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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/platform_device.h>
 31 #include <linux/slab.h>
 32 #include <linux/input/matrix_keypad.h>
 33 #include <linux/mfd/cros_ec.h>
 34 #include <linux/mfd/cros_ec_commands.h>
 35 
 36 /*
 37  * @rows: Number of rows in the keypad
 38  * @cols: Number of columns in the keypad
 39  * @row_shift: log2 or number of rows, rounded up
 40  * @keymap_data: Matrix keymap data used to convert to keyscan values
 41  * @ghost_filter: true to enable the matrix key-ghosting filter
 42  * @valid_keys: bitmap of existing keys for each matrix column
 43  * @old_kb_state: bitmap of keys pressed last scan
 44  * @dev: Device pointer
 45  * @idev: Input device
 46  * @ec: Top level ChromeOS device to use to talk to EC
 47  */
 48 struct cros_ec_keyb {
 49         unsigned int rows;
 50         unsigned int cols;
 51         int row_shift;
 52         const struct matrix_keymap_data *keymap_data;
 53         bool ghost_filter;
 54         uint8_t *valid_keys;
 55         uint8_t *old_kb_state;
 56 
 57         struct device *dev;
 58         struct input_dev *idev;
 59         struct cros_ec_device *ec;
 60 };
 61 
 62 
 63 /*
 64  * Returns true when there is at least one combination of pressed keys that
 65  * results in ghosting.
 66  */
 67 static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf)
 68 {
 69         int col1, col2, buf1, buf2;
 70         struct device *dev = ckdev->dev;
 71         uint8_t *valid_keys = ckdev->valid_keys;
 72 
 73         /*
 74          * Ghosting happens if for any pressed key X there are other keys
 75          * pressed both in the same row and column of X as, for instance,
 76          * in the following diagram:
 77          *
 78          * . . Y . g .
 79          * . . . . . .
 80          * . . . . . .
 81          * . . X . Z .
 82          *
 83          * In this case only X, Y, and Z are pressed, but g appears to be
 84          * pressed too (see Wikipedia).
 85          */
 86         for (col1 = 0; col1 < ckdev->cols; col1++) {
 87                 buf1 = buf[col1] & valid_keys[col1];
 88                 for (col2 = col1 + 1; col2 < ckdev->cols; col2++) {
 89                         buf2 = buf[col2] & valid_keys[col2];
 90                         if (hweight8(buf1 & buf2) > 1) {
 91                                 dev_dbg(dev, "ghost found at: B[%02d]:0x%02x & B[%02d]:0x%02x",
 92                                         col1, buf1, col2, buf2);
 93                                 return true;
 94                         }
 95                 }
 96         }
 97 
 98         return false;
 99 }
100 
101 
102 /*
103  * Compares the new keyboard state to the old one and produces key
104  * press/release events accordingly.  The keyboard state is 13 bytes (one byte
105  * per column)
106  */
107 static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev,
108                          uint8_t *kb_state, int len)
109 {
110         struct input_dev *idev = ckdev->idev;
111         int col, row;
112         int new_state;
113         int old_state;
114         int num_cols;
115 
116         num_cols = len;
117 
118         if (ckdev->ghost_filter && cros_ec_keyb_has_ghosting(ckdev, kb_state)) {
119                 /*
120                  * Simple-minded solution: ignore this state. The obvious
121                  * improvement is to only ignore changes to keys involved in
122                  * the ghosting, but process the other changes.
