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"); 342