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    Subject[PATCH 1/4] 24-bit types: typedef and functions for accessing 3-byte arrays as integers
    Date
    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
    +
    #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); \


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