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Commit 9dad92b9 authored by Ivo van Doorn's avatar Ivo van Doorn Committed by John W. Linville
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rt2x00: Calculate register offset during compile time 



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: default avatarGertjan van Wingerde <gwingerde@kpnplanet.nl>
Signed-off-by: default avatarIvo van Doorn <IvDoorn@gmail.com>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent 030352a9

drivers/net/wireless/rt2x00/rt2x00reg.h

+45 −14
Original line number Diff line number Diff line
@@ -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)	\

	};					\

})