modifications are prevented
- saves the compiler work to optimize redundant code away ;)
-int fun(int )
+int fun(int a)
{
int result = 0;
char *buffer = kmalloc(SIZE);
of the function, telling people what it does, and possibly WHY it does
it.
+When commenting the kernel API functions, please use the kerneldoc format.
+See the files Documentation/kernel-doc-nano-HOWTO.txt and scripts/kernel-doc
+for details.
Chapter 8: You've made a mess of it
have a reference count on it, you almost certainly have a bug.
- Chapter 11: Macros, Enums, Inline functions and RTL
+ Chapter 11: Macros, Enums and RTL
Names of macros defining constants and labels in enums are capitalized.
Printing numbers in parentheses (%d) adds no value and should be avoided.
- Chapter 13: References
+ Chapter 13: Allocating memory
+
+The kernel provides the following general purpose memory allocators:
+kmalloc(), kzalloc(), kcalloc(), and vmalloc(). Please refer to the API
+documentation for further information about them.
+
+The preferred form for passing a size of a struct is the following:
+
+ p = kmalloc(sizeof(*p), ...);
+
+The alternative form where struct name is spelled out hurts readability and
+introduces an opportunity for a bug when the pointer variable type is changed
+but the corresponding sizeof that is passed to a memory allocator is not.
+
+Casting the return value which is a void pointer is redundant. The conversion
+from void pointer to any other pointer type is guaranteed by the C programming
+language.
+
+
+ Chapter 14: The inline disease
+
+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
+appropriate (for example as a means of replacing macros, see Chapter 11), it
+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
+icache footprint for the CPU and simply because there is less memory
+available for the pagecache. Just think about it; a pagecache miss causes a
+disk seek, which easily takes 5 miliseconds. There are a LOT of cpu cycles
+that can go into these 5 miliseconds.
+
+A reasonable rule of thumb is to not put inline at functions that have more
+than 3 lines of code in them. An exception to this rule are the cases where
+a parameter is known to be a compiletime constant, and as a result of this
+constantness you *know* the compiler will be able to optimize most of your
+function away at compile time. For a good example of this later case, see
+the kmalloc() inline function.
+
+Often people argue that adding inline to functions that are static and used
+only once is always a win since there is no space tradeoff. While this is
+technically correct, gcc is capable of inlining these automatically without
+help, and the maintenance issue of removing the inline when a second user
+appears outweighs the potential value of the hint that tells gcc to do
+something it would have done anyway.
+
+
+
+ Chapter 15: References
The C Programming Language, Second Edition
by Brian W. Kernighan and Dennis M. Ritchie.
URL: http://cm.bell-labs.com/cm/cs/tpop/
GNU manuals - where in compliance with K&R and this text - for cpp, gcc,
-gcc internals and indent, all available from http://www.gnu.org
+gcc internals and indent, all available from http://www.gnu.org/manual/
WG14 is the international standardization working group for the programming
-language C, URL: http://std.dkuug.dk/JTC1/SC22/WG14/
+language C, URL: http://www.open-std.org/JTC1/SC22/WG14/
+
+Kernel CodingStyle, by greg@kroah.com at OLS 2002:
+http://www.kroah.com/linux/talks/ols_2002_kernel_codingstyle_talk/html/
--
-Last updated on 16 February 2004 by a community effort on LKML.
+Last updated on 30 December 2005 by a community effort on LKML.
git://git.onelab.eu / linux-2.6.git / blobdiff