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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/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>
 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  */
 46 struct cros_ec_keyb {
 47         unsigned int rows;
 48         unsigned int cols;
 49         int row_shift;
 50         const struct matrix_keymap_data *keymap_data;
 51         bool ghost_filter;
 52         uint8_t *old_kb_state;
 53 
 54         struct device *dev;
 55         struct input_dev *idev;
 56         struct cros_ec_device *ec;
 57 };
 58 
 59 
 60 static bool cros_ec_keyb_row_has_ghosting(struct cros_ec_keyb *ckdev,
 61                                           uint8_t *buf, int row)
 62 {
 63         int pressed_in_row = 0;
 64         int row_has_teeth = 0;
 65         int col, mask;
 66 
 67         mask = 1 << row;
 68         for (col = 0; col < ckdev->cols; col++) {
 69                 if (buf[col] & mask) {
 70                         pressed_in_row++;
 71                         row_has_teeth |= buf[col] & ~mask;
 72                         if (pressed_in_row > 1 && row_has_teeth) {
 73                                 /* ghosting */
 74                                 dev_dbg(ckdev->dev,
 75                                         "ghost found at: r%d c%d, pressed %d, teeth 0x%x\n",
 76                                         row, col, pressed_in_row,
 77                                         row_has_teeth);
 78                                 return true;
 79                         }
 80                 }
 81         }
 82 
 83         return false;
 84 }
 85 
 86 /*
 87  * Returns true when there is at least one combination of pressed keys that
 88  * results in ghosting.
 89  */
 90 static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf)
 91 {
 92         int row;
 93 
 94         /*
 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:
 98          *
 99          * . . Y . g .
100          * . . . . . .
101          * . . . . . .
102          * . . X . Z .
103          *
104          * In this case only X, Y, and Z are pressed, but g appears to be
105          * pressed too (see Wikipedia).
106          *
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.
116          *
117          * (*) This looks linear in the number of keys, but it's not.  We can
118          * cheat because the number of rows is small.
119          */
120         for (row = 0; row < ckdev->rows; row++)
121                 if (cros_ec_keyb_row_has_ghosting(ckdev, buf, row))
122                         return true;
123 
124         return false;
125 }
126 
127 /*
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
130  * per column)
131  */
132 static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev,
133                          uint8_t *kb_state, int len)
134 {
135         struct input_dev *idev = ckdev->idev;
136         int col, row;
137         int new_state;
138         int old_state;
139         int num_cols;
140 
141         num_cols = len;
142 
143         if (ckdev->ghost_filter && cros_ec_keyb_has_ghosting(ckdev, kb_state)) {
144                 /*
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.
148                  */
149                 dev_dbg(ckdev->dev, "ghosting found\n");
150                 return;
151         }
152 
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;
157 
158                         new_state = kb_state[col] & (1 << row);
159                         old_state = ckdev->old_kb_state[col] & (1 << row);
160                         if (new_state != old_state) {
161                                 dev_dbg(ckdev->dev,
162                                         "changed: [r%d c%d]: byte %02x\n",
163                                         row, col, new_state);
164 
165                                 input_report_key(idev, keycodes[pos],
166                                                  new_state);
167                         }
168                 }
169                 ckdev->old_kb_state[col] = kb_state[col];
170         }
171         input_sync(ckdev->idev);
172 }
173 
174 static int cros_ec_keyb_get_state(struct cros_ec_keyb *ckdev, uint8_t *kb_state)
175 {
176         struct cros_ec_command msg = {
177                 .version = 0,
178                 .command = EC_CMD_MKBP_STATE,
179                 .outdata = NULL,
180                 .outsize = 0,
181                 .indata = kb_state,
182                 .insize = ckdev->cols,
183         };
184 
185         return ckdev->ec->cmd_xfer(ckdev->ec, &msg);
186 }
187 
188 static irqreturn_t cros_ec_keyb_irq(int irq, void *data)
189 {
190         struct cros_ec_keyb *ckdev = data;
191         struct cros_ec_device *ec = ckdev->ec;
192         int ret;
193         uint8_t kb_state[ckdev->cols];
194 
195         if (device_may_wakeup(ec->dev))
