Input: tegra-kbc - add ghost key filter
Add ghost key filtering support for the Nvidia Tegra matrix keyboard.
Signed-off-by: Rakesh Iyer <riyer@nvidia.com>
Reviewed-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/keyboard/tegra-kbc.c b/drivers/input/keyboard/tegra-kbc.c
index 99ce903..5fb4b97 100644
--- a/drivers/input/keyboard/tegra-kbc.c
+++ b/drivers/input/keyboard/tegra-kbc.c
@@ -72,6 +72,7 @@
unsigned int repoll_dly;
unsigned long cp_dly_jiffies;
bool use_fn_map;
+ bool use_ghost_filter;
const struct tegra_kbc_platform_data *pdata;
unsigned short keycode[KBC_MAX_KEY * 2];
unsigned short current_keys[KBC_MAX_KPENT];
@@ -260,6 +261,8 @@
unsigned int num_down = 0;
unsigned long flags;
bool fn_keypress = false;
+ bool key_in_same_row = false;
+ bool key_in_same_col = false;
spin_lock_irqsave(&kbc->lock, flags);
for (i = 0; i < KBC_MAX_KPENT; i++) {
@@ -285,6 +288,34 @@
}
/*
+ * Matrix keyboard designs are prone to keyboard ghosting.
+ * Ghosting occurs if there are 3 keys such that -
+ * any 2 of the 3 keys share a row, and any 2 of them share a column.
+ * If so ignore the key presses for this iteration.
+ */
+ if ((kbc->use_ghost_filter) && (num_down >= 3)) {
+ for (i = 0; i < num_down; i++) {
+ unsigned int j;
+ u8 curr_col = scancodes[i] & 0x07;
+ u8 curr_row = scancodes[i] >> KBC_ROW_SHIFT;
+
+ /*
+ * Find 2 keys such that one key is in the same row
+ * and the other is in the same column as the i-th key.
+ */
+ for (j = i + 1; j < num_down; j++) {
+ u8 col = scancodes[j] & 0x07;
+ u8 row = scancodes[j] >> KBC_ROW_SHIFT;
+
+ if (col == curr_col)
+ key_in_same_col = true;
+ if (row == curr_row)
+ key_in_same_row = true;
+ }
+ }
+ }
+
+ /*
* If the platform uses Fn keymaps, translate keys on a Fn keypress.
* Function keycodes are KBC_MAX_KEY apart from the plain keycodes.
*/
@@ -297,6 +328,10 @@
spin_unlock_irqrestore(&kbc->lock, flags);
+ /* Ignore the key presses for this iteration? */
+ if (key_in_same_col && key_in_same_row)
+ return;
+
tegra_kbc_report_released_keys(kbc->idev,
kbc->current_keys, kbc->num_pressed_keys,
keycodes, num_down);
@@ -652,6 +687,7 @@
input_dev->keycodemax *= 2;
kbc->use_fn_map = pdata->use_fn_map;
+ kbc->use_ghost_filter = pdata->use_ghost_filter;
keymap_data = pdata->keymap_data ?: &tegra_kbc_default_keymap_data;
matrix_keypad_build_keymap(keymap_data, KBC_ROW_SHIFT,
input_dev->keycode, input_dev->keybit);