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Linux/drivers/input/keyboard/cros_ec_keyb.c

  1 /*
  2  * ChromeOS EC keyboard driver
  3  *
  4  * Copyright (C) 2012 Google, Inc
  5  *
  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.
  9  *
 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.
 14  *
 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
 21  * expensive.
 22  */
 23 
 24 #include <linux/module.h>
 25 #include <linux/i2c.h>
 26 #include <linux/input.h>
 27 #include <linux/kernel.h>
 28 #include <linux/notifier.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>
 34 
 35 /*
 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
 43  * @idev: Input device
 44  * @ec: Top level ChromeOS device to use to talk to EC
 45  * @event_notifier: interrupt event notifier for transport devices
 46  */
 47 struct cros_ec_keyb {
 48         unsigned int rows;
 49         unsigned int cols;
 50         int row_shift;
 51         const struct matrix_keymap_data *keymap_data;
 52         bool ghost_filter;
 53         uint8_t *old_kb_state;
 54 
 55         struct device *dev;
 56         struct input_dev *idev;
 57         struct cros_ec_device *ec;
 58         struct notifier_block notifier;
 59 };
 60 
 61 
 62 static bool cros_ec_keyb_row_has_ghosting(struct cros_ec_keyb *ckdev,
 63                                           uint8_t *buf, int row)
 64 {
 65         int pressed_in_row = 0;
 66         int row_has_teeth = 0;
 67         int col, mask;
 68 
 69         mask = 1 << row;
 70         for (col = 0; col < ckdev->cols; col++) {
 71                 if (buf[col] & mask) {
 72                         pressed_in_row++;
 73                         row_has_teeth |= buf[col] & ~mask;
 74                         if (pressed_in_row > 1 && row_has_teeth) {
 75                                 /* ghosting */
 76                                 dev_dbg(ckdev->dev,
 77                                         "ghost found at: r%d c%d, pressed %d, teeth 0x%x\n",
 78                                         row, col, pressed_in_row,
 79                                         row_has_teeth);
 80                                 return true;
 81                         }
 82                 }
 83         }
 84 
 85         return false;
 86 }
 87 
 88 /*
 89  * Returns true when there is at least one combination of pressed keys that
 90  * results in ghosting.
 91  */
 92 static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf)
 93 {
 94         int row;
 95 
 96         /*
 97          * Ghosting happens if for any pressed key X there are other keys
 98          * pressed both in the same row and column of X as, for instance,
 99          * in the following diagram:
100          *
101          * . . Y . g .
102          * . . . . . .
103          * . . . . . .
104          * . . X . Z .
105          *
106          * In this case only X, Y, and Z are pressed, but g appears to be
107          * pressed too (see Wikipedia).
108          *
109          * We can detect ghosting in a single pass (*) over the keyboard state
110          * by maintaining two arrays.  pressed_in_row counts how many pressed
111          * keys we have found in a row.  row_has_teeth is true if any of the
112          * pressed keys for this row has other pressed keys in its column.  If
113          * at any point of the scan we find that a row has multiple pressed
114          * keys, and at least one of them is at the intersection with a column
115          * with multiple pressed keys, we're sure there is ghosting.
116          * Conversely, if there is ghosting, we will detect such situation for
117          * at least one key during the pass.
118          *
119          * (*) This looks linear in the number of keys, but it's not.  We can
120          * cheat because the number of rows is small.
121          */
122         for (row = 0; row < ckdev->rows; row++)
123                 if (cros_ec_keyb_row_has_ghosting(ckdev, buf, row))
124                         return true;
125 
126         return false;
127 }
128 
129 /*
130  * Compares the new keyboard state to the old one and produces key
131  * press/release events accordingly.  The keyboard state is 13 bytes (one byte
132  * per column)
133  */
134 static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev,
135                          uint8_t *kb_state, int len)
136 {
137         struct input_dev *idev = ckdev->idev;
138         int col, row;
139         int new_state;
140         int old_state;
141         int num_cols;
142 
143         num_cols = len;
144 
145         if (ckdev->ghost_filter && cros_ec_keyb_has_ghosting(ckdev, kb_state)) {
146                 /*
147                  * Simple-minded solution: ignore this state. The obvious
148                  * improvement is to only ignore changes to keys involved in
149                  * the ghosting, but process the other changes.
