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SubjectRe: [PATCH] Staging: d53155_drv.c: cleanup fbuffer usage
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On Thu, 2010-06-24 at 09:31 -0700, H Hartley Sweeten wrote:
> The global symbol dt3155_fbuffer[], declared in dt3155_isr.c, is really
> just a pointer to dt3155_status[].fbuffer. To improve readability, make
> some of the really long lines shorter, and make the buffer access more
> consistent, use &dt3155_status[].fbuffer to access the buffer structure.

I think this would be more consistent/intelligible
if the temporary wasn't
struct dt3155_fbuffer *fb = &dt3155_status[minor].fbuffer;
but was
struct dt3155_status *dts = &dt3155_status[minor];

> @@ -146,11 +148,11 @@ static void quick_stop (int minor)
> dt3155_status[minor].state &= ~(DT3155_STATE_STOP|0xff);
> /* mark the system stopped: */
> dt3155_status[minor].state |= DT3155_STATE_IDLE;
> - dt3155_fbuffer[minor]->stop_acquire = 0;
> - dt3155_fbuffer[minor]->even_stopped = 0;
> + fb->stop_acquire = 0;
> + fb->even_stopped = 0;
> #else
> dt3155_status[minor].state |= DT3155_STATE_STOP;
> - dt3155_status[minor].fbuffer.stop_acquire = 1;
> + fb->stop_acquire = 1;
> #endif

becomes

dts->state &= ~(DT3155_STATE_STOP|0xff);
/* mark the system stopped: */
dts->state |= DT3155_STATE_IDLE;
dts->fbuffer.stop_acquire = 0;
dts->fbuffer.even_stopped = 0;
#else
dts->fbuffer.stop_acquire = 1;
#endif
Another option might be to use dereferencing inlines.

static inline struct dt3155_status *dts(int index)
{
return &dt3155_status[index];
}
static inline struct dt3155_fbuffer *fb(int index)
{
return &(dts(index)->fbuffer);
}
I think this isn't as good as the temporary because the
compiler sometimes doesn't reuse the intermediate addresses
and the inlines have file rather than function scope.

It becomes something like:

dts(minor)->state &= ~(DT3155_STATE_STOP|0xff);
/* mark the system stopped: */
dts(minor)->state |= DT3155_STATE_IDLE;
fb(minor)->stop_acquire = 0;
fb(minor)->even_stopped = 0;
#else
fb(minor)->stop_acquire = 1;
#endif
I think this isn't as good as the temporary because the
compiler sometimes doesn't reuse the intermediate addresses
and the macros have file rather than function scope.




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