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  * @dev: Device pointer
  42  * @idev: Input device
  43  * @ec: Top level ChromeOS device to use to talk to EC
  44  * @event_notifier: interrupt event notifier for transport devices
  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
  53         struct device *dev;
  54         struct input_dev *idev;
  55         struct cros_ec_device *ec;
  56         struct notifier_block notifier;
  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 num_cols;
 139
 140         num_cols = len;
 141
 142         if (ckdev->ghost_filter && cros_ec_keyb_has_ghosting(ckdev, kb_state)) {
 143                 /*
 144                  * Simple-minded solution: ignore this state. The obvious
 145                  * improvement is to only ignore changes to keys involved in
 146                  * the ghosting, but process the other changes.
 147                  */
 148                 dev_dbg(ckdev->dev, "ghosting found\n");
 149                 return;
 150         }
 151
 152         for (col = 0; col < ckdev->cols; col++) {
 153                 for (row = 0; row < ckdev->rows; row++) {
 154                         int pos = MATRIX_SCAN_CODE(row, col, ckdev->row_shift);
 155                         const unsigned short *keycodes = idev->keycode;
 156                         int code;
 157
 158                         code = keycodes[pos];
 159                         new_state = kb_state[col] & (1 << row);
 160                         if (!!new_state != test_bit(code, idev->key)) {
 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, code, new_state);
 166                         }
 167                 }
 168         }
 169         input_sync(ckdev->idev);
 170 }
 171
 172 static int cros_ec_keyb_open(struct input_dev *dev)
 173 {
 174         struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
 175
 176         return blocking_notifier_chain_register(&ckdev->ec->event_notifier,
 177                                                 &ckdev->notifier);
 178 }
 179
 180 static void cros_ec_keyb_close(struct input_dev *dev)
 181 {
 182         struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
 183
 184         blocking_notifier_chain_unregister(&ckdev->ec->event_notifier,
 185                                            &ckdev->notifier);
 186 }
 187
 188 static int cros_ec_keyb_get_state(struct cros_ec_keyb *ckdev, uint8_t *kb_state)
 189 {
 190         return ckdev->ec->command_recv(ckdev->ec, EC_CMD_MKBP_STATE,
 191                                           kb_state, ckdev->cols);
 192 }
 193
 194 static int cros_ec_keyb_work(struct notifier_block *nb,
 195                      unsigned long state, void *_notify)
 196 {
 197         int ret;
 198         struct cros_ec_keyb *ckdev = container_of(nb, struct cros_ec_keyb,
 199                                                     notifier);
 200         uint8_t kb_state[ckdev->cols];
 201
 202         ret = cros_ec_keyb_get_state(ckdev, kb_state);
 203         if (ret >= 0)
 204                 cros_ec_keyb_process(ckdev, kb_state, ret);
 205
 206         return NOTIFY_DONE;
 207 }
 208
 209 static int cros_ec_keyb_probe(struct platform_device *pdev)
 210 {
 211         struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
 212         struct device *dev = ec->dev;
 213         struct cros_ec_keyb *ckdev;
 214         struct input_dev *idev;
 215         struct device_node *np;
 216         int err;
 217
 218         np = pdev->dev.of_node;
 219         if (!np)
 220                 return -ENODEV;
 221
 222         ckdev = devm_kzalloc(&pdev->dev, sizeof(*ckdev), GFP_KERNEL);
 223         if (!ckdev)
 224                 return -ENOMEM;
 225         err = matrix_keypad_parse_of_params(&pdev->dev, &ckdev->rows,
 226                                             &ckdev->cols);
 227         if (err)
 228                 return err;
 229
 230         idev = devm_input_allocate_device(&pdev->dev);
 231         if (!idev)
 232                 return -ENOMEM;
 233
 234         ckdev->ec = ec;
 235         ckdev->notifier.notifier_call = cros_ec_keyb_work;
 236         ckdev->dev = dev;
 237         dev_set_drvdata(&pdev->dev, ckdev);
 238
 239         idev->name = ec->ec_name;
 240         idev->phys = ec->phys_name;
 241         __set_bit(EV_REP, idev->evbit);
 242
 243         idev->id.bustype = BUS_VIRTUAL;
 244         idev->id.version = 1;
 245         idev->id.product = 0;
 246         idev->dev.parent = &pdev->dev;
 247         idev->open = cros_ec_keyb_open;
 248         idev->close = cros_ec_keyb_close;
 249
 250         ckdev->ghost_filter = of_property_read_bool(np,
 251                                         "google,needs-ghost-filter");
 252
 253         err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols,
 254                                          NULL, idev);
 255         if (err) {
 256                 dev_err(dev, "cannot build key matrix\n");
 257                 return err;
 258         }
 259
 260         ckdev->row_shift = get_count_order(ckdev->cols);
 261
 262         input_set_capability(idev, EV_MSC, MSC_SCAN);
 263         input_set_drvdata(idev, ckdev);
 264         ckdev->idev = idev;
 265         err = input_register_device(ckdev->idev);
 266         if (err) {
 267                 dev_err(dev, "cannot register input device\n");
 268                 return err;
 269         }
 270
 271         return 0;
 272 }
 273
 274 #ifdef CONFIG_PM_SLEEP
 275 /* Clear any keys in the buffer */
 276 static void cros_ec_keyb_clear_keyboard(struct cros_ec_keyb *ckdev)
 277 {
 278         uint8_t old_state[ckdev->cols];
 279         uint8_t new_state[ckdev->cols];
 280         unsigned long duration;
 281         int i, ret;
 282
 283         /*
 284          * Keep reading until we see that the scan state does not change.
 285          * That indicates that we are done.
 286          *
 287          * Assume that the EC keyscan buffer is at most 32 deep.
 288          */
 289         duration = jiffies;
 290         ret = cros_ec_keyb_get_state(ckdev, new_state);
 291         for (i = 1; !ret && i < 32; i++) {
 292                 memcpy(old_state, new_state, sizeof(old_state));
 293                 ret = cros_ec_keyb_get_state(ckdev, new_state);
 294                 if (0 == memcmp(old_state, new_state, sizeof(old_state)))
 295                         break;
 296         }
 297         duration = jiffies - duration;
 298         dev_info(ckdev->dev, "Discarded %d keyscan(s) in %dus\n", i,
 299                 jiffies_to_usecs(duration));
 300 }
 301
 302 static int cros_ec_keyb_resume(struct device *dev)
 303 {
 304         struct cros_ec_keyb *ckdev = dev_get_drvdata(dev);
 305
 306         /*
 307          * When the EC is not a wake source, then it could not have caused the
 308          * resume, so we clear the EC's key scan buffer. If the EC was a
 309          * wake source (e.g. the lid is open and the user might press a key to
 310          * wake) then the key scan buffer should be preserved.
 311          */
 312         if (ckdev->ec->was_wake_device)
 313                 cros_ec_keyb_clear_keyboard(ckdev);
 314
 315         return 0;
 316 }
 317
 318 #endif
 319
 320 static SIMPLE_DEV_PM_OPS(cros_ec_keyb_pm_ops, NULL, cros_ec_keyb_resume);
 321
 322 static struct platform_driver cros_ec_keyb_driver = {
 323         .probe = cros_ec_keyb_probe,
 324         .driver = {
 325                 .name = "cros-ec-keyb",
 326                 .pm     = &cros_ec_keyb_pm_ops,
 327         },
 328 };
 329
 330 module_platform_driver(cros_ec_keyb_driver);
 331
 332 MODULE_LICENSE("GPL");
 333 MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
 334 MODULE_ALIAS("platform:cros-ec-keyb");