Hi Wolfram,
Thanks for your feedback.
On 2018-07-18 11:44:13 +0200, Wolfram Sang wrote:
>
> > > One idea I have is to let the loop iterate only over tap_num and then
> > > use a mask 'BIT(i) | BIT(i+tap_num)' and work with binary operators
> > > then. But maybe there are also macros to test and clear bit patterns?
> >
> > I agree that the loop is clumsy. Unfortunately I can't find any bitmap
> > operations that work with bit patterns. If this where just integers the
> > following would have been a better solution:
> >
> > mask = (1 << host->tap_num) - 1;
> > taps = (host->taps & (host->taps >> host->tap_num)) & mask;
> > host->taps = (taps << host->tap_num) | taps;
>
> My above sketch doesn't work?
>
> for (i = 0; i < host->tap_num; i++) {
> mask = BIT(i) | BIT(i + host->tap_num);
> if (host->taps & mask != mask)
> host->taps &= ~mask;
> }
>
> Written from top of my head, maybe I overlooked something.
>
Unfortunately not as host->taps is declared as a bitmap
DECLARE_BITMAP(taps, BITS_PER_BYTE * sizeof(long));
So trying your sketch results in errors.
drivers/mmc/host/renesas_sdhi_core.c:394:32: error: invalid operands to binary & (have 'long unsigned int *' and 'int')
if (host->taps & mask != mask)
~~~~ ^ ~~~~~~~~~~~~
drivers/mmc/host/renesas_sdhi_core.c:395:36: error: assignment to expression with array type
host->taps &= ~mask;
I'm sure one could dereference the host->taps variable and do the bit
operations but that feels like a bad idea. The other option is to use
bitmap_{from,to}_arr32() to access the bitmap as 32 bit integers but
that too feels odd and more complex then using the bitmap helper
functions.
I will await your feedback before on this before I post the next version
of this series.
--
Regards,
Niklas Söderlund
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