Messages in this thread | | | Date | Mon, 14 Dec 2009 16:38:40 -0800 | From | Justin Madru <> | Subject | Re: [PATCH] staging: s5k3e2fx.c: reduce complexity by factoring |
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On 12/09/2009 01:57 AM, Dan Carpenter wrote: > 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/ >>
I've yet to see a reply from GregH. Has this patch been misplaced or dropped? Or is the patch no longer valid/correct?
Justin Madru
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