Messages in this thread Patch in this message | | | From | Justin Madru <> | Subject | [PATCH] staging: s5k3e2fx.c: simplify complexity by factoring | Date | Tue, 15 Dec 2009 12:52:10 -0800 |
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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, this code redues to the expression s_move[i] = gain >> 10;
The reason for the complexity was to generate a step function with integer division and rounding to land on specific values. But these calculations can be simplified to the following code:
gain = ((actual_step << 10) / 5) >> 10; for (i = 0; i <= 4; i++) s_move[i] = gain; --- 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 edba198..66582af 100644 --- a/drivers/staging/dream/camera/s5k3e2fx.c +++ b/drivers/staging/dream/camera/s5k3e2fx.c @@ -1093,14 +1093,10 @@ 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 << 10) / 5) >> 10; - 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++) { -- 1.6.5.6
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