/*
   * 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/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
   */
  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;
  };
  
  
  /*
   * 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
  ");
  		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
  ",
  					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_get_state(struct cros_ec_keyb *ckdev, uint8_t *kb_state)
  {
  	int ret = 0;
  	struct cros_ec_command *msg;
  
  	msg = kmalloc(sizeof(*msg) + ckdev->cols, GFP_KERNEL);
  	if (!msg)
  		return -ENOMEM;
  
  	msg->version = 0;
  	msg->command = EC_CMD_MKBP_STATE;
  	msg->insize = ckdev->cols;
  	msg->outsize = 0;
  
  	ret = cros_ec_cmd_xfer(ckdev->ec, msg);
  	if (ret < 0) {
  		dev_err(ckdev->dev, "Error transferring EC message %d
  ", ret);
  		goto exit;
  	}
  
  	memcpy(kb_state, msg->data, ckdev->cols);
  exit:
  	kfree(msg);
  	return ret;
  }
  
  static irqreturn_t cros_ec_keyb_irq(int irq, void *data)
  {
  	struct cros_ec_keyb *ckdev = data;
  	struct cros_ec_device *ec = ckdev->ec;
  	int ret;
  	uint8_t kb_state[ckdev->cols];
  
  	if (device_may_wakeup(ec->dev))
  		pm_wakeup_event(ec->dev, 0);
  
  	ret = cros_ec_keyb_get_state(ckdev, kb_state);
  	if (ret >= 0)
  		cros_ec_keyb_process(ckdev, kb_state, ret);
  	else
  		dev_err(ec->dev, "failed to get keyboard state: %d
  ", ret);
  
  	return IRQ_HANDLED;
  }
  
  static int cros_ec_keyb_open(struct input_dev *dev)
  {
  	struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
  	struct cros_ec_device *ec = ckdev->ec;
  
  	return request_threaded_irq(ec->irq, NULL, cros_ec_keyb_irq,
  					IRQF_TRIGGER_LOW | IRQF_ONESHOT,
  					"cros_ec_keyb", ckdev);
  }
  
  static void cros_ec_keyb_close(struct input_dev *dev)
  {
  	struct cros_ec_keyb *ckdev = input_get_drvdata(dev);
  	struct cros_ec_device *ec = ckdev->ec;
  
  	free_irq(ec->irq, ckdev);
  }
  
  /*
   * 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
  ",
  			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 = 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;
  
  	ckdev->valid_keys = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
  	if (!ckdev->valid_keys)
  		return -ENOMEM;
  
  	ckdev->old_kb_state = devm_kzalloc(&pdev->dev, ckdev->cols, GFP_KERNEL);
  	if (!ckdev->old_kb_state)
  		return -ENOMEM;
  
  	idev = devm_input_allocate_device(&pdev->dev);
  	if (!idev)
  		return -ENOMEM;
  
  	if (!ec->irq) {
  		dev_err(dev, "no EC IRQ specified
  ");
  		return -EINVAL;
  	}
  
  	ckdev->ec = ec;
  	ckdev->dev = dev;
  	dev_set_drvdata(&pdev->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 = &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
  ");
  		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
  ");
  		return err;
  	}
  
  	return 0;
  }
  
  #ifdef CONFIG_PM_SLEEP
  /* 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
  ", i,
  		jiffies_to_usecs(duration));
  }
  
  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);
  
  #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),
  		.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");