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");