Re: [PATCH 1/4] 24-bit types: typedef and functions for accessing 3-byte arrays as integers

[Boaz Harrosh <bharrosh@panasas.com>]

Chris Leech wrote:
> Both iSCSI and Fibre Channel make use of 24-bit big-endian values in
> frame headers.  This patch defines __be24 and __le24 typedefs for a
> structure wrapped around a 3-byte array, and functions to convert back and
> forth to a 32-bit integer.
> 
> The undefs in iscsi_proto.h are because of the different calling
> convention for the existing hton24 macro in the iSCSI code.  iSCSI will
> be converted in a subsequent patch.
> 
> The undefs in fs/jfs/endian24.h allow JFS to continue using it's own le24
> conversion macros.  JFS is converted to use these types and functions in a
> subsequent patch.
> 
> Change from last posting:
> 
> Moved the 24-bit inline functions to their own header instead of having
> duplicate definitions in linux/byteorder.h and linux/byteorder/generic.h
> 
> Signed-off-by: Chris Leech <christopher.leech@intel.com>
> ---
> 
>  fs/jfs/endian24.h                 |    5 ++++
>  include/linux/byteorder.h         |    9 ++++++++
>  include/linux/byteorder/generic.h |   10 ++++++++
>  include/linux/endian24.h          |   44 +++++++++++++++++++++++++++++++++++++
>  include/linux/types.h             |    2 ++
>  include/scsi/iscsi_proto.h        |    2 ++
>  6 files changed, 72 insertions(+), 0 deletions(-)
>  create mode 100644 include/linux/endian24.h
> 
> 
> diff --git a/fs/jfs/endian24.h b/fs/jfs/endian24.h
> index fa92f7f..45b6397 100644
> --- a/fs/jfs/endian24.h
> +++ b/fs/jfs/endian24.h
> @@ -33,6 +33,9 @@
>  		((__x & (__u32)0x00ff0000UL) >> 16) )); \
>  })
>  
> +#undef __cpu_to_le24
> +#undef __le24_to_cpu
> +