150                  */
151                 dev_dbg(ckdev->dev, "ghosting found\n");
152                 return;
153         }
154 
155         for (col = 0; col < ckdev->cols; col++) {
156                 for (row = 0; row < ckdev->rows; row++) {
157                         int pos = MATRIX_SCAN_CODE(row, col, ckdev->row_shift);
158                         const unsigned short *keycodes = idev->keycode;
159 
160                         new_state = kb_state[col] & (1 << row);
161                         old_state = ckdev->old_kb_state[col] & (1 << row);
162                         if (new_state != old_state) {
163                                 dev_dbg(ckdev->dev,
164                                         "changed: [r%d c%d]: byte %02x\n",
165                                         row, col, new_state);
166 
167                                 input_report_key(idev, keycodes[pos],
168                                                  new_state);
169                         }
170                 }
171                 ckdev->old_kb_state[col] = kb_state[col];
172         }
173         input_sync(ckdev->idev);
174 }
175 
176 static int cros_ec_keyb_open(struct input_dev *dev)
177 {
178         struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
179 
180         return blocking_notifier_chain_register(&ckdev->ec->event_notifier,
181                                                 &ckdev->notifier);
182 }
183 
184 static void cros_ec_keyb_close(struct input_dev *dev)
185 {
186         struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
187 
188         blocking_notifier_chain_unregister(&ckdev->ec->event_notifier,
189                                            &ckdev->notifier);
190 }
191 
192 static int cros_ec_keyb_get_state(struct cros_ec_keyb *ckdev, uint8_t *kb_state)
193 {
194         return ckdev->ec->command_recv(ckdev->ec, EC_CMD_MKBP_STATE,
195                                           kb_state, ckdev->cols);
196 }
197 
198 static int cros_ec_keyb_work(struct notifier_block *nb,
199                      unsigned long state, void *_notify)
200 {
201         int ret;
202         struct cros_ec_keyb *ckdev = container_of(nb, struct cros_ec_keyb,
203                                                     notifier);
204         uint8_t kb_state[ckdev->cols];
205 
206         ret = cros_ec_keyb_get_state(ckdev, kb_state);
207         if (ret >= 0)
208                 cros_ec_keyb_process(ckdev, kb_state, ret);
209 
210         return NOTIFY_DONE;
211 }
212 
213 static int cros_ec_keyb_probe(struct platform_device *pdev)
214 {
215         struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
216         struct device *dev = ec->dev;
217         struct cros_ec_keyb *ckdev;
218         struct input_dev *idev;
219         struct device_node *np;
220         int err;
221 
222         np = pdev->dev.of_node;
223         if (!np)
224                 return -ENODEV;
225 
226         ckdev = devm_kzalloc(&pdev->dev, sizeof(*ckdev), GFP_KERNEL);
227         if (!ckdev)
228                 return -ENOMEM;
229         err = matrix_keypad_parse_of_params(&pdev->dev, &ckdev->rows,
230                                             &ckdev->cols);
231         if (err)
232                 return err;
233         ckdev->old_kb_state = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
234         if (!ckdev->old_kb_state)
235                 return -ENOMEM;
236 
237         idev = devm_input_allocate_device(&pdev->dev);
238         if (!idev)
239                 return -ENOMEM;
240 
241         ckdev->ec = ec;
242         ckdev->notifier.notifier_call = cros_ec_keyb_work;
243         ckdev->dev = dev;
244         dev_set_drvdata(&pdev->dev, ckdev);
245 
246         idev->name = ec->ec_name;
247         idev->phys = ec->phys_name;
248         __set_bit(EV_REP, idev->evbit);
249 
250         idev->id.bustype = BUS_VIRTUAL;
251         idev->id.version = 1;
252         idev->id.product = 0;
253         idev->dev.parent = &pdev->dev;
254         idev->open = cros_ec_keyb_open;
255         idev->close = cros_ec_keyb_close;
256 
257         ckdev->ghost_filter = of_property_read_bool(np,
258                                         "google,needs-ghost-filter");
259 
260         err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols,
261                                          NULL, idev);
262         if (err) {
263                 dev_err(dev, "cannot build key matrix\n");
264                 return err;
265         }
266 
267         ckdev->row_shift = get_count_order(ckdev->cols);
268 
269         input_set_capability(idev, EV_MSC, MSC_SCAN);
270         input_set_drvdata(idev, ckdev);
271         ckdev->idev = idev;
272         err = input_register_device(ckdev->idev);
273         if (err) {
274                 dev_err(dev, "cannot register input device\n");
275                 return err;
276         }
277 
278         return 0;
279 }
280 
281 #ifdef CONFIG_PM_SLEEP
282 /* Clear any keys in the buffer */
283 static void cros_ec_keyb_clear_keyboard(struct cros_ec_keyb *ckdev)
284 {
285         uint8_t old_state[ckdev->cols];
286         uint8_t new_state[ckdev->cols];
287         unsigned long duration;
288         int i, ret;
289 
290         /*
291          * Keep reading until we see that the scan state does not change.
292          * That indicates that we are done.
293          *
294          * Assume that the EC keyscan buffer is at most 32 deep.
295          */
296         duration = jiffies;
297         ret = cros_ec_keyb_get_state(ckdev, new_state);
298         for (i = 1; !ret && i < 32; i++) {
299                 memcpy(old_state, new_state, sizeof(old_state));
300                 ret = cros_ec_keyb_get_state(ckdev, new_state);
301                 if (0 == memcmp(old_state, new_state, sizeof(old_state)))
302                         break;
303         }
304         duration = jiffies - duration;
305         dev_info(ckdev->dev, "Discarded %d keyscan(s) in %dus\n", i,
306                 jiffies_to_usecs(duration));
307 }
308 
309 static int cros_ec_keyb_resume(struct device *dev)
310 {
311         struct cros_ec_keyb *ckdev = dev_get_drvdata(dev);
312 
313         /*
314          * When the EC is not a wake source, then it could not have caused the
315          * resume, so we clear the EC's key scan buffer. If the EC was a
316          * wake source (e.g. the lid is open and the user might press a key to
317          * wake) then the key scan buffer should be preserved.
318          */
319         if (ckdev->ec->was_wake_device)
320                 cros_ec_keyb_clear_keyboard(ckdev);
321 
322         return 0;
323 }
324 
325 #endif
326 
327 static SIMPLE_DEV_PM_OPS(cros_ec_keyb_pm_ops, NULL, cros_ec_keyb_resume);
328 
329 static struct platform_driver cros_ec_keyb_driver = {
330         .probe = cros_ec_keyb_probe,
331         .driver = {
332                 .name = "cros-ec-keyb",
333                 .pm     = &cros_ec_keyb_pm_ops,
334         },
335 };
336 
337 module_platform_driver(cros_ec_keyb_driver);
338 
339 MODULE_LICENSE("GPL");
340 MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
341 MODULE_ALIAS("platform:cros-ec-keyb");
342 

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