123                  */
124                 dev_dbg(ckdev->dev, "ghosting found\n");
125                 return;
126         }
127 
128         for (col = 0; col < ckdev->cols; col++) {
129                 for (row = 0; row < ckdev->rows; row++) {
130                         int pos = MATRIX_SCAN_CODE(row, col, ckdev->row_shift);
131                         const unsigned short *keycodes = idev->keycode;
132 
133                         new_state = kb_state[col] & (1 << row);
134                         old_state = ckdev->old_kb_state[col] & (1 << row);
135                         if (new_state != old_state) {
136                                 dev_dbg(ckdev->dev,
137                                         "changed: [r%d c%d]: byte %02x\n",
138                                         row, col, new_state);
139 
140                                 input_report_key(idev, keycodes[pos],
141                                                  new_state);
142                         }
143                 }
144                 ckdev->old_kb_state[col] = kb_state[col];
145         }
146         input_sync(ckdev->idev);
147 }
148 
149 static int cros_ec_keyb_get_state(struct cros_ec_keyb *ckdev, uint8_t *kb_state)
150 {
151         int ret;
152         struct cros_ec_command msg = {
153                 .command = EC_CMD_MKBP_STATE,
154                 .insize = ckdev->cols,
155         };
156 
157         ret = cros_ec_cmd_xfer(ckdev->ec, &msg);
158         if (ret < 0)
159                 return ret;
160 
161         memcpy(kb_state, msg.indata, ckdev->cols);
162 
163         return 0;
164 }
165 
166 static irqreturn_t cros_ec_keyb_irq(int irq, void *data)
167 {
168         struct cros_ec_keyb *ckdev = data;
169         struct cros_ec_device *ec = ckdev->ec;
170         int ret;
171         uint8_t kb_state[ckdev->cols];
172 
173         if (device_may_wakeup(ec->dev))
174                 pm_wakeup_event(ec->dev, 0);
175 
176         ret = cros_ec_keyb_get_state(ckdev, kb_state);
177         if (ret >= 0)
178                 cros_ec_keyb_process(ckdev, kb_state, ret);
179         else
180                 dev_err(ec->dev, "failed to get keyboard state: %d\n", ret);
181 
182         return IRQ_HANDLED;
183 }
184 
185 static int cros_ec_keyb_open(struct input_dev *dev)
186 {
187         struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
188         struct cros_ec_device *ec = ckdev->ec;
189 
190         return request_threaded_irq(ec->irq, NULL, cros_ec_keyb_irq,
191                                         IRQF_TRIGGER_LOW | IRQF_ONESHOT,
192                                         "cros_ec_keyb", ckdev);
193 }
194 
195 static void cros_ec_keyb_close(struct input_dev *dev)
196 {
197         struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
198         struct cros_ec_device *ec = ckdev->ec;
199 
200         free_irq(ec->irq, ckdev);
201 }
202 
203 /*
204  * Walks keycodes flipping bit in buffer COLUMNS deep where bit is ROW.  Used by
205  * ghosting logic to ignore NULL or virtual keys.
206  */
207 static void cros_ec_keyb_compute_valid_keys(struct cros_ec_keyb *ckdev)
208 {
209         int row, col;
210         int row_shift = ckdev->row_shift;
211         unsigned short *keymap = ckdev->idev->keycode;
212         unsigned short code;
213 
214         BUG_ON(ckdev->idev->keycodesize != sizeof(*keymap));
215 
216         for (col = 0; col < ckdev->cols; col++) {
217                 for (row = 0; row < ckdev->rows; row++) {
218                         code = keymap[MATRIX_SCAN_CODE(row, col, row_shift)];
219                         if (code && (code != KEY_BATTERY))
220                                 ckdev->valid_keys[col] |= 1 << row;
221                 }
222                 dev_dbg(ckdev->dev, "valid_keys[%02d] = 0x%02x\n",
223                         col, ckdev->valid_keys[col]);
224         }
225 }
226 
227 static int cros_ec_keyb_probe(struct platform_device *pdev)
228 {
229         struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
230         struct device *dev = ec->dev;
231         struct cros_ec_keyb *ckdev;
232         struct input_dev *idev;
233         struct device_node *np;
234         int err;
235 
236         np = pdev->dev.of_node;
237         if (!np)
238                 return -ENODEV;
239 
240         ckdev = devm_kzalloc(&pdev->dev, sizeof(*ckdev), GFP_KERNEL);
241         if (!ckdev)
242                 return -ENOMEM;
243         err = matrix_keypad_parse_of_params(&pdev->dev, &ckdev->rows,
244                                             &ckdev->cols);
245         if (err)
246                 return err;
