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");