[alsa-devel] [PATCH] alsa: add annotations to bitwise type snd_pcm_hw_param_t

Al Viro viro at ZenIV.linux.org.uk
Sun Jun 22 09:50:40 CEST 2008

On Wed, Jun 18, 2008 at 01:45:13PM -0700, Harvey Harrison wrote:
> Fully half of all alsa sparse warnings are from snd_pcm_hw_param_t degrading
> to integer type, this goes a long way towards eliminating them.

FWIW, *all* this stuff is not bitwise at all.  For crying out loud, half
of these types are routinely used as array indices and loop variables...

If anything, we want a different set of allowed operations - subtraction
between elements of type (yielding integer), addition/subtraction of
integer types not bigger than ours (yielding our type), comparisons,
assignments (=, +=, -=, passing to function as argument, return from
function, initializers) and second/third arguments in ?:.  With 0 *not*
being allowed as a constant of such type.

It's not bitwise; we may use the same infrastructure in sparse, but it
should be a separate class of types (__attribute__((affine))).

dma_addr_t is another candidate for the same treatment, but there we'll
need helpers for conversions to hw-acceptable form (dma_to_le32(), etc.)
and gradual conversion of drivers.

ALSA ones and pm mess are absolutely straightforward cases, though.

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