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author | Jiri Kosina <jkosina@suse.cz> | 2012-04-08 23:48:52 +0400 |
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committer | Jiri Kosina <jkosina@suse.cz> | 2012-04-08 23:48:52 +0400 |
commit | e75d660672ddd11704b7f0fdb8ff21968587b266 (patch) | |
tree | ccb9c107744c10b553c0373e450bee3971d16c00 /Documentation/CodingStyle | |
parent | 61282f37927143e45b03153f3e7b48d6b702147a (diff) | |
parent | 0034102808e0dbbf3a2394b82b1bb40b5778de9e (diff) | |
download | linux-e75d660672ddd11704b7f0fdb8ff21968587b266.tar.xz |
Merge branch 'master' into for-next
Merge with latest Linus' tree, as I have incoming patches
that fix code that is newer than current HEAD of for-next.
Conflicts:
drivers/net/ethernet/realtek/r8169.c
Diffstat (limited to 'Documentation/CodingStyle')
-rw-r--r-- | Documentation/CodingStyle | 29 |
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 |