2 * ChromeOS EC keyboard driver
4 * Copyright (C) 2012 Google, Inc
6 * This software is licensed under the terms of the GNU General Public
7 * License version 2, as published by the Free Software Foundation, and
8 * may be copied, distributed, and modified under those terms.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
15 * This driver uses the Chrome OS EC byte-level message-based protocol for
16 * communicating the keyboard state (which keys are pressed) from a keyboard EC
17 * to the AP over some bus (such as i2c, lpc, spi). The EC does debouncing,
18 * but everything else (including deghosting) is done here. The main
19 * motivation for this is to keep the EC firmware as simple as possible, since
20 * it cannot be easily upgraded and EC flash/IRAM space is relatively
24 #include <linux/module.h>
25 #include <linux/bitops.h>
26 #include <linux/i2c.h>
27 #include <linux/input.h>
28 #include <linux/interrupt.h>
29 #include <linux/kernel.h>
30 #include <linux/notifier.h>
31 #include <linux/platform_device.h>
32 #include <linux/slab.h>
33 #include <linux/input/matrix_keypad.h>
34 #include <linux/mfd/cros_ec.h>
35 #include <linux/mfd/cros_ec_commands.h>
38 * @rows: Number of rows in the keypad
39 * @cols: Number of columns in the keypad
40 * @row_shift: log2 or number of rows, rounded up
41 * @keymap_data: Matrix keymap data used to convert to keyscan values
42 * @ghost_filter: true to enable the matrix key-ghosting filter
43 * @valid_keys: bitmap of existing keys for each matrix column
44 * @old_kb_state: bitmap of keys pressed last scan
45 * @dev: Device pointer
47 * @ec: Top level ChromeOS device to use to talk to EC
48 * @notifier: interrupt event notifier for transport devices
54 const struct matrix_keymap_data *keymap_data;
57 uint8_t *old_kb_state;
60 struct input_dev *idev;
61 struct cros_ec_device *ec;
62 struct notifier_block notifier;
67 * Returns true when there is at least one combination of pressed keys that
68 * results in ghosting.
70 static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf)
72 int col1, col2, buf1, buf2;
73 struct device *dev = ckdev->dev;
74 uint8_t *valid_keys = ckdev->valid_keys;
77 * Ghosting happens if for any pressed key X there are other keys
78 * pressed both in the same row and column of X as, for instance,
79 * in the following diagram:
86 * In this case only X, Y, and Z are pressed, but g appears to be
87 * pressed too (see Wikipedia).
89 for (col1 = 0; col1 < ckdev->cols; col1++) {
90 buf1 = buf[col1] & valid_keys[col1];
91 for (col2 = col1 + 1; col2 < ckdev->cols; col2++) {
92 buf2 = buf[col2] & valid_keys[col2];
93 if (hweight8(buf1 & buf2) > 1) {
94 dev_dbg(dev, "ghost found at: B[%02d]:0x%02x & B[%02d]:0x%02x",
95 col1, buf1, col2, buf2);
106 * Compares the new keyboard state to the old one and produces key
107 * press/release events accordingly. The keyboard state is 13 bytes (one byte
110 static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev,
111 uint8_t *kb_state, int len)
113 struct input_dev *idev = ckdev->idev;
121 if (ckdev->ghost_filter && cros_ec_keyb_has_ghosting(ckdev, kb_state)) {
123 * Simple-minded solution: ignore this state. The obvious
124 * improvement is to only ignore changes to keys involved in
125 * the ghosting, but process the other changes.
