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/i2c.h>
26 #include <linux/input.h>
27 #include <linux/interrupt.h>
28 #include <linux/kernel.h>
29 #include <linux/platform_device.h>
30 #include <linux/slab.h>
31 #include <linux/input/matrix_keypad.h>
32 #include <linux/mfd/cros_ec.h>
33 #include <linux/mfd/cros_ec_commands.h>
36 * @rows: Number of rows in the keypad
37 * @cols: Number of columns in the keypad
38 * @row_shift: log2 or number of rows, rounded up
39 * @keymap_data: Matrix keymap data used to convert to keyscan values
40 * @ghost_filter: true to enable the matrix key-ghosting filter
41 * @old_kb_state: bitmap of keys pressed last scan
42 * @dev: Device pointer
44 * @ec: Top level ChromeOS device to use to talk to EC
50 const struct matrix_keymap_data *keymap_data;
52 uint8_t *old_kb_state;
55 struct input_dev *idev;
56 struct cros_ec_device *ec;
60 static bool cros_ec_keyb_row_has_ghosting(struct cros_ec_keyb *ckdev,
61 uint8_t *buf, int row)
63 int pressed_in_row = 0;
64 int row_has_teeth = 0;
68 for (col = 0; col < ckdev->cols; col++) {
69 if (buf[col] & mask) {
71 row_has_teeth |= buf[col] & ~mask;
72 if (pressed_in_row > 1 && row_has_teeth) {
75 "ghost found at: r%d c%d, pressed %d, teeth 0x%x\n",
76 row, col, pressed_in_row,
87 * Returns true when there is at least one combination of pressed keys that
88 * results in ghosting.
90 static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf)
95 * Ghosting happens if for any pressed key X there are other keys
96 * pressed both in the same row and column of X as, for instance,
97 * in the following diagram:
104 * In this case only X, Y, and Z are pressed, but g appears to be
105 * pressed too (see Wikipedia).
107 * We can detect ghosting in a single pass (*) over the keyboard state
108 * by maintaining two arrays. pressed_in_row counts how many pressed
109 * keys we have found in a row. row_has_teeth is true if any of the
110 * pressed keys for this row has other pressed keys in its column. If
111 * at any point of the scan we find that a row has multiple pressed
112 * keys, and at least one of them is at the intersection with a column
113 * with multiple pressed keys, we're sure there is ghosting.
114 * Conversely, if there is ghosting, we will detect such situation for
115 * at least one key during the pass.
117 * (*) This looks linear in the number of keys, but it's not. We can
118 * cheat because the number of rows is small.
120 for (row = 0; row < ckdev->rows; row++)
121 if (cros_ec_keyb_row_has_ghosting(ckdev, buf, row))
128 * Compares the new keyboard state to the old one and produces key
129 * press/release events accordingly. The keyboard state is 13 bytes (one byte
132 static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev,
133 uint8_t *kb_state, int len)
135 struct input_dev *idev = ckdev->idev;
143 if (ckdev->ghost_filter && cros_ec_keyb_has_ghosting(ckdev, kb_state)) {
145 * Simple-minded solution: ignore this state. The obvious
146 * improvement is to only ignore changes to keys involved in
147 * the ghosting, but process the other changes.
