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Input: appletouch - fix integer overflow issue

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When reading data from Geyser 2 touchpads used on post Oct 2005 Apple
PowerBooks the driver was casting X and Y coordinates values to
'signed char'. Testing on one of such PowerBooks I have noticed that
touchpad always generates positive values, but some of them are greater
that 127, and thus, when cast to 'signed char' being interpreted as
a negative.

Such bigger values have been observed infrequently, closer to the
edges of a touchpad, so the problem was not very visible.
Nevertheless, the patch would potentially improve touchpad
driver accuracy.

Signed-off-by: Vadim Zaliva <lord@crocodile.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
This commit is contained in:
Vadim Zaliva 2010-03-10 23:41:00 -08:00 committed by Dmitry Torokhov
parent 4eb6f91b95
commit 04b4b88cca
1 changed files with 3 additions and 3 deletions
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6
drivers/input/mouse/appletouch.c
View file

@ -205,8 +205,8 @@ struct atp {
bool overflow_warned;
int x_old; /* last reported x/y, */
int y_old; /* used for smoothing */
signed char xy_cur[ATP_XSENSORS + ATP_YSENSORS];
signed char xy_old[ATP_XSENSORS + ATP_YSENSORS];
u8 xy_cur[ATP_XSENSORS + ATP_YSENSORS];
u8 xy_old[ATP_XSENSORS + ATP_YSENSORS];
int xy_acc[ATP_XSENSORS + ATP_YSENSORS];
int idlecount; /* number of empty packets */
struct work_struct work;
@ -531,7 +531,7 @@ static void atp_complete_geyser_1_2(struct urb *urb)
for (i = 0; i < ATP_XSENSORS + ATP_YSENSORS; i++) {
/* accumulate the change */
signed char change = dev->xy_old[i] - dev->xy_cur[i];
int change = dev->xy_old[i] - dev->xy_cur[i];
dev->xy_acc[i] -= change;
/* prevent down drifting */