summaryrefslogtreecommitdiffstats
path: root/Documentation/CodingStyle
diff options
context:
space:
mode:
authorJohn W. Linville <linville@tuxdriver.com>2012-04-12 13:49:28 -0400
committerJohn W. Linville <linville@tuxdriver.com>2012-04-12 13:49:28 -0400
commit8065248069097dddf9945acfb2081025e9618c16 (patch)
treeeddf3fb0372ba0f65c01382d386942ea8d18932d /Documentation/CodingStyle
parente66a8ddff72e85605f2212a0ebc666c7e9116641 (diff)
parentb4838d12e1f3cb48c2489a0b08733b5dbf848297 (diff)
downloadtalos-obmc-linux-8065248069097dddf9945acfb2081025e9618c16.tar.gz
talos-obmc-linux-8065248069097dddf9945acfb2081025e9618c16.zip
Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless
Diffstat (limited to 'Documentation/CodingStyle')
-rw-r--r--Documentation/CodingStyle29
1 files changed, 29 insertions, 0 deletions
diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
index 2b90d328b3ba..c58b236bbe04 100644
--- a/Documentation/CodingStyle
+++ b/Documentation/CodingStyle
@@ -793,6 +793,35 @@ own custom mode, or may have some other magic method for making indentation
work correctly.
+ Chapter 19: Inline assembly
+
+In architecture-specific code, you may need to use inline assembly to interface
+with CPU or platform functionality. Don't hesitate to do so when necessary.
+However, don't use inline assembly gratuitously when C can do the job. You can
+and should poke hardware from C when possible.
+
+Consider writing simple helper functions that wrap common bits of inline
+assembly, rather than repeatedly writing them with slight variations. Remember
+that inline assembly can use C parameters.
+
+Large, non-trivial assembly functions should go in .S files, with corresponding
+C prototypes defined in C header files. The C prototypes for assembly
+functions should use "asmlinkage".
+
+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
+do so, though, and doing so unnecessarily can limit optimization.
+
+When writing a single inline assembly statement containing multiple
+instructions, put each instruction on a separate line in a separate quoted
+string, and end each string except the last with \n\t to properly indent the
+next instruction in the assembly output:
+
+ asm ("magic %reg1, #42\n\t"
+ "more_magic %reg2, %reg3"
+ : /* outputs */ : /* inputs */ : /* clobbers */);
+
+
Appendix I: References
OpenPOWER on IntegriCloud