Re: [PATCH v5 03/16] xen: Implement common byte{order,swap}.h

[Jan Beulich <jbeulich@xxxxxxxx>]

On 28.03.2025 14:44, Andrew Cooper wrote:
> From: Lin Liu <lin.liu@xxxxxxxxxx>
> 
> The current swab??() infrastructure is unecesserily complicated, and can be
> repated entirely with compiler builtins.
> 
> All supported compilers provide __BYTE_ORDER__ and __builtin_bswap??().
> 
> Nothing in Xen cares about the values of __{BIG,LITTLE}_ENDIAN; just that one
> of them is defined.  Therefore, centralise their definitions in xen/config.h

And even if we cared somewhere, __ORDER_{BIG,LITTLE}_ENDIAN__ supply them
just fine.

> Signed-off-by: Lin Liu <lin.liu@xxxxxxxxxx>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
with two nits taken care of:

> --- /dev/null
> +++ b/xen/include/xen/byteorder.h
> @@ -0,0 +1,44 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef XEN_BYTEORDER_H
> +#define XEN_BYTEORDER_H
> +
> +#include <xen/byteswap.h>
> +#include <xen/types.h>

It's stdint.h that's needed here, not types.h?

> +#if defined(__LITTLE_ENDIAN)
> +
> +# define cpu_to_le64(x) (uint64_t)(x)
> +# define le64_to_cpu(x) (uint64_t)(x)
> +# define cpu_to_le32(x) (uint32_t)(x)
> +# define le32_to_cpu(x) (uint32_t)(x)
> +# define cpu_to_le16(x) (uint16_t)(x)
> +# define le16_to_cpu(x) (uint16_t)(x)

(Not just) for Misra these all need another pair of parentheses around the
entire expressions.

> +# define cpu_to_be64(x) bswap64(x)
> +# define be64_to_cpu(x) bswap64(x)
> +# define cpu_to_be32(x) bswap32(x)
> +# define be32_to_cpu(x) bswap32(x)
> +# define cpu_to_be16(x) bswap16(x)
> +# define be16_to_cpu(x) bswap16(x)
> +
> +#elif defined(__BIG_ENDIAN)
> +
> +# define cpu_to_le64(x) bswap64(x)
> +# define le64_to_cpu(x) bswap64(x)
> +# define cpu_to_le32(x) bswap32(x)
> +# define le32_to_cpu(x) bswap32(x)
> +# define cpu_to_le16(x) bswap16(x)
> +# define le16_to_cpu(x) bswap16(x)
> +
> +# define cpu_to_be64(x) (uint64_t)(x)
> +# define be64_to_cpu(x) (uint64_t)(x)
> +# define cpu_to_be32(x) (uint32_t)(x)
> +# define be32_to_cpu(x) (uint32_t)(x)
> +# define cpu_to_be16(x) (uint16_t)(x)
> +# define be16_to_cpu(x) (uint16_t)(x)

Same here, even if Eclair likely wouldn't spot this right now.

Jan