diff options
Diffstat (limited to 'drivers/input/keyboard/cros_ec_keyb.c')
| -rw-r--r-- | drivers/input/keyboard/cros_ec_keyb.c | 334 |
1 files changed, 334 insertions, 0 deletions
diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c new file mode 100644 index 000000000000..49557f27bfa6 --- /dev/null +++ b/drivers/input/keyboard/cros_ec_keyb.c @@ -0,0 +1,334 @@ +/* + * ChromeOS EC keyboard driver + * + * Copyright (C) 2012 Google, Inc + * + * This software is licensed under the terms of the GNU General Public + * License version 2, as published by the Free Software Foundation, and + * may be copied, distributed, and modified under those terms. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * This driver uses the Chrome OS EC byte-level message-based protocol for + * communicating the keyboard state (which keys are pressed) from a keyboard EC + * to the AP over some bus (such as i2c, lpc, spi). The EC does debouncing, + * but everything else (including deghosting) is done here. The main + * motivation for this is to keep the EC firmware as simple as possible, since + * it cannot be easily upgraded and EC flash/IRAM space is relatively + * expensive. + */ + +#include <linux/module.h> +#include <linux/i2c.h> +#include <linux/input.h> +#include <linux/kernel.h> +#include <linux/notifier.h> +#include <linux/platform_device.h> +#include <linux/slab.h> +#include <linux/input/matrix_keypad.h> +#include <linux/mfd/cros_ec.h> +#include <linux/mfd/cros_ec_commands.h> + +/* + * @rows: Number of rows in the keypad + * @cols: Number of columns in the keypad + * @row_shift: log2 or number of rows, rounded up + * @keymap_data: Matrix keymap data used to convert to keyscan values + * @ghost_filter: true to enable the matrix key-ghosting filter + * @dev: Device pointer + * @idev: Input device + * @ec: Top level ChromeOS device to use to talk to EC + * @event_notifier: interrupt event notifier for transport devices + */ +struct cros_ec_keyb { + unsigned int rows; + unsigned int cols; + int row_shift; + const struct matrix_keymap_data *keymap_data; + bool ghost_filter; + + struct device *dev; + struct input_dev *idev; + struct cros_ec_device *ec; + struct notifier_block notifier; +}; + + +static bool cros_ec_keyb_row_has_ghosting(struct cros_ec_keyb *ckdev, + uint8_t *buf, int row) +{ + int pressed_in_row = 0; + int row_has_teeth = 0; + int col, mask; + + mask = 1 << row; + for (col = 0; col < ckdev->cols; col++) { + if (buf[col] & mask) { + pressed_in_row++; + row_has_teeth |= buf[col] & ~mask; + if (pressed_in_row > 1 && row_has_teeth) { + /* ghosting */ + dev_dbg(ckdev->dev, + "ghost found at: r%d c%d, pressed %d, teeth 0x%x\n", + row, col, pressed_in_row, + row_has_teeth); + return true; + } + } + } + + return false; +} + +/* + * Returns true when there is at least one combination of pressed keys that + * results in ghosting. + */ +static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf) +{ + int row; + + /* + * Ghosting happens if for any pressed key X there are other keys + * pressed both in the same row and column of X as, for instance, + * in the following diagram: + * + * . . Y . g . + * . . . . . . + * . . . . . . + * . . X . Z . + * + * In this case only X, Y, and Z are pressed, but g appears to be + * pressed too (see Wikipedia). + * + * We can detect ghosting in a single pass (*) over the keyboard state + * by maintaining two arrays. pressed_in_row counts how many pressed + * keys we have found in a row. row_has_teeth is true if any of the + * pressed keys for this row has other pressed keys in its column. If + * at any point of the scan we find that a row has multiple pressed + * keys, and at least one of them is at the intersection with a column + * with multiple pressed keys, we're sure there is ghosting. + * Conversely, if there is ghosting, we will detect such situation for + * at least one key during the pass. + * + * (*) This looks linear in the number of keys, but it's not. We can + * cheat because the number of rows is small. + */ + for (row = 0; row < ckdev->rows; row++) + if (cros_ec_keyb_row_has_ghosting(ckdev, buf, row)) + return true; + + return false; +} + +/* + * Compares the new keyboard state to the old one and produces key + * press/release events accordingly. The keyboard state is 13 bytes (one byte + * per column) + */ +static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev, + uint8_t *kb_state, int len) +{ + struct input_dev *idev = ckdev->idev; + int col, row; + int new_state; + int num_cols; + + num_cols = len; + + if (ckdev->ghost_filter && cros_ec_keyb_has_ghosting(ckdev, kb_state)) { + /* + * Simple-minded solution: ignore this state. The obvious + * improvement is to only ignore changes to keys involved in + * the ghosting, but process the other changes. + */ + dev_dbg(ckdev->dev, "ghosting found\n"); + return; + } + + for (col = 0; col < ckdev->cols; col++) { + for (row = 0; row < ckdev->rows; row++) { + int pos = MATRIX_SCAN_CODE(row, col, ckdev->row_shift); + const unsigned short *keycodes = idev->keycode; + int code; + + code = keycodes[pos]; + new_state = kb_state[col] & (1 << row); + if (!!new_state != test_bit(code, idev->key)) { + dev_dbg(ckdev->dev, + "changed: [r%d c%d]: byte %02x\n", + row, col, new_state); + + input_report_key(idev, code, new_state); + } + } + } + input_sync(ckdev->idev); +} + +static int cros_ec_keyb_open(struct input_dev *dev) +{ + struct cros_ec_keyb *ckdev = input_get_drvdata(dev); + + return blocking_notifier_chain_register(&ckdev->ec->event_notifier, + &ckdev->notifier); +} + +static void cros_ec_keyb_close(struct input_dev *dev) +{ + struct cros_ec_keyb *ckdev = input_get_drvdata(dev); + + blocking_notifier_chain_unregister(&ckdev->ec->event_notifier, + &ckdev->notifier); +} + +static int cros_ec_keyb_get_state(struct cros_ec_keyb *ckdev, uint8_t *kb_state) +{ + return ckdev->ec->command_recv(ckdev->ec, EC_CMD_MKBP_STATE, + kb_state, ckdev->cols); +} + +static int cros_ec_keyb_work(struct notifier_block *nb, + unsigned long state, void *_notify) +{ + int ret; + struct cros_ec_keyb *ckdev = container_of(nb, struct cros_ec_keyb, + notifier); + uint8_t kb_state[ckdev->cols]; + + ret = cros_ec_keyb_get_state(ckdev, kb_state); + if (ret >= 0) + cros_ec_keyb_process(ckdev, kb_state, ret); + + return NOTIFY_DONE; +} + +/* Clear any keys in the buffer */ +static void cros_ec_keyb_clear_keyboard(struct cros_ec_keyb *ckdev) +{ + uint8_t old_state[ckdev->cols]; + uint8_t new_state[ckdev->cols]; + unsigned long duration; + int i, ret; + + /* + * Keep reading until we see that the scan state does not change. + * That indicates that we are done. + * + * Assume that the EC keyscan buffer is at most 32 deep. + */ + duration = jiffies; + ret = cros_ec_keyb_get_state(ckdev, new_state); + for (i = 1; !ret && i < 32; i++) { + memcpy(old_state, new_state, sizeof(old_state)); + ret = cros_ec_keyb_get_state(ckdev, new_state); + if (0 == memcmp(old_state, new_state, sizeof(old_state))) + break; + } + duration = jiffies - duration; + dev_info(ckdev->dev, "Discarded %d keyscan(s) in %dus\n", i, + jiffies_to_usecs(duration)); +} + +static int cros_ec_keyb_probe(struct platform_device *pdev) +{ + struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent); + struct device *dev = ec->dev; + struct cros_ec_keyb *ckdev; + struct input_dev *idev; + struct device_node *np; + int err; + + np = pdev->dev.of_node; + if (!np) + return -ENODEV; + + ckdev = devm_kzalloc(&pdev->dev, sizeof(*ckdev), GFP_KERNEL); + if (!ckdev) + return -ENOMEM; + err = matrix_keypad_parse_of_params(&pdev->dev, &ckdev->rows, + &ckdev->cols); + if (err) + return err; + + idev = devm_input_allocate_device(&pdev->dev); + if (!idev) + return -ENOMEM; + + ckdev->ec = ec; + ckdev->notifier.notifier_call = cros_ec_keyb_work; + ckdev->dev = dev; + dev_set_drvdata(&pdev->dev, ckdev); + + idev->name = ec->ec_name; + idev->phys = ec->phys_name; + __set_bit(EV_REP, idev->evbit); + + idev->id.bustype = BUS_VIRTUAL; + idev->id.version = 1; + idev->id.product = 0; + idev->dev.parent = &pdev->dev; + idev->open = cros_ec_keyb_open; + idev->close = cros_ec_keyb_close; + + ckdev->ghost_filter = of_property_read_bool(np, + "google,needs-ghost-filter"); + + err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols, + NULL, idev); + if (err) { + dev_err(dev, "cannot build key matrix\n"); + return err; + } + + ckdev->row_shift = get_count_order(ckdev->cols); + + input_set_capability(idev, EV_MSC, MSC_SCAN); + input_set_drvdata(idev, ckdev); + ckdev->idev = idev; + err = input_register_device(ckdev->idev); + if (err) { + dev_err(dev, "cannot register input device\n"); + return err; + } + + return 0; +} + +#ifdef CONFIG_PM_SLEEP +static int cros_ec_keyb_resume(struct device *dev) +{ + struct cros_ec_keyb *ckdev = dev_get_drvdata(dev); + + /* + * When the EC is not a wake source, then it could not have caused the + * resume, so we clear the EC's key scan buffer. If the EC was a + * wake source (e.g. the lid is open and the user might press a key to + * wake) then the key scan buffer should be preserved. + */ + if (ckdev->ec->was_wake_device) + cros_ec_keyb_clear_keyboard(ckdev); + + return 0; +} + +#endif + +static SIMPLE_DEV_PM_OPS(cros_ec_keyb_pm_ops, NULL, cros_ec_keyb_resume); + +static struct platform_driver cros_ec_keyb_driver = { + .probe = cros_ec_keyb_probe, + .driver = { + .name = "cros-ec-keyb", + .pm = &cros_ec_keyb_pm_ops, + }, +}; + +module_platform_driver(cros_ec_keyb_driver); + +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("ChromeOS EC keyboard driver"); +MODULE_ALIAS("platform:cros-ec-keyb"); |