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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>
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@ -22,6 +22,7 @@
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*/
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#include <linux/module.h>
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#include <linux/bitops.h>
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#include <linux/i2c.h>
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#include <linux/input.h>
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#include <linux/interrupt.h>
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@ -38,6 +39,7 @@
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* @row_shift: log2 or number of rows, rounded up
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* @keymap_data: Matrix keymap data used to convert to keyscan values
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* @ghost_filter: true to enable the matrix key-ghosting filter
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* @valid_keys: bitmap of existing keys for each matrix column
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* @old_kb_state: bitmap of keys pressed last scan
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* @dev: Device pointer
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* @idev: Input device
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@ -49,6 +51,7 @@ struct cros_ec_keyb {
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int row_shift;
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const struct matrix_keymap_data *keymap_data;
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bool ghost_filter;
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uint8_t *valid_keys;
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uint8_t *old_kb_state;
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struct device *dev;
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@ -57,39 +60,15 @@ struct cros_ec_keyb {
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};
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static bool cros_ec_keyb_row_has_ghosting(struct cros_ec_keyb *ckdev,
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uint8_t *buf, int row)
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{
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int pressed_in_row = 0;
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int row_has_teeth = 0;
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int col, mask;
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mask = 1 << row;
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for (col = 0; col < ckdev->cols; col++) {
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if (buf[col] & mask) {
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pressed_in_row++;
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row_has_teeth |= buf[col] & ~mask;
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if (pressed_in_row > 1 && row_has_teeth) {
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/* ghosting */
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dev_dbg(ckdev->dev,
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"ghost found at: r%d c%d, pressed %d, teeth 0x%x\n",
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row, col, pressed_in_row,
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row_has_teeth);
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return true;
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}
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}
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}
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return false;
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}
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/*
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* Returns true when there is at least one combination of pressed keys that
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* results in ghosting.
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*/
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static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf)
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{
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int row;
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int col1, col2, buf1, buf2;
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struct device *dev = ckdev->dev;
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uint8_t *valid_keys = ckdev->valid_keys;
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/*
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* Ghosting happens if for any pressed key X there are other keys
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@ -103,27 +82,23 @@ static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf)
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*
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* In this case only X, Y, and Z are pressed, but g appears to be
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* pressed too (see Wikipedia).
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*
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* We can detect ghosting in a single pass (*) over the keyboard state
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* by maintaining two arrays. pressed_in_row counts how many pressed
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* keys we have found in a row. row_has_teeth is true if any of the
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* pressed keys for this row has other pressed keys in its column. If
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* at any point of the scan we find that a row has multiple pressed
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* keys, and at least one of them is at the intersection with a column
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* with multiple pressed keys, we're sure there is ghosting.
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* Conversely, if there is ghosting, we will detect such situation for
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* at least one key during the pass.
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*
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* (*) This looks linear in the number of keys, but it's not. We can
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* cheat because the number of rows is small.
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*/
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for (row = 0; row < ckdev->rows; row++)
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if (cros_ec_keyb_row_has_ghosting(ckdev, buf, row))
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return true;
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for (col1 = 0; col1 < ckdev->cols; col1++) {
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buf1 = buf[col1] & valid_keys[col1];
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for (col2 = col1 + 1; col2 < ckdev->cols; col2++) {
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buf2 = buf[col2] & valid_keys[col2];
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if (hweight8(buf1 & buf2) > 1) {
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dev_dbg(dev, "ghost found at: B[%02d]:0x%02x & B[%02d]:0x%02x",
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col1, buf1, col2, buf2);
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return true;
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}
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}
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}
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return false;
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}
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/*
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* Compares the new keyboard state to the old one and produces key
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* press/release events accordingly. The keyboard state is 13 bytes (one byte
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@ -222,6 +197,30 @@ static void cros_ec_keyb_close(struct input_dev *dev)
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free_irq(ec->irq, ckdev);
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}
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/*
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* Walks keycodes flipping bit in buffer COLUMNS deep where bit is ROW. Used by
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* ghosting logic to ignore NULL or virtual keys.
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*/
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static void cros_ec_keyb_compute_valid_keys(struct cros_ec_keyb *ckdev)
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{
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int row, col;
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int row_shift = ckdev->row_shift;
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unsigned short *keymap = ckdev->idev->keycode;
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unsigned short code;
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BUG_ON(ckdev->idev->keycodesize != sizeof(*keymap));
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for (col = 0; col < ckdev->cols; col++) {
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for (row = 0; row < ckdev->rows; row++) {
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code = keymap[MATRIX_SCAN_CODE(row, col, row_shift)];
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if (code && (code != KEY_BATTERY))
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ckdev->valid_keys[col] |= 1 << row;
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}
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dev_dbg(ckdev->dev, "valid_keys[%02d] = 0x%02x\n",
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col, ckdev->valid_keys[col]);
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}
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}
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static int cros_ec_keyb_probe(struct platform_device *pdev)
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{
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struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
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@ -242,6 +241,11 @@ static int cros_ec_keyb_probe(struct platform_device *pdev)
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&ckdev->cols);
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if (err)
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return err;
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ckdev->valid_keys = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
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if (!ckdev->valid_keys)
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return -ENOMEM;
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ckdev->old_kb_state = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
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if (!ckdev->old_kb_state)
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return -ENOMEM;
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@ -285,6 +289,8 @@ static int cros_ec_keyb_probe(struct platform_device *pdev)
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input_set_capability(idev, EV_MSC, MSC_SCAN);
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input_set_drvdata(idev, ckdev);
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ckdev->idev = idev;
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cros_ec_keyb_compute_valid_keys(ckdev);
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err = input_register_device(ckdev->idev);
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if (err) {
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dev_err(dev, "cannot register input device\n");
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