Dmitry Torokhov <[EMAIL PROTECTED]> writes:
> On Wed, 02 Feb 2005 13:07:21 -0800 (PST), Peter Osterlund
> <[EMAIL PROTECTED]> wrote:
> > + if (mousedev->pkt_count >= 2) {
> > + tmp = ((fx(0) - fx(2)) * (250 *
> > FRACTION_DENOM)) / size;
> > + tmp += mousedev->frac_dx;
> > + mousedev->packet.dx = tmp /
> > FRACTION_DENOM;
> > + mousedev->frac_dx = tmp -
> > mousedev->packet.dx * FRACTION_DENOM;
> > + }
>
> What about setting scale to 256 and fractions to 128 - that should
> save some cycles? Or it will be too much?
It at least saves 32 bytes of object code. The mouse pointer speed
increase will only be 256/250, or 2.4%, so shouldn't be a problem.
Setting FRACTION_DENOM to a larger value is actually a good thing as
long as it doesn't cause arithmetic overflow.
Here is an updated patch:
Signed-off-by: Peter Osterlund <[EMAIL PROTECTED]>
---
linux-petero/drivers/input/mousedev.c | 26 +++++++++++++++++---------
1 files changed, 17 insertions(+), 9 deletions(-)
diff -puN drivers/input/mousedev.c~mousedev-roundoff drivers/input/mousedev.c
--- linux/drivers/input/mousedev.c~mousedev-roundoff 2005-02-02
20:54:23.000000000 +0100
+++ linux-petero/drivers/input/mousedev.c 2005-02-02 22:20:15.000000000
+0100
@@ -71,6 +71,7 @@ struct mousedev {
struct mousedev_hw_data packet;
unsigned int pkt_count;
int old_x[4], old_y[4];
+ int frac_dx, frac_dy;
unsigned long touch;
};
@@ -117,24 +118,31 @@ static struct mousedev mousedev_mix;
static void mousedev_touchpad_event(struct input_dev *dev, struct mousedev
*mousedev, unsigned int code, int value)
{
- int size;
+ int size, tmp;
+#define FRACTION_DENOM 128
if (mousedev->touch) {
+ size = dev->absmax[ABS_X] - dev->absmin[ABS_X];
+ if (size == 0) size = xres;
switch (code) {
case ABS_X:
- size = dev->absmax[ABS_X] - dev->absmin[ABS_X];
- if (size == 0) size = xres;
fx(0) = value;
- if (mousedev->pkt_count >= 2)
- mousedev->packet.dx = ((fx(0) - fx(1))
/ 2 + (fx(1) - fx(2)) / 2) * xres / (size * 2);
+ if (mousedev->pkt_count >= 2) {
+ tmp = ((fx(0) - fx(2)) * (256 *
FRACTION_DENOM)) / size;
+ tmp += mousedev->frac_dx;
+ mousedev->packet.dx = tmp /
FRACTION_DENOM;
+ mousedev->frac_dx = tmp -
mousedev->packet.dx * FRACTION_DENOM;
+ }
break;
case ABS_Y:
- size = dev->absmax[ABS_Y] - dev->absmin[ABS_Y];
- if (size == 0) size = yres;
fy(0) = value;
- if (mousedev->pkt_count >= 2)
- mousedev->packet.dy = -((fy(0) - fy(1))
/ 2 + (fy(1) - fy(2)) / 2) * yres / (size * 2);
+ if (mousedev->pkt_count >= 2) {
+ tmp = -((fy(0) - fy(2)) * (256 *
FRACTION_DENOM)) / size;
+ tmp += mousedev->frac_dy;
+ mousedev->packet.dy = tmp /
FRACTION_DENOM;
+ mousedev->frac_dy = tmp -
mousedev->packet.dy * FRACTION_DENOM;
+ }
break;
}
}
_
--
Peter Osterlund - [EMAIL PROTECTED]
http://web.telia.com/~u89404340
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