Input: cros_ec_keyb - optimize ghosting algorithm
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 <tbroch@chromium.org>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Luigi Semenzato <semenzato@chromium.org>
Tested-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c
index 791781a..72d3499 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 @@
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 @@
};
-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 @@
*
* 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;
}
+
/*
* Compares the new keyboard state to the old one and produces key
* press/release events accordingly. The keyboard state is 13 bytes (one byte
@@ -222,6 +197,30 @@
free_irq(ec->irq, ckdev);
}
+/*
+ * Walks keycodes flipping bit in buffer COLUMNS deep where bit is ROW. Used by
+ * ghosting logic to ignore NULL or virtual keys.
+ */
+static void cros_ec_keyb_compute_valid_keys(struct cros_ec_keyb *ckdev)
+{
+ int row, col;
+ int row_shift = ckdev->row_shift;
+ unsigned short *keymap = ckdev->idev->keycode;
+ unsigned short code;
+
+ BUG_ON(ckdev->idev->keycodesize != sizeof(*keymap));
+
+ for (col = 0; col < ckdev->cols; col++) {
+ for (row = 0; row < ckdev->rows; row++) {
+ code = keymap[MATRIX_SCAN_CODE(row, col, row_shift)];
+ if (code && (code != KEY_BATTERY))
+ ckdev->valid_keys[col] |= 1 << row;
+ }
+ dev_dbg(ckdev->dev, "valid_keys[%02d] = 0x%02x\n",
+ col, ckdev->valid_keys[col]);
+ }
+}
+
static int cros_ec_keyb_probe(struct platform_device *pdev)
{
struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
@@ -242,6 +241,11 @@
&ckdev->cols);
if (err)
return err;
+
+ ckdev->valid_keys = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
+ if (!ckdev->valid_keys)
+ return -ENOMEM;
+
ckdev->old_kb_state = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
if (!ckdev->old_kb_state)
return -ENOMEM;
@@ -285,6 +289,8 @@
input_set_capability(idev, EV_MSC, MSC_SCAN);
input_set_drvdata(idev, ckdev);
ckdev->idev = idev;
+ cros_ec_keyb_compute_valid_keys(ckdev);
+
err = input_register_device(ckdev->idev);
if (err) {
dev_err(dev, "cannot register input device\n");