Input: ads7846 - pluggable filtering logic

Some LCDs like the LS041Y3 require a customized filtering
logic for reliable readings, so make the filtering function
replacable through platform specific hooks.

Signed-off-by: Imre Deak <imre.deak@solidboot.com>
Signed-off-by: Juha Yrjola <juha.yrjola@solidboot.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

diff --git a/drivers/input/touchscreen/ads7846.c b/drivers/input/touchscreen/ads7846.c
index c6164b6..03e527c 100644 (file)
--- a/drivers/input/touchscreen/ads7846.c
+++ b/drivers/input/touchscreen/ads7846.c
@@ -63,11 +63,11 @@ struct ts_event {
        /* For portability, we can't read 12 bit values using SPI (which
         * would make the controller deliver them as native byteorder u16
         * with msbs zeroed).  Instead, we read them as two 8-bit values,
-        * which need byteswapping then range adjustment.
+        * *** WHICH NEED BYTESWAPPING *** and range adjustment.
         */
-       __be16 x;
-       __be16 y;
-       __be16 z1, z2;
+       u16     x;
+       u16     y;
+       u16     z1, z2;
        int    ignore;
 };
 
@@ -106,6 +106,9 @@ struct ads7846 {
        unsigned                irq_disabled:1; /* P: lock */
        unsigned                disabled:1;
 
+       int                     (*filter)(void *data, int data_idx, int *val);
+       void                    *filter_data;
+       void                    (*filter_cleanup)(void *data);
        int                     (*get_pendown_state)(void);
 };
 
@@ -379,13 +382,13 @@ static void ads7846_rx(void *ads)
        u16                     x, y, z1, z2;
        unsigned long           flags;
 
-       /* adjust:  on-wire is a must-ignore bit, a BE12 value, then padding;
-        * built from two 8 bit values written msb-first.
+       /* ads7846_rx_val() did in-place conversion (including byteswap) from
+        * on-the-wire format as part of debouncing to get stable readings.
         */
-       x = (be16_to_cpu(ts->tc.x) >> 3) & 0x0fff;
-       y = (be16_to_cpu(ts->tc.y) >> 3) & 0x0fff;
-       z1 = (be16_to_cpu(ts->tc.z1) >> 3) & 0x0fff;
-       z2 = (be16_to_cpu(ts->tc.z2) >> 3) & 0x0fff;
+       x = ts->tc.x;
+       y = ts->tc.y;
+       z1 = ts->tc.z1;
+       z2 = ts->tc.z2;
 
        /* range filtering */
        if (x == MAX_12BIT)
@@ -453,50 +456,85 @@ static void ads7846_rx(void *ads)
        spin_unlock_irqrestore(&ts->lock, flags);
 }
 
-static void ads7846_debounce(void *ads)
+static int ads7846_debounce(void *ads, int data_idx, int *val)
 {
        struct ads7846          *ts = ads;
-       struct spi_message      *m;
-       struct spi_transfer     *t;
-       int                     val;
-       int                     status;
 
-       m = &ts->msg[ts->msg_idx];
-       t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);
-       val = (be16_to_cpu(*(__be16 *)t->rx_buf) >> 3) & 0x0fff;
-       if (!ts->read_cnt || (abs(ts->last_read - val) > ts->debounce_tol)) {
+       if (!ts->read_cnt || (abs(ts->last_read - *val) > ts->debounce_tol)) {
+               /* Start over collecting consistent readings. */
+               ts->read_rep = 0;
                /* Repeat it, if this was the first read or the read
                 * wasn't consistent enough. */
                if (ts->read_cnt < ts->debounce_max) {
-                       ts->last_read = val;
+                       ts->last_read = *val;
                        ts->read_cnt++;
+                       return ADS7846_FILTER_REPEAT;
                } else {
                        /* Maximum number of debouncing reached and still
                         * not enough number of consistent readings. Abort
                         * the whole sample, repeat it in the next sampling
                         * period.
                         */
-                       ts->tc.ignore = 1;
                        ts->read_cnt = 0;
-                       /* Last message will contain ads7846_rx() as the
-                        * completion function.
-                        */
-                       m = ts->last_msg;
+                       return ADS7846_FILTER_IGNORE;
                }
-               /* Start over collecting consistent readings. */
-               ts->read_rep = 0;
        } else {
                if (++ts->read_rep > ts->debounce_rep) {
                        /* Got a good reading for this coordinate,
                         * go for the next one. */
-                       ts->tc.ignore = 0;
-                       ts->msg_idx++;
                        ts->read_cnt = 0;
                        ts->read_rep = 0;
-                       m++;
-               } else
+                       return ADS7846_FILTER_OK;
+               } else {
                        /* Read more values that are consistent. */
                        ts->read_cnt++;
+                       return ADS7846_FILTER_REPEAT;
+               }
+       }
+}
+
+static int ads7846_no_filter(void *ads, int data_idx, int *val)
+{
+       return ADS7846_FILTER_OK;
+}
+
+static void ads7846_rx_val(void *ads)
+{
+       struct ads7846 *ts = ads;
+       struct spi_message *m;
+       struct spi_transfer *t;
+       u16 *rx_val;
+       int val;
+       int action;
+       int status;
+
+       m = &ts->msg[ts->msg_idx];
+       t = list_entry(m->transfers.prev, struct spi_transfer, transfer_list);
+       rx_val = t->rx_buf;
+
+       /* adjust:  on-wire is a must-ignore bit, a BE12 value, then padding;
+        * built from two 8 bit values written msb-first.
+        */
+       val = be16_to_cpu(*rx_val) >> 3;
+
+       action = ts->filter(ts->filter_data, ts->msg_idx, &val);
+       switch (action) {
+       case ADS7846_FILTER_REPEAT:
+               break;
+       case ADS7846_FILTER_IGNORE:
+               ts->tc.ignore = 1;
+               /* Last message will contain ads7846_rx() as the
+                * completion function.
+                */
+               m = ts->last_msg;
+               break;
+       case ADS7846_FILTER_OK:
+               *rx_val = val;
+               ts->tc.ignore = 0;
+               m = &ts->msg[++ts->msg_idx];
+               break;
+       default:
+               BUG();
        }
        status = spi_async(ts->spi, m);
        if (status)
@@ -689,14 +727,25 @@ static int __devinit ads7846_probe(struct spi_device *spi)
        ts->vref_delay_usecs = pdata->vref_delay_usecs ? : 100;
        ts->x_plate_ohms = pdata->x_plate_ohms ? : 400;
        ts->pressure_max = pdata->pressure_max ? : ~0;
-       if (pdata->debounce_max) {
+
+       if (pdata->filter != NULL) {
+               if (pdata->filter_init != NULL) {
+                       err = pdata->filter_init(pdata, &ts->filter_data);
+                       if (err < 0)
+                               goto err_free_mem;
+               }
+               ts->filter = pdata->filter;
+               ts->filter_cleanup = pdata->filter_cleanup;
+       } else if (pdata->debounce_max) {
                ts->debounce_max = pdata->debounce_max;
+               if (ts->debounce_max < 2)
+                       ts->debounce_max = 2;
                ts->debounce_tol = pdata->debounce_tol;
                ts->debounce_rep = pdata->debounce_rep;
-               if (ts->debounce_rep > ts->debounce_max + 1)
-                       ts->debounce_rep = ts->debounce_max - 1;
+               ts->filter = ads7846_debounce;
+               ts->filter_data = ts;
        } else
-               ts->debounce_tol = ~0;
+               ts->filter = ads7846_no_filter;
        ts->get_pendown_state = pdata->get_pendown_state;
 
