linux/bitfield.h: Add primitives for manipulating bitfields both in host- and fixed...

Imports Al Viro's original Linux commit 00b0c9b82663a, which contains
an in depth explanation and two fixes from Johannes Berg:
 e7d4a95da86e0 "bitfield: fix *_encode_bits()",
 37a3862e12382 "bitfield: add u8 helpers".

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
[s.nawrocki: added empty lines between functions and macros]
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
[mb: squash fix including byteorder.h]
Signed-off-by: Matthias Brugger <mbrugger@suse.com>

diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
index 8b9d6ff..7ad02f8 100644 (file)
--- a/include/linux/bitfield.h
+++ b/include/linux/bitfield.h
@@ -16,6 +16,7 @@
 #define _LINUX_BITFIELD_H
 
 #include <linux/bug.h>
+#include <asm/byteorder.h>
 
 /*
  * Bitfield access macros
@@ -103,4 +104,56 @@
                (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
        })
 
+extern void __compiletime_error("value doesn't fit into mask")
+__field_overflow(void);
+extern void __compiletime_error("bad bitfield mask")
+__bad_mask(void);
+
+static __always_inline u64 field_multiplier(u64 field)
+{
+       if ((field | (field - 1)) & ((field | (field - 1)) + 1))
+               __bad_mask();
+       return field & -field;
+}
+
+static __always_inline u64 field_mask(u64 field)
+{
+       return field / field_multiplier(field);
+}
+
+#define ____MAKE_OP(type, base, to, from)                              \
+static __always_inline __##type type##_encode_bits(base v, base field) \
+{                                                                      \
+       if (__builtin_constant_p(v) && (v & ~field_mask(field)))        \
+               __field_overflow();                                     \
+       return to((v & field_mask(field)) * field_multiplier(field));   \
+}                                                                      \
+static __always_inline __##type type##_replace_bits(__##type old,      \
+                                       base val, base field)           \
+{                                                                      \
+       return (old & ~to(field)) | type##_encode_bits(val, field);     \
+}                                                                      \
+static __always_inline void type##p_replace_bits(__##type * p,         \
+                                       base val, base field)           \
+{                                                                      \
+       *p = (*p & ~to(field)) | type##_encode_bits(val, field);        \
+}                                                                      \
+static __always_inline base type##_get_bits(__##type v, base field)    \
+{                                                                      \
+       return (from(v) & field) / field_multiplier(field);             \
+}
+
+#define __MAKE_OP(size)                                                        \
+       ____MAKE_OP(le##size, u##size, cpu_to_le##size, le##size##_to_cpu) \
+       ____MAKE_OP(be##size, u##size, cpu_to_be##size, be##size##_to_cpu) \
+       ____MAKE_OP(u##size, u##size, ,)
+
+____MAKE_OP(u8, u8, ,)
+__MAKE_OP(16)
+__MAKE_OP(32)
+__MAKE_OP(64)
+
+#undef __MAKE_OP
+#undef ____MAKE_OP
+
 #endif