By using __ffs() the register offsets were always calculated
at run-time which all FIELD32/FIELD16 definitions were builtin
constants. This means we can heavily optimize the register handling
by allowing GCC to do all the work during compilation.
Add some compile_ffs() macros to perform the calculation at
compile time. After this each rt2x00 module size is reduced
by ~2500 bytes. And the stack size of several functions is reduced
as well which further limits the number of rt2x00 results in
'make checkstack'.
v2: Merge GertJan's bugfix of patch [1/11] directly into this patch
instead of providing it as seperate patch.
v3: Add extra parentheses when bitshifting __x
Signed-off-by: Gertjan van Wingerde <gwingerde@xxxxxxxxxxxx>
Signed-off-by: Ivo van Doorn <IvDoorn@xxxxxxxxx>
---
John, this patch is a combination of patch [1/11] and [2/11] so please
either apply those 2 patches or just this single patch to get the correct result :)
---
diff --git a/drivers/net/wireless/rt2x00/rt2x00reg.h b/drivers/net/wireless/rt2x00/rt2x00reg.h
index 3f255df..7999d54 100644
--- a/drivers/net/wireless/rt2x00/rt2x00reg.h
+++ b/drivers/net/wireless/rt2x00/rt2x00reg.h
@@ -130,40 +130,71 @@ struct rt2x00_field32 {
/*
* Power of two check, this will check
- * if the mask that has been given contains
- * and contiguous set of bits.
+ * if the mask that has been given contains and contiguous set of bits.
+ * Note that we cannot use the is_power_of_2() function since this
+ * check must be done at compile-time.
*/
#define is_power_of_two(x) ( !((x) & ((x)-1)) )
#define low_bit_mask(x) ( ((x)-1) & ~(x) )
#define is_valid_mask(x) is_power_of_two(1 + (x) + low_bit_mask(x))
+/*
+ * Macro's to find first set bit in a variable.
+ * These macro's behaves the same as the __ffs() function with
+ * the most important difference that this is done during
+ * compile-time rather then run-time.
+ */
+#define compile_ffs2(__x) \
+ ( ((__x) & 0x1) ? 0 : 1 )
+
+#define compile_ffs4(__x) \
+ ( ((__x) & 0x3) ? \
+ compile_ffs2(__x) : (compile_ffs2((__x) >> 2) + 2) )
+
+#define compile_ffs8(__x) \
+ ( ((__x) & 0xf) ? \
+ compile_ffs4(__x) : (compile_ffs4((__x) >> 4) + 4) )
+
+#define compile_ffs16(__x) \
+ ( ((__x) & 0xff) ? \
+ compile_ffs8(__x) : (compile_ffs8((__x) >> 8) + 8) )
+
+#define compile_ffs32(__x) \
+ ( ((__x) & 0xffff) ? \
+ compile_ffs16(__x) : (compile_ffs16((__x) >> 16) + 16) )
+
+/*
+ * This macro will check the requirements for the FIELD{8,16,32} macros
+ * The mask should be a constant non-zero contiguous set of bits which
+ * does not exceed the given typelimit.
+ */
+#define FIELD_CHECK(__mask, __type) \
+ BUILD_BUG_ON(!__builtin_constant_p(__mask) || \
+ !(__mask) || \
+ !is_valid_mask(__mask) || \
+ (__mask) != (__type)(__mask)) \
+
#define FIELD8(__mask) \
({ \
- BUILD_BUG_ON(!(__mask) || \
- !is_valid_mask(__mask) || \
- (__mask) != (u8)(__mask)); \
+ FIELD_CHECK(__mask, u8); \
(struct rt2x00_field8) { \
- __ffs(__mask), (__mask) \
+ compile_ffs8(__mask), (__mask) \
}; \
})
#define FIELD16(__mask) \
({ \
- BUILD_BUG_ON(!(__mask) || \
- !is_valid_mask(__mask) || \
- (__mask) != (u16)(__mask));\
+ FIELD_CHECK(__mask, u16); \
(struct rt2x00_field16) { \
- __ffs(__mask), (__mask) \
+ compile_ffs16(__mask), (__mask) \
}; \
})
#define FIELD32(__mask) \
({ \
- BUILD_BUG_ON(!(__mask) || \
- !is_valid_mask(__mask) || \
- (__mask) != (u32)(__mask));\
+ FIELD_CHECK(__mask, u32); \
(struct rt2x00_field32) { \
- __ffs(__mask), (__mask) \
+ compile_ffs32(__mask), (__mask) \
}; \
})
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