kernel-ark/include/linux/unaligned/generic.h
Harvey Harrison 064106a91b kernel: add common infrastructure for unaligned access
Create a linux/unaligned directory similar in spirit to the linux/byteorder
folder to hold generic implementations collected from various arches.

Currently there are five implementations:
1) packed_struct.h: C-struct based, from asm-generic/unaligned.h
2) le_byteshift.h: Open coded byte-swapping, heavily based on asm-arm
3) be_byteshift.h: Open coded byte-swapping, heavily based on asm-arm
4) memmove.h: taken from multiple implementations in tree
5) access_ok.h: taken from x86 and others, unaligned access is ok.

All of the new implementations checks for sizes not equal to 1,2,4,8
and will fail to link.

API additions:

get_unaligned_{le16|le32|le64|be16|be32|be64}(p) which is meant to replace
code of the form:
le16_to_cpu(get_unaligned((__le16 *)p));

put_unaligned_{le16|le32|le64|be16|be32|be64}(val, pointer) which is meant to
replace code of the form:
put_unaligned(cpu_to_le16(val), (__le16 *)p);

The headers that arches should include from their asm/unaligned.h:

access_ok.h : Wrappers of the byteswapping functions in asm/byteorder

Choose a particular implementation for little-endian access:
le_byteshift.h
le_memmove.h (arch must be LE)
le_struct.h (arch must be LE)

Choose a particular implementation for big-endian access:
be_byteshift.h
be_memmove.h (arch must be BE)
be_struct.h (arch must be BE)

After including as needed from the above, include unaligned/generic.h and
define your arch's get/put_unaligned as (for LE):

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-29 08:06:27 -07:00

69 lines
2.1 KiB
C

#ifndef _LINUX_UNALIGNED_GENERIC_H
#define _LINUX_UNALIGNED_GENERIC_H
/*
* Cause a link-time error if we try an unaligned access other than
* 1,2,4 or 8 bytes long
*/
extern void __bad_unaligned_access_size(void);
#define __get_unaligned_le(ptr) ((__force typeof(*(ptr)))({ \
__builtin_choose_expr(sizeof(*(ptr)) == 1, *(ptr), \
__builtin_choose_expr(sizeof(*(ptr)) == 2, get_unaligned_le16((ptr)), \
__builtin_choose_expr(sizeof(*(ptr)) == 4, get_unaligned_le32((ptr)), \
__builtin_choose_expr(sizeof(*(ptr)) == 8, get_unaligned_le64((ptr)), \
__bad_unaligned_access_size())))); \
}))
#define __get_unaligned_be(ptr) ((__force typeof(*(ptr)))({ \
__builtin_choose_expr(sizeof(*(ptr)) == 1, *(ptr), \
__builtin_choose_expr(sizeof(*(ptr)) == 2, get_unaligned_be16((ptr)), \
__builtin_choose_expr(sizeof(*(ptr)) == 4, get_unaligned_be32((ptr)), \
__builtin_choose_expr(sizeof(*(ptr)) == 8, get_unaligned_be64((ptr)), \
__bad_unaligned_access_size())))); \
}))
#define __put_unaligned_le(val, ptr) ({ \
void *__gu_p = (ptr); \
switch (sizeof(*(ptr))) { \
case 1: \
*(u8 *)__gu_p = (__force u8)(val); \
break; \
case 2: \
put_unaligned_le16((__force u16)(val), __gu_p); \
break; \
case 4: \
put_unaligned_le32((__force u32)(val), __gu_p); \
break; \
case 8: \
put_unaligned_le64((__force u64)(val), __gu_p); \
break; \
default: \
__bad_unaligned_access_size(); \
break; \
} \
(void)0; })
#define __put_unaligned_be(val, ptr) ({ \
void *__gu_p = (ptr); \
switch (sizeof(*(ptr))) { \
case 1: \
*(u8 *)__gu_p = (__force u8)(val); \
break; \
case 2: \
put_unaligned_be16((__force u16)(val), __gu_p); \
break; \
case 4: \
put_unaligned_be32((__force u32)(val), __gu_p); \
break; \
case 8: \
put_unaligned_be64((__force u64)(val), __gu_p); \
break; \
default: \
__bad_unaligned_access_size(); \
break; \
} \
(void)0; })
#endif /* _LINUX_UNALIGNED_GENERIC_H */