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authorAndrew Morton <akpm@linux-foundation.org>2007-05-10 03:15:18 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-10 09:26:52 -0700
commit218e180e7ea5334e1f94121940ba82cd1f0f4e58 (patch)
tree5b7aa47a2439c40b8b68a3bfd9e2f72bf07cf385 /include
parent894b8788d7f265eb7c6f75a9a77cedeb48f51586 (diff)
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 <James.Bottomley@SteelEye.com> Cc: "Cameron, Steve" <Steve.Cameron@hp.com> Cc: "Miller, Mike (OS Dev)" <Mike.Miller@hp.com> Cc: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/kernel.h10
1 files changed, 10 insertions, 0 deletions
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 */