Re: [Xen-devel] [for-4.7 1/2] xen/bitops: Introduce macros to generate mask

["Jan Beulich" <jbeulich@xxxxxxxx>]

>>> Julien Grall <julien.grall@xxxxxxx> 04/13/16 6:01 PM >>>
>--- a/xen/include/xen/bitops.h
>+++ b/xen/include/xen/bitops.h
>@@ -3,6 +3,17 @@
 >#include <asm/types.h>
 >
 >/*
>+ * Create a contiguous bitmask starting at bit position @l and ending at
>+ * position @h. For example
>+ * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
>+ */
>+#define GENMASK(h, l) \
>+    (((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
>+
>+#define GENMASK_ULL(h, l) \
>+    (((~0ULL) << (l)) & (~0ULL >> (BITS_PER_LONG_LONG - 1 - (h))))

Irrespective of Linux perhaps considering them useful, I'm not sure they
are (and ISTR these macros having got proposed before). Plus - I don't
think we even have BITS_PER_LONG_LONG anywhere.

Jan


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