From 8f2df5d369ea57a2c1e4697e508a86fc1346e76f Mon Sep 17 00:00:00 2001 From: Lijun Pan Date: Fri, 20 Jun 2014 12:17:29 -0500 Subject: 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 --- include/linux/compat.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'include') diff --git a/include/linux/compat.h b/include/linux/compat.h index 3fdfb399b50..35e216e06e1 100644 --- a/include/linux/compat.h +++ b/include/linux/compat.h @@ -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 -- cgit v1.2.3