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SubjectRe: [PATCH] Documentation/CodingStyle: Add guidelines for inline assembly
On 02/02/2012 02:33 PM, Josh Triplett wrote:

> Signed-off-by: Josh Triplett <josh@joshtriplett.org>



Applied. Thanks.


> ---
> Documentation/CodingStyle | 29 +++++++++++++++++++++++++++++
> 1 files changed, 29 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
> index 2b90d32..c58b236 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
>



--
~Randy


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