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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/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>
 36 
 37 /*
 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
 46  * @idev: Input device
 47  * @ec: Top level ChromeOS device to use to talk to EC
 48  * @notifier: interrupt event notifier for transport devices
 49  */
 50 struct cros_ec_keyb {
 51         unsigned int rows;
 52         unsigned int cols;
 53         int row_shift;
 54         const struct matrix_keymap_data *keymap_data;
 55         bool ghost_filter;
 56         uint8_t *valid_keys;
 57         uint8_t *old_kb_state;
 58 
 59         struct device *dev;
 60         struct input_dev *idev;
 61         struct cros_ec_device *ec;
 62         struct notifier_block notifier;
 63 };
 64 
 65 
 66 /*
 67  * Returns true when there is at least one combination of pressed keys that
 68  * results in ghosting.
 69  */
 70 static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf)
 71 {
 72         int col1, col2, buf1, buf2;
 73         struct device *dev = ckdev->dev;
 74         uint8_t *valid_keys = ckdev->valid_keys;
 75 
 76         /*
 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:
 80          *
 81          * . . Y . g .
 82          * . . . . . .
 83          * . . . . . .
 84          * . . X . Z .
 85          *
 86          * In this case only X, Y, and Z are pressed, but g appears to be
 87          * pressed too (see Wikipedia).
 88          */
 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);
 96                                 return true;
 97                         }
 98                 }
 99         }
100 
101         return false;
102 }
103 
104 
105 /*
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
108  * per column)
109  */
110 static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev,
111                          uint8_t *kb_state, int len)
112 {
113         struct input_dev *idev = ckdev->idev;
114         int col, row;
115         int new_state;
116         int old_state;
117         int num_cols;
118 
119         num_cols = len;
120 
121         if (ckdev->ghost_filter && cros_ec_keyb_has_ghosting(ckdev, kb_state)) {
122                 /*
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.
126                  */
127                 dev_dbg(ckdev->dev, "ghosting found\n");
128                 return;
129         }
130 
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;
135 
136                         new_state = kb_state[col] & (1 << row);
137                         old_state = ckdev->old_kb_state[col] & (1 << row);
138                         if (new_state != old_state) {
139                                 dev_dbg(ckdev->dev,
140                                         "changed: [r%d c%d]: byte %02x\n",
141                                         row, col, new_state);
142 
143                                 input_report_key(idev, keycodes[pos],
144                                                  new_state);
145                         }
146                 }
147                 ckdev->old_kb_state[col] = kb_state[col];
148         }
149         input_sync(ckdev->idev);
150 }
151 
152 static int cros_ec_keyb_open(struct input_dev *dev)
153 {
154         struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
155 
156         return blocking_notifier_chain_register(&ckdev->ec->event_notifier,
157                                                 &ckdev->notifier);
158 }
159 
160 static void cros_ec_keyb_close(struct input_dev *dev)
161 {
162         struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
163 
164         blocking_notifier_chain_unregister(&ckdev->ec->event_notifier,
165                                            &ckdev->notifier);
166 }
167 
168 static int cros_ec_keyb_work(struct notifier_block *nb,
169                              unsigned long queued_during_suspend, void *_notify)
170 {
171         struct cros_ec_keyb *ckdev = container_of(nb, struct cros_ec_keyb,
172                                                   notifier);
173 
174         if (ckdev->ec->event_data.event_type != EC_MKBP_EVENT_KEY_MATRIX)
175                 return NOTIFY_DONE;
176         /*
177          * If EC is not the wake source, discard key state changes during
178          * suspend.
179          */
180         if (queued_during_suspend)
181                 return NOTIFY_OK;
182         if (ckdev->ec->event_size != ckdev->cols) {
183                 dev_err(ckdev->dev,
184                         "Discarded incomplete key matrix event.\n");
185                 return NOTIFY_OK;
186         }
187         cros_ec_keyb_process(ckdev, ckdev->ec->event_data.data.key_matrix,
188                              ckdev->ec->event_size);
189         return NOTIFY_OK;
190 }
191 
192 /*
193  * Walks keycodes flipping bit in buffer COLUMNS deep where bit is ROW.  Used by
194  * ghosting logic to ignore NULL or virtual keys.
