From 218e180e7ea5334e1f94121940ba82cd1f0f4e58 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Thu, 10 May 2007 03:15:18 -0700 Subject: add upper-32-bits macro We keep on getting "right shift count >= width of type" warnings when doing things like sector_t s; x = s >> 56; because with CONFIG_LBD=n, s is only 32-bit. Similar problems can occur with dma_addr_t's. So add a simple wrapper function which code can use to avoid this warning. The above example would become x = upper_32_bits(s) >> 24; The first user is in fact AFS. Cc: James Bottomley Cc: "Cameron, Steve" Cc: "Miller, Mike (OS Dev)" Cc: Hisashi Hifumi Cc: Alan Cox Cc: David Howells Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 144b615f3a8..8645181fca0 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -41,6 +41,16 @@ extern const char linux_proc_banner[]; #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d)) #define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y)) +/** + * upper_32_bits - return bits 32-63 of a number + * @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)) + #define KERN_EMERG "<0>" /* system is unusable */ #define KERN_ALERT "<1>" /* action must be taken immediately */ #define KERN_CRIT "<2>" /* critical conditions */ -- cgit v1.2.3-18-g5258