Does #undef also work on inline functions? I didn't know that

>  #if (defined(__KERNEL__) && defined(__LITTLE_ENDIAN)) || (defined(__BYTE_ORDER) && (__BYTE_ORDER == __LITTLE_ENDIAN))
>  	#define __cpu_to_le24(x) ((__u32)(x))
>  	#define __le24_to_cpu(x) ((__u32)(x))
> @@ -42,6 +45,8 @@
>  #endif
>  
>  #ifdef __KERNEL__
> +	#undef cpu_to_le24
> +	#undef le24_to_cpu
>  	#define cpu_to_le24 __cpu_to_le24
>  	#define le24_to_cpu __le24_to_cpu
>  #endif
> diff --git a/include/linux/byteorder.h b/include/linux/byteorder.h
> index 29f002d..2334e3f 100644
> --- a/include/linux/byteorder.h
> +++ b/include/linux/byteorder.h
> @@ -3,6 +3,7 @@
>  
>  #include <linux/types.h>
>  #include <linux/swab.h>
> +#include <linux/endian24.h>
>  
>  #if defined(__LITTLE_ENDIAN) && defined(__BIG_ENDIAN)
>  # error Fix asm/byteorder.h to define one endianness
> @@ -280,15 +281,19 @@ static inline __be64 __cpu_to_be64p(const __u64 *p)
>  #ifdef __KERNEL__
>  
>  # define le16_to_cpu __le16_to_cpu
> +# define le24_to_cpu __le24_to_cpu
>  # define le32_to_cpu __le32_to_cpu
>  # define le64_to_cpu __le64_to_cpu
>  # define be16_to_cpu __be16_to_cpu
> +# define be24_to_cpu __be24_to_cpu
>  # define be32_to_cpu __be32_to_cpu
>  # define be64_to_cpu __be64_to_cpu
>  # define cpu_to_le16 __cpu_to_le16
> +# define cpu_to_le24 __cpu_to_le24
>  # define cpu_to_le32 __cpu_to_le32
>  # define cpu_to_le64 __cpu_to_le64
>  # define cpu_to_be16 __cpu_to_be16
> +# define cpu_to_be24 __cpu_to_be24
>  # define cpu_to_be32 __cpu_to_be32
>  # define cpu_to_be64 __cpu_to_be64
>  
> @@ -332,11 +337,15 @@ static inline __be64 __cpu_to_be64p(const __u64 *p)
>  # define ___htons(x) __cpu_to_be16(x)
>  # define ___ntohl(x) __be32_to_cpu(x)
>  # define ___ntohs(x) __be16_to_cpu(x)
> +# define ___hton24(x) __cpu_to_be24(x)
> +# define ___ntoh24(x) __be24_to_cpu(x)
>  
>  # define htonl(x) ___htonl(x)
>  # define ntohl(x) ___ntohl(x)
>  # define htons(x) ___htons(x)
>  # define ntohs(x) ___ntohs(x)
> +# define hton24(x) ___hton24(x)
> +# define ntoh24(x) ___ntoh24(x)
>  
>  static inline void le16_add_cpu(__le16 *var, u16 val)
>  {
> diff --git a/include/linux/byteorder/generic.h b/include/linux/byteorder/generic.h
> index 0846e6b..87cbec2 100644
> --- a/include/linux/byteorder/generic.h
> +++ b/include/linux/byteorder/generic.h
> @@ -1,6 +1,8 @@
>  #ifndef _LINUX_BYTEORDER_GENERIC_H
>  #define _LINUX_BYTEORDER_GENERIC_H
>  
> +#include <linux/endian24.h>
> +
>  /*
>   * linux/byteorder_generic.h
>   * Generic Byte-reordering support
> @@ -86,12 +88,16 @@
>  #define le64_to_cpu __le64_to_cpu
>  #define cpu_to_le32 __cpu_to_le32
>  #define le32_to_cpu __le32_to_cpu
> +#define cpu_to_le24 __cpu_to_le24
> +#define le24_to_cpu __le24_to_cpu
>  #define cpu_to_le16 __cpu_to_le16
>  #define le16_to_cpu __le16_to_cpu
>  #define cpu_to_be64 __cpu_to_be64
>  #define be64_to_cpu __be64_to_cpu
>  #define cpu_to_be32 __cpu_to_be32
>  #define be32_to_cpu __be32_to_cpu
> +#define cpu_to_be24 __cpu_to_be24
> +#define be24_to_cpu __be24_to_cpu
>  #define cpu_to_be16 __cpu_to_be16
>  #define be16_to_cpu __be16_to_cpu
>  #define cpu_to_le64p __cpu_to_le64p
> @@ -134,11 +140,15 @@
>  #define ___htons(x) __cpu_to_be16(x)
>  #define ___ntohl(x) __be32_to_cpu(x)
>  #define ___ntohs(x) __be16_to_cpu(x)
> +#define ___hton24(x) __cpu_to_be24(x)
> +#define ___ntoh24(x) __be24_to_cpu(x)
>  
>  #define htonl(x) ___htonl(x)
>  #define ntohl(x) ___ntohl(x)
>  #define htons(x) ___htons(x)
>  #define ntohs(x) ___ntohs(x)
> +#define hton24(x) ___hton24(x)
> +#define ntoh24(x) ___ntoh24(x)
>  
>  static inline void le16_add_cpu(__le16 *var, u16 val)
>  {
> diff --git a/include/linux/endian24.h b/include/linux/endian24.h
> new file mode 100644
> index 0000000..beffa57
> --- /dev/null
> +++ b/include/linux/endian24.h
> @@ -0,0 +1,44 @@
> +#ifndef _LINUX_ENDIAN24_H
> +#define _LINUX_ENDIAN24_H
> +
> +#if !defined(_LINUX_BYTEORDER_H) && !defined(_LINUX_BYTEORDER_GENERIC_H)
> +#error "do not include linux/endian24.h directly, use asm/byteorder.h instead"
> +#endif
> +
> +/**
> + * __le24_to_cpu - read a 3-byte array as a 24-bit little-endian integer
> + * @x: __le24, a structure wrapper around a 3-byte array
> + */
> +static __always_inline __u32 __le24_to_cpu(const __le24 x)
> +{
> +	return (__u32) ((x.b[2] << 16) | (x.b[1] << 8) | (x.b[0]));
> +}
> +
> +/**
> + * __cpu_to_le24 - store a value in a 3-byte array in little-endian format
> + * @x: __u32, there is no checking to ensure only the lower 24 bits are set
> + */
> +static __always_inline __le24 __cpu_to_le24(const __u32 x)
> +{
> +	return (__le24) { { x & 0xff, (x >> 8) & 0xff, (x >> 16) & 0xff } };
> +}
> +
> +/**
> + * __be24_to_cpu - read a 3-byte array as a 24-bit big-endian integer
> + * @x: __be24, a structure wrapper around a 3-byte array
> + */
> +static __always_inline __u32 __be24_to_cpu(const __be24 x)
> +{
> +	return (__u32) ((x.b[0] << 16) | (x.b[1] << 8) | (x.b[2]));
> +}
> +
> +/**
> + * __cpu_to_be24 - store a value in a 3-byte array in big-endian format
> + * @x: __u32, there is no checking to ensure only the lower 24 bits are set
> + */
> +static __always_inline __be24 __cpu_to_be24(const __u32 x)
> +{
> +	return (__be24) { { (x >> 16) & 0xff, (x >> 8) & 0xff, x & 0xff } };
> +}
> +
> +#endif /* _LINUX_ENDIAN24_H */
> diff --git a/include/linux/types.h b/include/linux/types.h
> index d4a9ce6..85fcff7 100644
> --- a/include/linux/types.h
> +++ b/include/linux/types.h
> @@ -188,6 +188,8 @@ typedef __u64 __bitwise __be64;
>  typedef __u16 __bitwise __sum16;
>  typedef __u32 __bitwise __wsum;
>  
> +typedef struct { __u8 b[3]; } __be24, __le24;
> +
>  #ifdef __KERNEL__
>  typedef unsigned __bitwise__ gfp_t;
>  
> diff --git a/include/scsi/iscsi_proto.h b/include/scsi/iscsi_proto.h
> index f2a2c11..429c5ff 100644
> --- a/include/scsi/iscsi_proto.h
> +++ b/include/scsi/iscsi_proto.h
> @@ -35,6 +35,8 @@
>  /*
>   * useful common(control and data pathes) macro
>   */
> +#undef ntoh24
> +#undef hton24
>  #define ntoh24(p) (((p)[0] << 16) | ((p)[1] << 8) | ((p)[2]))
>  #define hton24(p, v) { \
>          p[0] = (((v) >> 16) & 0xFF); \
> 

Thanks that looks grate.
Boaz