Messages in this thread | | | Date | Wed, 9 Dec 2009 11:57:00 +0200 | From | Dan Carpenter <> | Subject | Re: [PATCH] staging: s5k3e2fx.c: reduce complexity by factoring |
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On Sat, Dec 05, 2009 at 06:03:20PM -0800, Justin Madru wrote: > I was style fixing some code when I ran into this code. > It seems like the code could be reduced, by factoring the expression. > But this results in a very simple expression. > > Am I assuming something wrong? Or is this a bug in the original code? > This doesn't look right because the assignment of s_move[i] has no mention > of the loop counter. > > Justin > > ------ > > the code was looping, seting s_move[i] to the following calculations > > if (actual_step >= 0) > s_move[i] = ((((i + 1) * gain + 0x200) - (i * gain + 0x200)) / 0x400); > else > s_move[i] = ((((i + 1) * gain - 0x200) - (i * gain - 0x200)) / 0x400); > > but, by factoring the expression, it can be shown that they both reduce > to a very simple expression: > > s_move[i] = gain / 0x400; >
Heh.
Looks like an improvement to me.
If gain were 16 bits instead of 32 I would think the "* 0x400 / 0x400" was designed to mask out the highest 10 bits.
Acked-by: Dan Carpenter <error27@gmail.com>
regards, dan carpenter
> Signed-off-by: Justin Madru <jdm64@gawab.com> > --- > drivers/staging/dream/camera/s5k3e2fx.c | 10 +++------- > 1 files changed, 3 insertions(+), 7 deletions(-) > > diff --git a/drivers/staging/dream/camera/s5k3e2fx.c b/drivers/staging/dream/camera/s5k3e2fx.c > index f0e49be..d205a2d 100644 > --- a/drivers/staging/dream/camera/s5k3e2fx.c > +++ b/drivers/staging/dream/camera/s5k3e2fx.c > @@ -1092,14 +1092,10 @@ static int32_t s5k3e2fx_move_focus(int direction, int32_t num_steps) > > actual_step = step_direction * (int16_t)num_steps; > pos_offset = init_code + s5k3e2fx_ctrl->curr_lens_pos; > - gain = actual_step * 0x400 / 5; > + gain = actual_step / 5; > > - for (i = 0; i <= 4; i++) { > - if (actual_step >= 0) > - s_move[i] = ((((i+1)*gain+0x200) - (i*gain+0x200))/0x400); > - else > - s_move[i] = ((((i+1)*gain-0x200) - (i*gain-0x200))/0x400); > - } > + for (i = 0; i <= 4; i++) > + s_move[i] = gain; > > /* Ring Damping Code */ > for (i = 0; i <= 4; i++) { > -- > 1.6.5.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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