Re: [PATCH 1/1] unify DMA_..BIT_MASK definitions: v3.1

Borislav Petkov
2007-10-06T08:47:58Z

On Fri, Oct 05, 2007 at 02:00:50PM -0700, Andrew Morton wrote:
> On Fri, 05 Oct 2007 13:43:54 -0700
> Jeremy Fitzhardinge <jeremy@goop.org> wrote:
>
> > Andrew Morton wrote:
> > > From: Andrew Morton <akpm@linux-foundation.org>
> > >
> > > Now that we have DMA_BIT_MASK(), these macros are pointless.
> > >
> >
> > Except, unfortunately, DMA_64BIT_MASK. I guess we could special case
> > it, assuming this works in all the contexts the macro is used in (ie,
> > compile-time constant?):
> >
> > #define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
> >
>
> doh. Thanks.
>
> --- a/include/linux/dma-mapping.h~stop-using-dma_xxbit_mask-fix
> +++ a/include/linux/dma-mapping.h
> @@ -13,7 +13,7 @@ enum dma_data_direction {
> DMA_NONE = 3,
> };
>
> -#define DMA_BIT_MASK(n) ((1ULL<<(n))-1)
> +#define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
>
> /*
> * NOTE: do not use the below macros in new code and do not add new definitions
> @@ -21,7 +21,7 @@ enum dma_data_direction {
> *
> * Instead, just open-code DMA_BIT_MASK(n) within your driver
> */
> -#define DMA_64BIT_MASK (~0ULL)
> +#define DMA_64BIT_MASK DMA_BIT_MASK(64)
> #define DMA_48BIT_MASK DMA_BIT_MASK(48)
> #define DMA_47BIT_MASK DMA_BIT_MASK(47)
> #define DMA_40BIT_MASK DMA_BIT_MASK(40)
>

Hi and sorry for the late reply. IMHO, this solution is the most concise and still
clear enough a macro to understand what it does after a quick scan (unlike
uglies like IO_COND() in lib/iomap.c¹, :)) And, as a next step, we probably
should do

perl -pi -e 's/DMA_(..)BIT_MASK/DMA_BIT_MASK($1)/g' *

after removing the #define DMA_..BIT_MASK defines in /include/linux/dma-mapping.h
and the other two headers in the original patch after the x86 merge.
Current git (9f34073b4e54ad58541e0e2b4a87f4f6c1460e21) contains about 394
instances of usage of those macros, including the #definitions.

¹ this is not a flame!
--
Regards/Gruß,
Boris.