cros_ec_keyb.c

/*
 * 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/bitops.h>
#include <linux/i2c.h>
#include <linux/input.h>
#include <linux/interrupt.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
 * @valid_keys: bitmap of existing keys for each matrix column
 * @old_kb_state: bitmap of keys pressed last scan
 * @dev: Device pointer
 * @idev: Input device
 * @ec: Top level ChromeOS device to use to talk to EC
 * @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;
	uint8_t *valid_keys;
	uint8_t *old_kb_state;

	struct device *dev;
	struct input_dev *idev;
	struct cros_ec_device *ec;
	struct notifier_block notifier;
};


/*
 * 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 col1, col2, buf1, buf2;
	struct device *dev = ckdev->dev;
	uint8_t *valid_keys = ckdev->valid_keys;

	/*
	 * 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).
	 */
	for (col1 = 0; col1 < ckdev->cols; col1++) {
		buf1 = buf[col1] & valid_keys[col1];
		for (col2 = col1 + 1; col2 < ckdev->cols; col2++) {
			buf2 = buf[col2] & valid_keys[col2];
			if (hweight8(buf1 & buf2) > 1) {
				dev_dbg(dev, "ghost found at: B[%02d]:0x%02x & B[%02d]:0x%02x",
					col1, buf1, col2, buf2);
				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 old_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;

			new_state = kb_state[col] & (1 << row);
			old_state = ckdev->old_kb_state[col] & (1 << row);
			if (new_state != old_state) {
				dev_dbg(ckdev->dev,
					"changed: [r%d c%d]: byte %02x\n",
					row, col, new_state);

				input_report_key(idev, keycodes[pos],
						 new_state);
			}
		}
		ckdev->old_kb_state[col] = kb_state[col];
	}
	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_work(struct notifier_block *nb,
			     unsigned long queued_during_suspend, void *_notify)
{
	struct cros_ec_keyb *ckdev = container_of(nb, struct cros_ec_keyb,
						  notifier);

	if (ckdev->ec->event_data.event_type != EC_MKBP_EVENT_KEY_MATRIX)
		return NOTIFY_DONE;
	/*
	 * If EC is not the wake source, discard key state changes during
	 * suspend.
	 */
	if (queued_during_suspend)
		return NOTIFY_OK;
	if (ckdev->ec->event_size != ckdev->cols) {
		dev_err(ckdev->dev,
			"Discarded incomplete key matrix event.\n");
		return NOTIFY_OK;
	}
	cros_ec_keyb_process(ckdev, ckdev->ec->event_data.data.key_matrix,
			     ckdev->ec->event_size);
	return NOTIFY_OK;
}

/*
 * Walks keycodes flipping bit in buffer COLUMNS deep where bit is ROW.  Used by
 * ghosting logic to ignore NULL or virtual keys.
 */
static void cros_ec_keyb_compute_valid_keys(struct cros_ec_keyb *ckdev)
{
	int row, col;
	int row_shift = ckdev->row_shift;
	unsigned short *keymap = ckdev->idev->keycode;
	unsigned short code;

	BUG_ON(ckdev->idev->keycodesize != sizeof(*keymap));

	for (col = 0; col < ckdev->cols; col++) {
		for (row = 0; row < ckdev->rows; row++) {
			code = keymap[MATRIX_SCAN_CODE(row, col, row_shift)];
			if (code && (code != KEY_BATTERY))
				ckdev->valid_keys[col] |= 1 << row;
		}
		dev_dbg(ckdev->dev, "valid_keys[%02d] = 0x%02x\n",
			col, ckdev->valid_keys[col]);
	}
}

static int cros_ec_keyb_probe(struct platform_device *pdev)
{
	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
	struct device *dev = &pdev->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(dev, sizeof(*ckdev), GFP_KERNEL);
	if (!ckdev)
		return -ENOMEM;
	err = matrix_keypad_parse_of_params(dev, &ckdev->rows, &ckdev->cols);
	if (err)
		return err;

	ckdev->valid_keys = devm_kzalloc(dev, ckdev->cols, GFP_KERNEL);
	if (!ckdev->valid_keys)
		return -ENOMEM;

	ckdev->old_kb_state = devm_kzalloc(dev, ckdev->cols, GFP_KERNEL);
	if (!ckdev->old_kb_state)
		return -ENOMEM;

	idev = devm_input_allocate_device(dev);
	if (!idev)
		return -ENOMEM;

	ckdev->ec = ec;
	ckdev->notifier.notifier_call = cros_ec_keyb_work;
	ckdev->dev = dev;
	dev_set_drvdata(dev, ckdev);

	idev->name = CROS_EC_DEV_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 = 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;
	cros_ec_keyb_compute_valid_keys(ckdev);

	err = input_register_device(ckdev->idev);
	if (err) {
		dev_err(dev, "cannot register input device\n");
		return err;
	}

	return 0;
}

#ifdef CONFIG_OF
static const struct of_device_id cros_ec_keyb_of_match[] = {
	{ .compatible = "google,cros-ec-keyb" },
	{},
};
MODULE_DEVICE_TABLE(of, cros_ec_keyb_of_match);
#endif

static struct platform_driver cros_ec_keyb_driver = {
	.probe = cros_ec_keyb_probe,
	.driver = {
		.name = "cros-ec-keyb",
		.of_match_table = of_match_ptr(cros_ec_keyb_of_match),
	},
};

module_platform_driver(cros_ec_keyb_driver);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("ChromeOS EC keyboard driver");
MODULE_ALIAS("platform:cros-ec-keyb");