196                 pm_wakeup_event(ec->dev, 0);
197 
198         ret = cros_ec_keyb_get_state(ckdev, kb_state);
199         if (ret >= 0)
200                 cros_ec_keyb_process(ckdev, kb_state, ret);
201         else
202                 dev_err(ec->dev, "failed to get keyboard state: %d\n", ret);
203 
204         return IRQ_HANDLED;
205 }
206 
207 static int cros_ec_keyb_open(struct input_dev *dev)
208 {
209         struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
210         struct cros_ec_device *ec = ckdev->ec;
211 
212         return request_threaded_irq(ec->irq, NULL, cros_ec_keyb_irq,
213                                         IRQF_TRIGGER_LOW | IRQF_ONESHOT,
214                                         "cros_ec_keyb", ckdev);
215 }
216 
217 static void cros_ec_keyb_close(struct input_dev *dev)
218 {
219         struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
220         struct cros_ec_device *ec = ckdev->ec;
221 
222         free_irq(ec->irq, ckdev);
223 }
224 
225 static int cros_ec_keyb_probe(struct platform_device *pdev)
226 {
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;
232         int err;
233 
234         np = pdev->dev.of_node;
235         if (!np)
236                 return -ENODEV;
237 
238         ckdev = devm_kzalloc(&pdev->dev, sizeof(*ckdev), GFP_KERNEL);
239         if (!ckdev)
240                 return -ENOMEM;
241         err = matrix_keypad_parse_of_params(&pdev->dev, &ckdev->rows,
242                                             &ckdev->cols);
243         if (err)
244                 return err;
245         ckdev->old_kb_state = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
246         if (!ckdev->old_kb_state)
247                 return -ENOMEM;
248 
249         idev = devm_input_allocate_device(&pdev->dev);
250         if (!idev)
251                 return -ENOMEM;
252 
253         if (!ec->irq) {
254                 dev_err(dev, "no EC IRQ specified\n");
255                 return -EINVAL;
256         }
257 
258         ckdev->ec = ec;
259         ckdev->dev = dev;
260         dev_set_drvdata(&pdev->dev, ckdev);
261 
262         idev->name = ec->ec_name;
263         idev->phys = ec->phys_name;
264         __set_bit(EV_REP, idev->evbit);
265 
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;
272 
273         ckdev->ghost_filter = of_property_read_bool(np,
274                                         "google,needs-ghost-filter");
275 
276         err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols,
277                                          NULL, idev);
278         if (err) {
279                 dev_err(dev, "cannot build key matrix\n");
280                 return err;
281         }
282 
283         ckdev->row_shift = get_count_order(ckdev->cols);
284 
285         input_set_capability(idev, EV_MSC, MSC_SCAN);
286         input_set_drvdata(idev, ckdev);
287         ckdev->idev = idev;
288         err = input_register_device(ckdev->idev);
289         if (err) {
290                 dev_err(dev, "cannot register input device\n");
291                 return err;
292         }
293 
294         return 0;
295 }
296 
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)
300 {
301         uint8_t old_state[ckdev->cols];
302         uint8_t new_state[ckdev->cols];
303         unsigned long duration;
304         int i, ret;
305 
306         /*
307          * Keep reading until we see that the scan state does not change.
308          * That indicates that we are done.
309          *
310          * Assume that the EC keyscan buffer is at most 32 deep.
311          */
312         duration = jiffies;
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)))
318                         break;
319         }
320         duration = jiffies - duration;
321         dev_info(ckdev->dev, "Discarded %d keyscan(s) in %dus\n", i,
322                 jiffies_to_usecs(duration));
323 }
324 
325 static int cros_ec_keyb_resume(struct device *dev)
326 {
327         struct cros_ec_keyb *ckdev = dev_get_drvdata(dev);
328 
329         /*
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.
334          */
335         if (ckdev->ec->was_wake_device)
336                 cros_ec_keyb_clear_keyboard(ckdev);
337 
338         return 0;
339 }
340 
341 #endif
342 
343 static SIMPLE_DEV_PM_OPS(cros_ec_keyb_pm_ops, NULL, cros_ec_keyb_resume);
344 
345 static struct platform_driver cros_ec_keyb_driver = {
346         .probe = cros_ec_keyb_probe,
347         .driver = {
348                 .name = "cros-ec-keyb",
349                 .pm     = &cros_ec_keyb_pm_ops,
350         },
351 };
352 
353 module_platform_driver(cros_ec_keyb_driver);
354 
355 MODULE_LICENSE("GPL");
356 MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
357 MODULE_ALIAS("platform:cros-ec-keyb");
358 

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