Messages in this thread | | | Date | Tue, 29 Mar 2011 14:32:46 -0300 | From | Mauro Carvalho Chehab <> | Subject | Re: [PATCH 05/30] amd64_edac: Cleanup chipselect handling |
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Em 29-03-2011 13:02, Borislav Petkov escreveu: > On Tue, Mar 29, 2011 at 11:39:09AM -0400, Mauro Carvalho Chehab wrote: >>>>> + * Create a contiguous bitmask starting at bit position @lo and ending at >>>>> + * position @hi. For example >>>>> + * >>>>> + * GENMASK(21, 39) gives us the 64bit vector 0x000000ffffe00000. >>>>> + */ >>>>> +#define GENMASK(lo, hi) (((1ULL << ((hi) - (lo) + 1)) - 1) << (lo)) >>>>> + >>>> >>>> This is a nice macro that could be useful outside amd64. It is probably a good >>>> idea to move it to include/linux/bitops.h. >>> >>> I'd suggest rather <drivers/edac/edac_core.h> if you want to use it in >>> EDAC. But if we have more users, I don't have a problem with putting >>> it there (or somewhere else generic enough if people have a better >>> suggestion). >> >> Yeah, other edac drivers could benefit of using it, and also could benefit on a >> variant that would do an AND operation and shift it, something like (untested): >> >> /* >> * Create a contiguous bitmask starting at bit position @lo and ending at >> * position @hi. For example >> * >> * APPLY_BITMASK(v, 21, 39) will return the result of: >> * (v & 0x000000ffffe00000) >> 21 >> */ >> #define APPLY_BITMASK(v, lo, hi) (((v) & ((1ULL << ((hi) - (lo) + 1)) - 1) << (lo)) >> (lo)) > > The macro definition doesn't match the comment. In the comment you do a bitwise > AND first and shift the result then. The way you've written it, it does > > ((v & 0x000000000007ffff << 21) >> 21) > > you need to fixup the brackets:
Ah, yes. As I said, it was untested ;) I was in the middle of reviewing lots of edac patches, but I didn't want to loose the idea, so I was quick on my reply ;) > > #define APPLY_BITMASK(v, lo, hi) (((v) & (((1ULL << ((hi) - (lo) + 1)) - 1) << (lo))) >> (lo)) > > Also, this doesn't only apply it but shifts too, so it should be > > #define APPLY_BITMASK_AND_SHIFT(...)
Yeah, that name sounds better ;) > > But this macro gets too special to put it in shared code.
Ok.
> >> Almost all edac drivers do something like the above, for example, to get DIMM rows/cols/banks, etc. >> >> Probably, the most complex part is to find a nice name for it ;) >> >> Yet, I think non-edac drivers could also benefit of such macro, and, as this is not >> edac-specific, I think it would be better to add it at bitops.h. > > No, this should go into generic code only if it has users - "it might > benefit" is not strong-enough an argument for polluting generic code. > I'd leave it in edac_core.h and push it somewhere more generic only when > I need it in other subsystems.
Works for me.
Thanks! Mauro
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