149 dev_dbg(ckdev->dev, "ghosting found\n");
153 for (col = 0; col < ckdev->cols; col++) {
154 for (row = 0; row < ckdev->rows; row++) {
155 int pos = MATRIX_SCAN_CODE(row, col, ckdev->row_shift);
156 const unsigned short *keycodes = idev->keycode;
158 new_state = kb_state[col] & (1 << row);
159 old_state = ckdev->old_kb_state[col] & (1 << row);
160 if (new_state != old_state) {
162 "changed: [r%d c%d]: byte %02x\n",
163 row, col, new_state);
165 input_report_key(idev, keycodes[pos],
169 ckdev->old_kb_state[col] = kb_state[col];
171 input_sync(ckdev->idev);
174 static int cros_ec_keyb_get_state(struct cros_ec_keyb *ckdev, uint8_t *kb_state)
176 struct cros_ec_command msg = {
178 .command = EC_CMD_MKBP_STATE,
182 .insize = ckdev->cols,
185 return ckdev->ec->cmd_xfer(ckdev->ec, &msg);
188 static irqreturn_t cros_ec_keyb_irq(int irq, void *data)
190 struct cros_ec_keyb *ckdev = data;
191 struct cros_ec_device *ec = ckdev->ec;
193 uint8_t kb_state[ckdev->cols];
195 if (device_may_wakeup(ec->dev))
196 pm_wakeup_event(ec->dev, 0);
198 ret = cros_ec_keyb_get_state(ckdev, kb_state);
200 cros_ec_keyb_process(ckdev, kb_state, ret);
202 dev_err(ec->dev, "failed to get keyboard state: %d\n", ret);
207 static int cros_ec_keyb_open(struct input_dev *dev)
209 struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
210 struct cros_ec_device *ec = ckdev->ec;
212 return request_threaded_irq(ec->irq, NULL, cros_ec_keyb_irq,
213 IRQF_TRIGGER_LOW | IRQF_ONESHOT,
214 "cros_ec_keyb", ckdev);
217 static void cros_ec_keyb_close(struct input_dev *dev)
219 struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
220 struct cros_ec_device *ec = ckdev->ec;
222 free_irq(ec->irq, ckdev);
225 static int cros_ec_keyb_probe(struct platform_device *pdev)
227 struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
228 struct device *dev = ec->dev;
229 struct cros_ec_keyb *ckdev;
230 struct input_dev *idev;
231 struct device_node *np;
234 np = pdev->dev.of_node;
238 ckdev = devm_kzalloc(&pdev->dev, sizeof(*ckdev), GFP_KERNEL);
241 err = matrix_keypad_parse_of_params(&pdev->dev, &ckdev->rows,
245 ckdev->old_kb_state = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
246 if (!ckdev->old_kb_state)
249 idev = devm_input_allocate_device(&pdev->dev);
254 dev_err(dev, "no EC IRQ specified\n");
260 dev_set_drvdata(&pdev->dev, ckdev);
262 idev->name = ec->ec_name;
263 idev->phys = ec->phys_name;
264 __set_bit(EV_REP, idev->evbit);
266 idev->id.bustype = BUS_VIRTUAL;
267 idev->id.version = 1;
268 idev->id.product = 0;
269 idev->dev.parent = &pdev->dev;
270 idev->open = cros_ec_keyb_open;
271 idev->close = cros_ec_keyb_close;
273 ckdev->ghost_filter = of_property_read_bool(np,
274 "google,needs-ghost-filter");
276 err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols,
279 dev_err(dev, "cannot build key matrix\n");
283 ckdev->row_shift = get_count_order(ckdev->cols);
285 input_set_capability(idev, EV_MSC, MSC_SCAN);
286 input_set_drvdata(idev, ckdev);
288 err = input_register_device(ckdev->idev);
290 dev_err(dev, "cannot register input device\n");
297 #ifdef CONFIG_PM_SLEEP
298 /* Clear any keys in the buffer */
299 static void cros_ec_keyb_clear_keyboard(struct cros_ec_keyb *ckdev)
301 uint8_t old_state[ckdev->cols];
302 uint8_t new_state[ckdev->cols];
303 unsigned long duration;
307 * Keep reading until we see that the scan state does not change.
308 * That indicates that we are done.
310 * Assume that the EC keyscan buffer is at most 32 deep.
313 ret = cros_ec_keyb_get_state(ckdev, new_state);
314 for (i = 1; !ret && i < 32; i++) {
315 memcpy(old_state, new_state, sizeof(old_state));
316 ret = cros_ec_keyb_get_state(ckdev, new_state);
317 if (0 == memcmp(old_state, new_state, sizeof(old_state)))
320 duration = jiffies - duration;
321 dev_info(ckdev->dev, "Discarded %d keyscan(s) in %dus\n", i,
322 jiffies_to_usecs(duration));
325 static int cros_ec_keyb_resume(struct device *dev)
327 struct cros_ec_keyb *ckdev = dev_get_drvdata(dev);
330 * When the EC is not a wake source, then it could not have caused the
331 * resume, so we clear the EC's key scan buffer. If the EC was a
332 * wake source (e.g. the lid is open and the user might press a key to
333 * wake) then the key scan buffer should be preserved.
335 if (ckdev->ec->was_wake_device)
336 cros_ec_keyb_clear_keyboard(ckdev);
343 static SIMPLE_DEV_PM_OPS(cros_ec_keyb_pm_ops, NULL, cros_ec_keyb_resume);
345 static struct platform_driver cros_ec_keyb_driver = {
346 .probe = cros_ec_keyb_probe,
348 .name = "cros-ec-keyb",
349 .pm = &cros_ec_keyb_pm_ops,
353 module_platform_driver(cros_ec_keyb_driver);
355 MODULE_LICENSE("GPL");
356 MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
357 MODULE_ALIAS("platform:cros-ec-keyb");