to see what else is already
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@@ -826,19 +829,19 @@ Some editors can interpret configuration information embedded in source files,
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indicated with special markers. For example, emacs interprets lines marked
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like this:
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-*- mode: c -*-
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-*- mode: c -*-
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Or like this:
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/*
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Local Variables:
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compile-command: "gcc -DMAGIC_DEBUG_FLAG foo.c"
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End:
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*/
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/*
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Local Variables:
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compile-command: "gcc -DMAGIC_DEBUG_FLAG foo.c"
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End:
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*/
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Vim interprets markers that look like this:
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/* vim:set sw=8 noet */
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/* vim:set sw=8 noet */
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Do not include any of these in source files. People have their own personal
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editor configurations, and your source files should not override them. This
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@@ -915,9 +918,9 @@ At the end of any non-trivial #if or #ifdef block (more than a few lines),
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place a comment after the #endif on the same line, noting the conditional
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expression used. For instance:
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#ifdef CONFIG_SOMETHING
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...
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#endif /* CONFIG_SOMETHING */
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#ifdef CONFIG_SOMETHING
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...
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#endif /* CONFIG_SOMETHING */
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Appendix I: References
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Reference in New Issue
Block a user