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Input: cros_ec_keyb - optimize ghosting algorithm

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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>
This commit is contained in:
Todd Broch 2014-09-03 16:56:12 -07:00 committed by Dmitry Torokhov
parent 516d5f8b04
commit 017f14e88b
1 changed files with 49 additions and 43 deletions
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92
drivers/input/keyboard/cros_ec_keyb.c
View file

@ -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;
}
/*
* 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 @@ static void cros_ec_keyb_close(struct input_dev *dev)
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 @@ static int cros_ec_keyb_probe(struct platform_device *pdev)
&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 @@ static int cros_ec_keyb_probe(struct platform_device *pdev)
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");