247 
248         ckdev->valid_keys = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
249         if (!ckdev->valid_keys)
250                 return -ENOMEM;
251 
252         ckdev->old_kb_state = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
253         if (!ckdev->old_kb_state)
254                 return -ENOMEM;
255 
256         idev = devm_input_allocate_device(&pdev->dev);
257         if (!idev)
258                 return -ENOMEM;
259 
260         if (!ec->irq) {
261                 dev_err(dev, "no EC IRQ specified\n");
262                 return -EINVAL;
263         }
264 
265         ckdev->ec = ec;
266         ckdev->dev = dev;
267         dev_set_drvdata(&pdev->dev, ckdev);
268 
269         idev->name = ec->ec_name;
270         idev->phys = ec->phys_name;
271         __set_bit(EV_REP, idev->evbit);
272 
273         idev->id.bustype = BUS_VIRTUAL;
274         idev->id.version = 1;
275         idev->id.product = 0;
276         idev->dev.parent = &pdev->dev;
277         idev->open = cros_ec_keyb_open;
278         idev->close = cros_ec_keyb_close;
279 
280         ckdev->ghost_filter = of_property_read_bool(np,
281                                         "google,needs-ghost-filter");
282 
283         err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols,
284                                          NULL, idev);
285         if (err) {
286                 dev_err(dev, "cannot build key matrix\n");
287                 return err;
288         }
289 
290         ckdev->row_shift = get_count_order(ckdev->cols);
291 
292         input_set_capability(idev, EV_MSC, MSC_SCAN);
293         input_set_drvdata(idev, ckdev);
294         ckdev->idev = idev;
295         cros_ec_keyb_compute_valid_keys(ckdev);
296 
297         err = input_register_device(ckdev->idev);
298         if (err) {
299                 dev_err(dev, "cannot register input device\n");
300                 return err;
301         }
302 
303         return 0;
304 }
305 
306 #ifdef CONFIG_PM_SLEEP
307 /* Clear any keys in the buffer */
308 static void cros_ec_keyb_clear_keyboard(struct cros_ec_keyb *ckdev)
309 {
310         uint8_t old_state[ckdev->cols];
311         uint8_t new_state[ckdev->cols];
312         unsigned long duration;
313         int i, ret;
314 
315         /*
316          * Keep reading until we see that the scan state does not change.
317          * That indicates that we are done.
318          *
319          * Assume that the EC keyscan buffer is at most 32 deep.
320          */
321         duration = jiffies;
322         ret = cros_ec_keyb_get_state(ckdev, new_state);
323         for (i = 1; !ret && i < 32; i++) {
324                 memcpy(old_state, new_state, sizeof(old_state));
325                 ret = cros_ec_keyb_get_state(ckdev, new_state);
326                 if (0 == memcmp(old_state, new_state, sizeof(old_state)))
327                         break;
328         }
329         duration = jiffies - duration;
330         dev_info(ckdev->dev, "Discarded %d keyscan(s) in %dus\n", i,
331                 jiffies_to_usecs(duration));
332 }
333 
334 static int cros_ec_keyb_resume(struct device *dev)
335 {
336         struct cros_ec_keyb *ckdev = dev_get_drvdata(dev);
337 
338         /*
339          * When the EC is not a wake source, then it could not have caused the
340          * resume, so we clear the EC's key scan buffer. If the EC was a
341          * wake source (e.g. the lid is open and the user might press a key to
342          * wake) then the key scan buffer should be preserved.
343          */
344         if (!ckdev->ec->was_wake_device)
345                 cros_ec_keyb_clear_keyboard(ckdev);
346 
347         return 0;
348 }
349 
350 #endif
351 
352 static SIMPLE_DEV_PM_OPS(cros_ec_keyb_pm_ops, NULL, cros_ec_keyb_resume);
353 
354 #ifdef CONFIG_OF
355 static const struct of_device_id cros_ec_keyb_of_match[] = {
356         { .compatible = "google,cros-ec-keyb" },
357         {},
358 };
359 MODULE_DEVICE_TABLE(of, cros_ec_keyb_of_match);
360 #endif
361 
362 static struct platform_driver cros_ec_keyb_driver = {
363         .probe = cros_ec_keyb_probe,
364         .driver = {
365                 .name = "cros-ec-keyb",
366                 .of_match_table = of_match_ptr(cros_ec_keyb_of_match),
367                 .pm     = &cros_ec_keyb_pm_ops,
368         },
369 };
370 
371 module_platform_driver(cros_ec_keyb_driver);
372 
373 MODULE_LICENSE("GPL");
374 MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
375 MODULE_ALIAS("platform:cros-ec-keyb");
376 

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