On Wed, Oct 16, 2013 at 07:59:09PM -0700, Joe Perches wrote: > Date: Wed, 16 Oct 2013 19:59:09 -0700 > From: Joe Perches <joe@xxxxxxxxxxx> > To: "Chen, Gong" <gong.chen@xxxxxxxxxxxxxxx> > Cc: tony.luck@xxxxxxxxx, bp@xxxxxxxxx, naveen.n.rao@xxxxxxxxxxxxxxxxxx, > m.chehab@xxxxxxxxxxx, arozansk@xxxxxxxxxx, linux-acpi@xxxxxxxxxxxxxxx, > linux-kernel@xxxxxxxxxxxxxxx, Thomas Winischhofer > <thomas@xxxxxxxxxxxxxxxx>, Jean-Christophe Plagniol-Villard > <plagnioj@xxxxxxxxxxxx>, Tomi Valkeinen <tomi.valkeinen@xxxxxx> > Subject: Re: [PATCH v2 3/9] bitops: Introduce a more generic BITMASK macro > X-Mailer: Evolution 3.6.4-0ubuntu1 > > On Wed, 2013-10-16 at 10:56 -0400, Chen, Gong wrote: > > GENMASK is used to create a contiguous bitmask([hi:lo]). It is > > implemented twice in current kernel. One is in EDAC driver, the other > > is in SiS/XGI FB driver. Move it to a more generic place for other > > usage. > [] > > diff --git a/include/linux/bitops.h b/include/linux/bitops.h > [] > > @@ -10,6 +10,14 @@ > > #define BITS_TO_LONGS(nr) DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long)) > > #endif > > > > +/* > > + * 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. > > ull > > > + */ > > +#define GENMASK(h, l) (((U32_C(1) << ((h) - (l) + 1)) - 1) << (l)) > > +#define GENMASK_ULL(h, l) (((U64_C(1) << ((h) - (l) + 1)) - 1) << (l)) > > > Maybe add a > > BUILD_BUG_ON(__builtin_constant_p(l) && __builtin_constant_p(h) && \ > (h) < (l)) > No, if so, users can't use variables for this macro.
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