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"); 335