[PATCH 1/3] 24-bit types: typedef and macros for accessing 3-bytearrays as integers

[Chris Leech]

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 macros 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.

Signed-off-by: Chris Leech <christopher.leech@xxxxxxxxx>
---

 include/linux/byteorder.h         |   56 ++++++++++++++++++++++++++++++++++++
 include/linux/byteorder/generic.h |   57 +++++++++++++++++++++++++++++++++++++
 include/linux/types.h             |    2 +
 include/scsi/iscsi_proto.h        |    2 +
 4 files changed, 117 insertions(+), 0 deletions(-)


diff --git a/include/linux/byteorder.h b/include/linux/byteorder.h
index 29f002d..e41c17b 100644
--- a/include/linux/byteorder.h
+++ b/include/linux/byteorder.h
@@ -62,6 +62,54 @@
 # define __cpu_to_le64(x) ((__force __le64)__swab64(x))
 #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
+ *
+ * Evaluates to a __u32 integer type
+ */
+#define __le24_to_cpu(x) \
+({ \
+	__le24 _x = (x); \
+	(__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
+ *
+ * Evaluates to an __le24 compound literal
+ */
+#define __cpu_to_le24(x) \
+({ \
+	__u32 _x = (x); \
+	(__le24) { .b = { _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
+ *
+ * Evaluates to a __u32 integer type
+ */
+#define __be24_to_cpu(x) \
+({ \
+	__be24 _x = (x); \
+	(__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
+ *
+ * Evaluates to an __be24 compound literal
+ */
+#define __cpu_to_be24(x) \
+({ \
+	__u32 _x = (x); \
+	(__be24) { .b = { (_x >> 16) & 0xff, (_x >> 8) & 0xff, _x & 0xff } }; \
+})
+
 /*
  * These helpers could be phased out over time as the base version
  * handles constant folding.
@@ -280,15 +328,19 @@ 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 +384,15 @@ 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..a57fbc3 100644
--- a/include/linux/byteorder/generic.h
+++ b/include/linux/byteorder/generic.h
@@ -119,6 +119,59 @@
 #define cpu_to_be16s __cpu_to_be16s
 #define be16_to_cpus __be16_to_cpus
 
+/**
+ * __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
+ *
+ * Evaluates to a __u32 integer type
+ */
+#define __le24_to_cpu(x) \
+({ \
+	__le24 _x = (x); \
+	(__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
+ *
+ * Evaluates to an __le24 compound literal
+ */
+#define __cpu_to_le24(x) \
+({ \
+	__u32 _x = (x); \
+	(__le24) { .b = { _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
+ *
+ * Evaluates to a __u32 integer type
+ */
+#define __be24_to_cpu(x) \
+({ \
+	__be24 _x = (x); \
+	(__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
+ *
+ * Evaluates to an __be24 compound literal
+ */
+#define __cpu_to_be24(x) \
+({ \
+	__u32 _x = (x); \
+	(__be24) { .b = { (_x >> 16) & 0xff, (_x >> 8) & 0xff, _x & 0xff } }; \
+})
+
+#define le24_to_cpu __le24_to_cpu
+#define cpu_to_le24 __cpu_to_le24
+#define be24_to_cpu __be24_to_cpu
+#define cpu_to_be24 __cpu_to_be24
+
 /*
  * They have to be macros in order to do the constant folding
  * correctly - if the argument passed into a inline function
@@ -134,11 +187,15 @@
 #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/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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