195  */
196 static void cros_ec_keyb_compute_valid_keys(struct cros_ec_keyb *ckdev)
197 {
198         int row, col;
199         int row_shift = ckdev->row_shift;
200         unsigned short *keymap = ckdev->idev->keycode;
201         unsigned short code;
202 
203         BUG_ON(ckdev->idev->keycodesize != sizeof(*keymap));
204 
205         for (col = 0; col < ckdev->cols; col++) {
206                 for (row = 0; row < ckdev->rows; row++) {
207                         code = keymap[MATRIX_SCAN_CODE(row, col, row_shift)];
208                         if (code && (code != KEY_BATTERY))
209                                 ckdev->valid_keys[col] |= 1 << row;
210                 }
211                 dev_dbg(ckdev->dev, "valid_keys[%02d] = 0x%02x\n",
212                         col, ckdev->valid_keys[col]);
213         }
214 }
215 
216 static int cros_ec_keyb_probe(struct platform_device *pdev)
217 {
218         struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
219         struct device *dev = &pdev->dev;
220         struct cros_ec_keyb *ckdev;
221         struct input_dev *idev;
222         struct device_node *np;
223         int err;
224 
225         np = pdev->dev.of_node;
226         if (!np)
227                 return -ENODEV;
228 
229         ckdev = devm_kzalloc(dev, sizeof(*ckdev), GFP_KERNEL);
230         if (!ckdev)
231                 return -ENOMEM;
232         err = matrix_keypad_parse_of_params(dev, &ckdev->rows, &ckdev->cols);
233         if (err)
234                 return err;
235 
236         ckdev->valid_keys = devm_kzalloc(dev, ckdev->cols, GFP_KERNEL);
237         if (!ckdev->valid_keys)
238                 return -ENOMEM;
239 
240         ckdev->old_kb_state = devm_kzalloc(dev, ckdev->cols, GFP_KERNEL);
241         if (!ckdev->old_kb_state)
242                 return -ENOMEM;
243 
244         idev = devm_input_allocate_device(dev);
245         if (!idev)
246                 return -ENOMEM;
247 
248         ckdev->ec = ec;
249         ckdev->notifier.notifier_call = cros_ec_keyb_work;
250         ckdev->dev = dev;
251         dev_set_drvdata(dev, ckdev);
252 
253         idev->name = CROS_EC_DEV_NAME;
254         idev->phys = ec->phys_name;
255         __set_bit(EV_REP, idev->evbit);
256 
257         idev->id.bustype = BUS_VIRTUAL;
258         idev->id.version = 1;
259         idev->id.product = 0;
260         idev->dev.parent = dev;
261         idev->open = cros_ec_keyb_open;
262         idev->close = cros_ec_keyb_close;
263 
264         ckdev->ghost_filter = of_property_read_bool(np,
265                                         "google,needs-ghost-filter");
266 
267         err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols,
268                                          NULL, idev);
269         if (err) {
270                 dev_err(dev, "cannot build key matrix\n");
271                 return err;
272         }
273 
274         ckdev->row_shift = get_count_order(ckdev->cols);
275 
276         input_set_capability(idev, EV_MSC, MSC_SCAN);
277         input_set_drvdata(idev, ckdev);
278         ckdev->idev = idev;
279         cros_ec_keyb_compute_valid_keys(ckdev);
280 
281         err = input_register_device(ckdev->idev);
282         if (err) {
283                 dev_err(dev, "cannot register input device\n");
284                 return err;
285         }
286 
287         return 0;
288 }
289 
290 #ifdef CONFIG_OF
291 static const struct of_device_id cros_ec_keyb_of_match[] = {
292         { .compatible = "google,cros-ec-keyb" },
293         {},
294 };
295 MODULE_DEVICE_TABLE(of, cros_ec_keyb_of_match);
296 #endif
297 
298 static struct platform_driver cros_ec_keyb_driver = {
299         .probe = cros_ec_keyb_probe,
300         .driver = {
301                 .name = "cros-ec-keyb",
302                 .of_match_table = of_match_ptr(cros_ec_keyb_of_match),
303         },
304 };
305 
306 module_platform_driver(cros_ec_keyb_driver);
307 
308 MODULE_LICENSE("GPL");
309 MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
310 MODULE_ALIAS("platform:cros-ec-keyb");
311 

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