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Input: ads7846 - re-check pendown status before reporting events

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Pendown status from the PENIRQ pin is currently read only at the beginning
of a sample set. If the pen is lifted just after sampling has began then
sampled values become wrong.

This patch adds an optional platform penirq_recheck_delay attribute.  If
non-zero, samples are only reported to the input subsystem if PENIRQ is
still active that long after the samples taken.

Signed-off-by: Semih Hazar <semih.hazar@indefia.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
This commit is contained in:
Semih Hazar 2007-07-18 00:36:04 -04:00 committed by Dmitry Torokhov
parent e4f4886199
commit 1d25891f32
2 changed files with 21 additions and 0 deletions
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15
drivers/input/touchscreen/ads7846.c
View file

@ -107,6 +107,8 @@ struct ads7846 {
u16 debounce_tol;
u16 debounce_rep;
u16 penirq_recheck_delay_usecs;
spinlock_t lock;
struct hrtimer timer;
unsigned pendown:1; /* P: lock */
@ -553,6 +555,15 @@ static void ads7846_rx(void *ads)
return;
}
/* Maybe check the pendown state before reporting. This discards
* false readings when the pen is lifted.
*/
if (ts->penirq_recheck_delay_usecs) {
udelay(ts->penirq_recheck_delay_usecs);
if (!ts->get_pendown_state())
Rt = 0;
}
/* NOTE: We can't rely on the pressure to determine the pen down
* state, even this controller has a pressure sensor. The pressure
* value can fluctuate for quite a while after lifting the pen and
@ -896,6 +907,10 @@ static int __devinit ads7846_probe(struct spi_device *spi)
ts->filter = ads7846_no_filter;
ts->get_pendown_state = pdata->get_pendown_state;
if (pdata->penirq_recheck_delay_usecs)
ts->penirq_recheck_delay_usecs =
pdata->penirq_recheck_delay_usecs;
snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
input_dev->name = "ADS784x Touchscreen";

6
include/linux/spi/ads7846.h
View file

@ -24,6 +24,12 @@ struct ads7846_platform_data {
*/
u16 settle_delay_usecs;
/* If set to non-zero, after samples are taken this delay is applied
* and penirq is rechecked, to help avoid false events. This value
* is affected by the material used to build the touch layer.
*/
u16 penirq_recheck_delay_usecs;
u16 x_plate_ohms;
u16 y_plate_ohms;