127 dev_dbg(ckdev->dev, "ghosting found\n");
131 for (col = 0; col < ckdev->cols; col++) {
132 for (row = 0; row < ckdev->rows; row++) {
133 int pos = MATRIX_SCAN_CODE(row, col, ckdev->row_shift);
134 const unsigned short *keycodes = idev->keycode;
136 new_state = kb_state[col] & (1 << row);
137 old_state = ckdev->old_kb_state[col] & (1 << row);
138 if (new_state != old_state) {
140 "changed: [r%d c%d]: byte %02x\n",
141 row, col, new_state);
143 input_event(idev, EV_MSC, MSC_SCAN, pos);
144 input_report_key(idev, keycodes[pos],
148 ckdev->old_kb_state[col] = kb_state[col];
150 input_sync(ckdev->idev);
153 static int cros_ec_keyb_open(struct input_dev *dev)
155 struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
157 return blocking_notifier_chain_register(&ckdev->ec->event_notifier,
161 static void cros_ec_keyb_close(struct input_dev *dev)
163 struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
165 blocking_notifier_chain_unregister(&ckdev->ec->event_notifier,
169 static int cros_ec_keyb_work(struct notifier_block *nb,
170 unsigned long queued_during_suspend, void *_notify)
172 struct cros_ec_keyb *ckdev = container_of(nb, struct cros_ec_keyb,
175 if (ckdev->ec->event_data.event_type != EC_MKBP_EVENT_KEY_MATRIX)
178 * If EC is not the wake source, discard key state changes during
181 if (queued_during_suspend)
183 if (ckdev->ec->event_size != ckdev->cols) {
185 "Discarded incomplete key matrix event.\n");
188 cros_ec_keyb_process(ckdev, ckdev->ec->event_data.data.key_matrix,
189 ckdev->ec->event_size);
194 * Walks keycodes flipping bit in buffer COLUMNS deep where bit is ROW. Used by
195 * ghosting logic to ignore NULL or virtual keys.
197 static void cros_ec_keyb_compute_valid_keys(struct cros_ec_keyb *ckdev)
200 int row_shift = ckdev->row_shift;
201 unsigned short *keymap = ckdev->idev->keycode;
204 BUG_ON(ckdev->idev->keycodesize != sizeof(*keymap));
206 for (col = 0; col < ckdev->cols; col++) {
207 for (row = 0; row < ckdev->rows; row++) {
208 code = keymap[MATRIX_SCAN_CODE(row, col, row_shift)];
209 if (code && (code != KEY_BATTERY))
210 ckdev->valid_keys[col] |= 1 << row;
212 dev_dbg(ckdev->dev, "valid_keys[%02d] = 0x%02x\n",
213 col, ckdev->valid_keys[col]);
217 static int cros_ec_keyb_probe(struct platform_device *pdev)
219 struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
220 struct device *dev = &pdev->dev;
221 struct cros_ec_keyb *ckdev;
222 struct input_dev *idev;
223 struct device_node *np;
226 np = pdev->dev.of_node;
230 ckdev = devm_kzalloc(dev, sizeof(*ckdev), GFP_KERNEL);
233 err = matrix_keypad_parse_of_params(dev, &ckdev->rows, &ckdev->cols);
237 ckdev->valid_keys = devm_kzalloc(dev, ckdev->cols, GFP_KERNEL);
238 if (!ckdev->valid_keys)
241 ckdev->old_kb_state = devm_kzalloc(dev, ckdev->cols, GFP_KERNEL);
242 if (!ckdev->old_kb_state)
245 idev = devm_input_allocate_device(dev);
250 ckdev->notifier.notifier_call = cros_ec_keyb_work;
252 dev_set_drvdata(dev, ckdev);
254 idev->name = CROS_EC_DEV_NAME;
255 idev->phys = ec->phys_name;
256 __set_bit(EV_REP, idev->evbit);
258 idev->id.bustype = BUS_VIRTUAL;
259 idev->id.version = 1;
260 idev->id.product = 0;
261 idev->dev.parent = dev;
262 idev->open = cros_ec_keyb_open;
263 idev->close = cros_ec_keyb_close;
265 ckdev->ghost_filter = of_property_read_bool(np,
266 "google,needs-ghost-filter");
268 err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols,
271 dev_err(dev, "cannot build key matrix\n");
275 ckdev->row_shift = get_count_order(ckdev->cols);
277 input_set_capability(idev, EV_MSC, MSC_SCAN);
278 input_set_drvdata(idev, ckdev);
280 cros_ec_keyb_compute_valid_keys(ckdev);
282 err = input_register_device(ckdev->idev);
284 dev_err(dev, "cannot register input device\n");
292 static const struct of_device_id cros_ec_keyb_of_match[] = {
293 { .compatible = "google,cros-ec-keyb" },
296 MODULE_DEVICE_TABLE(of, cros_ec_keyb_of_match);
299 static struct platform_driver cros_ec_keyb_driver = {
300 .probe = cros_ec_keyb_probe,
302 .name = "cros-ec-keyb",
303 .of_match_table = of_match_ptr(cros_ec_keyb_of_match),
307 module_platform_driver(cros_ec_keyb_driver);
309 MODULE_LICENSE("GPL");
310 MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
311 MODULE_ALIAS("platform:cros-ec-keyb");