linux/compat.h: port lower_32_bits and upper_32_bits from Linux

[backport from linux commit 204b885e and 218e180e7]
64 bit processors are becomming more and more popular.
lower_32_bits and upper_32_bits save our labor doing
shifts/manipulations like (u32)(n) and (u32)((n) >> 32).
They are good helpers in both little and big endian cases.
Port these two functions here from Linux:include/linux/kernel.h,
cater the comment message to little/big endian cases.
Later on, developers could include linux/compat.h if they want to
use these two functions.

Signed-off-by: Lijun Pan <Lijun.Pan@freescale.com>
This commit is contained in:
Lijun Pan 2014-06-20 12:17:29 -05:00 committed by Tom Rini
parent 9d78b9ae8d
commit 8f2df5d369

View File

@ -57,4 +57,23 @@
, __FILE__, __LINE__); }
#define PAGE_SIZE 4096
/**
* upper_32_bits - return MSB bits 32-63 of a number if little endian, or
* return MSB bits 0-31 of a number if big endian.
* @n: the number we're accessing
*
* A basic shift-right of a 64- or 32-bit quantity. Use this to suppress
* the "right shift count >= width of type" warning when that quantity is
* 32-bits.
*/
#define upper_32_bits(n) ((u32)(((n) >> 16) >> 16))
/**
* lower_32_bits - return LSB bits 0-31 of a number if little endian, or
* return LSB bits 32-63 of a number if big endian.
* @n: the number we're accessing
*/
#define lower_32_bits(n) ((u32)(n))
#endif