        snprintf(ts->phys, sizeof(ts->phys), "%s/input0", spi->dev.bus_id);
@@ -737,7 +786,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
        x->len = 2;
        spi_message_add_tail(x, m);
 
-       m->complete = ads7846_debounce;
+       m->complete = ads7846_rx_val;
        m->context = ts;
 
        m++;
@@ -755,7 +804,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
        x->len = 2;
        spi_message_add_tail(x, m);
 
-       m->complete = ads7846_debounce;
+       m->complete = ads7846_rx_val;
        m->context = ts;
 
        /* turn y+ off, x- on; we'll use formula #2 */
@@ -774,7 +823,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
                x->len = 2;
                spi_message_add_tail(x, m);
 
-               m->complete = ads7846_debounce;
+               m->complete = ads7846_rx_val;
                m->context = ts;
 
                m++;
@@ -791,7 +840,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
                x->len = 2;
                spi_message_add_tail(x, m);
 
-               m->complete = ads7846_debounce;
+               m->complete = ads7846_rx_val;
                m->context = ts;
        }
 
@@ -820,7 +869,7 @@ static int __devinit ads7846_probe(struct spi_device *spi)
                        spi->dev.driver->name, ts)) {
                dev_dbg(&spi->dev, "irq %d busy?\n", spi->irq);
                err = -EBUSY;
-               goto err_free_mem;
+               goto err_cleanup_filter;
        }
 
        dev_info(&spi->dev, "touchscreen, irq %d\n", spi->irq);
@@ -856,6 +905,9 @@ static int __devinit ads7846_probe(struct spi_device *spi)
        sysfs_remove_group(&spi->dev.kobj, ts->attr_group);
  err_free_irq:
        free_irq(spi->irq, ts);
+ err_cleanup_filter:
+       if (ts->filter_cleanup)
+               ts->filter_cleanup(ts->filter_data);
  err_free_mem:
        input_free_device(input_dev);
        kfree(ts);
@@ -876,6 +928,9 @@ static int __devexit ads7846_remove(struct spi_device *spi)
        /* suspend left the IRQ disabled */
        enable_irq(ts->spi->irq);
 
+       if (ts->filter_cleanup)
+               ts->filter_cleanup(ts->filter_data);
+
        kfree(ts);
 
        dev_dbg(&spi->dev, "unregistered touchscreen\n");

diff --git a/include/linux/spi/ads7846.h b/include/linux/spi/ads7846.h
index adb3daf..1663f94 100644 (file)
--- a/include/linux/spi/ads7846.h
+++ b/include/linux/spi/ads7846.h
@@ -5,6 +5,12 @@
  *
  * It's OK if the min/max values are zero.
  */
+enum ads7846_filter {
+       ADS7846_FILTER_OK,
+       ADS7846_FILTER_REPEAT,
+       ADS7846_FILTER_IGNORE,
+};
+
 struct ads7846_platform_data {
        u16     model;                  /* 7843, 7845, 7846. */
        u16     vref_delay_usecs;       /* 0 for external vref; etc */
@@ -21,5 +27,9 @@ struct ads7846_platform_data {
        u16     debounce_rep;           /* additional consecutive good readings
                                         * required after the first two */
        int     (*get_pendown_state)(void);
+       int     (*filter_init)  (struct ads7846_platform_data *pdata,
+                                void **filter_data);
+       int     (*filter)       (void *filter_data, int data_idx, int *val);
+       void    (*filter_cleanup)(void *filter_data);
 };