From: Todd Broch tbr...@chromium.org
Previous algorithm was a bit conservative and complicating with
respect to identifying key ghosting. This CL uses the bitops hamming
weight function (hweight8) to count the number of matching rows for
colM colN. If that number is 1 ghosting is present.
Additionally it removes NULL keys and our one virtual keypress
KEY_BATTERY from consideration as these inputs are never physical
keypresses.
Signed-off-by: Todd Broch tbr...@chromium.org
Reviewed-by: Vincent Palatin vpala...@chromium.org
Reviewed-by: Luigi Semenzato semenz...@chromium.org
Tested-by: Andreas Färber afaer...@suse.de
Signed-off-by: Javier Martinez Canillas javier.marti...@collabora.co.uk
---
drivers/input/keyboard/cros_ec_keyb.c | 92 +++
1 file changed, 49 insertions(+), 43 deletions(-)
diff --git a/drivers/input/keyboard/cros_ec_keyb.c
b/drivers/input/keyboard/cros_ec_keyb.c
index f8d4a8b..462bfcb 100644
--- a/drivers/input/keyboard/cros_ec_keyb.c
+++ b/drivers/input/keyboard/cros_ec_keyb.c
@@ -22,6 +22,7 @@
*/
#include linux/module.h
+#include linux/bitops.h
#include linux/i2c.h
#include linux/input.h
#include linux/interrupt.h
@@ -38,6 +39,7 @@
* @row_shift: log2 or number of rows, rounded up
* @keymap_data: Matrix keymap data used to convert to keyscan values
* @ghost_filter: true to enable the matrix key-ghosting filter
+ * @valid_keys: bitmap of existing keys for each matrix column
* @old_kb_state: bitmap of keys pressed last scan
* @dev: Device pointer
* @idev: Input device
@@ -49,6 +51,7 @@ struct cros_ec_keyb {
int row_shift;
const struct matrix_keymap_data *keymap_data;
bool ghost_filter;
+ uint8_t *valid_keys;
uint8_t *old_kb_state;
struct device *dev;
@@ -57,39 +60,15 @@ struct cros_ec_keyb {
};
-static bool cros_ec_keyb_row_has_ghosting(struct cros_ec_keyb *ckdev,
- uint8_t *buf, int row)
-{
- int pressed_in_row = 0;
- int row_has_teeth = 0;
- int col, mask;
-
- mask = 1 row;
- for (col = 0; col ckdev-cols; col++) {
- if (buf[col] mask) {
- pressed_in_row++;
- row_has_teeth |= buf[col] ~mask;
- if (pressed_in_row 1 row_has_teeth) {
- /* ghosting */
- dev_dbg(ckdev-dev,
- ghost found at: r%d c%d, pressed %d,
teeth 0x%x\n,
- row, col, pressed_in_row,
- row_has_teeth);
- return true;
- }
- }
- }
-
- return false;
-}
-
/*
* Returns true when there is at least one combination of pressed keys that
* results in ghosting.
*/
static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf)
{
- int row;
+ int col1, col2, buf1, buf2;
+ struct device *dev = ckdev-dev;
+ uint8_t *valid_keys = ckdev-valid_keys;
/*
* Ghosting happens if for any pressed key X there are other keys
@@ -103,27 +82,23 @@ static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb
*ckdev, uint8_t *buf)
*
* In this case only X, Y, and Z are pressed, but g appears to be
* pressed too (see Wikipedia).
-*
-* We can detect ghosting in a single pass (*) over the keyboard state
-* by maintaining two arrays. pressed_in_row counts how many pressed
-* keys we have found in a row. row_has_teeth is true if any of the
-* pressed keys for this row has other pressed keys in its column. If
-* at any point of the scan we find that a row has multiple pressed
-* keys, and at least one of them is at the intersection with a column
-* with multiple pressed keys, we're sure there is ghosting.
-* Conversely, if there is ghosting, we will detect such situation for
-* at least one key during the pass.
-*
-* (*) This looks linear in the number of keys, but it's not. We can
-* cheat because the number of rows is small.
*/
- for (row = 0; row ckdev-rows; row++)
- if (cros_ec_keyb_row_has_ghosting(ckdev, buf, row))
- return true;
+ for (col1 = 0; col1 ckdev-cols; col1++) {
+ buf1 = buf[col1] valid_keys[col1];
+ for (col2 = col1 + 1; col2 ckdev-cols; col2++) {
+ buf2 = buf[col2] valid_keys[col2];
+ if (hweight8(buf1 buf2) 1) {
+ dev_dbg(dev, ghost found at: B[%02d]:0x%02x
B[%02d]:0x%02x,
+ col1, buf1, col2, buf2);
+ return true;
+ }
+ }
+ }
return false;
}
+
/*
