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Re: [Qemu-trivial] [Qemu-devel] [PATCH 6/6] bswap.h: Document cpu_to_* a


From: Peter Maydell
Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH 6/6] bswap.h: Document cpu_to_* and *_to_cpu conversion functions
Date: Tue, 28 Jun 2016 15:58:51 +0100

On 28 June 2016 at 15:50, Peter Maydell <address@hidden> wrote:
> Add a documentation comment describing the functions for
> converting between the cpu and little or bigendian formats.
>
> Signed-off-by: Peter Maydell <address@hidden>
> ---
>  include/qemu/bswap.h | 58 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 58 insertions(+)
>
> diff --git a/include/qemu/bswap.h b/include/qemu/bswap.h
> index a17d9aa..be3233a 100644
> --- a/include/qemu/bswap.h
> +++ b/include/qemu/bswap.h
> @@ -80,6 +80,64 @@ static inline void bswap64s(uint64_t *s)
>  #define be_bswaps(p, size) do { *p = glue(bswap, size)(*p); } while(0)
>  #endif
>
> +/**
> + * Endianness conversion functions between host cpu and specified endianness.
> + * (We list the complete set of prototypes produced by the macros below
> + * to assist people who search the headers to find their definitions.)
> + *
> + * uint16_t le16_to_cpu(uint16_t v);
> + * uint32_t le32_to_cpu(uint32_t v);
> + * uint64_t le64_to_cpu(uint64_t v);
> + * uint16_t be16_to_cpu(uint16_t v);
> + * uint32_t be32_to_cpu(uint32_t v);
> + * uint64_t be64_to_cpu(uint64_t v);
> + *
> + * Convert the value @v from the specified format to the native
> + * endianness of the host CPU by byteswapping if necessary, and
> + * return the converted value.
> + *
> + * uint16_t cpu_to_le16(uint16_t v);
> + * uint32_t cpu_to_le32(uint32_t v);
> + * uint64_t cpu_to_le64(uint64_t v);
> + * uint16_t cpu_to_be16(uint16_t v);
> + * uint32_t cpu_to_be32(uint32_t v);
> + * uint64_t cpu_to_be64(uint64_t v);
> + *
> + * Convert the value @v from the native endianness of the host CPU to
> + * the specified format by byteswapping if necessary, and return
> + * the converted value.
> + *
> + * uint16_t le16_to_cpus(uint16_t *v);
> + * uint32_t le32_to_cpus(uint32_t *v);
> + * uint64_t le64_to_cpus(uint64_t *v);
> + * uint16_t be16_to_cpus(uint16_t *v);
> + * uint32_t be32_to_cpus(uint32_t *v);
> + * uint64_t be64_to_cpus(uint64_t *v);

Doh. All these prototypes, and the ones in the block below,
should be 'void' return type rather than the integer type.

> + *
> + * Do an in-place conversion of the value pointed to by @v from the
> + * specified format to the native endianness of the host CPU.
> + *
> + * uint16_t cpu_to_le16s(uint16_t *v);
> + * uint32_t cpu_to_le32s(uint32_t *v);
> + * uint64_t cpu_to_le64s(uint64_t *v);
> + * uint16_t cpu_to_be16s(uint16_t *v);
> + * uint32_t cpu_to_be32s(uint32_t *v);
> + * uint64_t cpu_to_be64s(uint64_t *v);
> + *
> + * Do an in-place conversion of the value pointed to by @v from the
> + * native endianness of the host CPU to the specified format.
> + *
> + * Both X_to_cpu() and cpu_to_X() perform the same operation; you
> + * should use whichever one is better documenting of the function your
> + * code is performing.
> + *
> + * Do not use these functions for conversion of values which are in guest
> + * memory, since the data may not be sufficiently aligned for the host CPU's
> + * load and store instructions. Instead you should use the ld*_p() and
> + * st*_p() functions, which perform loads and stores of data of any
> + * required size and endianness and handle possible misalignment.
> + */
> +
>  #define CPU_CONVERT(endian, size, type)\
>  static inline type endian ## size ## _to_cpu(type v)\
>  {\
> --
> 1.9.1
>
>


thanks
-- PMM



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