input: Add ChromeOS EC keyboard driver

ChromeOS EC Keyboard

Google's ChromeOS EC Keyboard is a simple matrix keyboard implemented on

a separate EC (Embedded Controller) device. It provides a message for reading

key scans from the EC. These are then converted into keycodes for processing

by the kernel.

This binding is based on matrix-keymap.txt and extends/modifies it as follows:

Required properties:

- compatible: "google,cros-ec-keyb"

Optional properties:

- google,needs-ghost-filter: True to enable a ghost filter for the matrix

keyboard. This is recommended if the EC does not have its own logic or

hardware for this.

Example:

cros-ec-keyb {

	compatible = "google,cros-ec-keyb";

	keypad,num-rows = <8>;

	keypad,num-columns = <13>;

	google,needs-ghost-filter;

	/*

	 * Keymap entries take the form of 0xRRCCKKKK where

	 * RR=Row CC=Column KKKK=Key Code

	 * The values below are for a US keyboard layout and

	 * are taken from the Linux driver. Note that the

	 * 102ND key is not used for US keyboards.

	 */

	linux,keymap = <

		/* CAPSLCK F1         B          F10     */

		0x0001003a 0x0002003b 0x00030030 0x00040044

		/* N       =          R_ALT      ESC     */

		0x00060031 0x0008000d 0x000a0064 0x01010001

		/* F4      G          F7         H       */

		0x0102003e 0x01030022 0x01040041 0x01060023

		/* '       F9         BKSPACE    L_CTRL  */

		0x01080028 0x01090043 0x010b000e 0x0200001d

		/* TAB     F3         T          F6      */

		0x0201000f 0x0202003d 0x02030014 0x02040040

		/* ]       Y          102ND      [       */

		0x0205001b 0x02060015 0x02070056 0x0208001a

		/* F8      GRAVE      F2         5       */

		0x02090042 0x03010029 0x0302003c 0x03030006

		/* F5      6          -          \       */

		0x0304003f 0x03060007 0x0308000c 0x030b002b

		/* R_CTRL  A          D          F       */

		0x04000061 0x0401001e 0x04020020 0x04030021

		/* S       K          J          ;       */

		0x0404001f 0x04050025 0x04060024 0x04080027

		/* L       ENTER      Z          C       */

		0x04090026 0x040b001c 0x0501002c 0x0502002e

		/* V       X          ,          M       */

		0x0503002f 0x0504002d 0x05050033 0x05060032

		/* L_SHIFT /          .          SPACE   */

		0x0507002a 0x05080035 0x05090034 0x050B0039

		/* 1       3          4          2       */

		0x06010002 0x06020004 0x06030005 0x06040003

		/* 8       7          0          9       */

		0x06050009 0x06060008 0x0608000b 0x0609000a

		/* L_ALT   DOWN       RIGHT      Q       */

		0x060a0038 0x060b006c 0x060c006a 0x07010010

		/* E       R          W          I       */

		0x07020012 0x07030013 0x07040011 0x07050017

		/* U       R_SHIFT    P          O       */

		0x07060016 0x07070036 0x07080019 0x07090018

		/* UP      LEFT    */

		0x070b0067 0x070c0069>;

};

	  To compile this driver as a module, choose M here: the

	  module will be called w90p910_keypad.

config KEYBOARD_CROS_EC

	tristate "ChromeOS EC keyboard"

	select INPUT_MATRIXKMAP

	depends on MFD_CROS_EC

	help

	  Say Y here to enable the matrix keyboard used by ChromeOS devices

	  and implemented on the ChromeOS EC. You must enable one bus option

	  (MFD_CROS_EC_I2C or MFD_CROS_EC_SPI) to use this.

	  To compile this driver as a module, choose M here: the

	  module will be called cros_ec_keyb.

endif

obj-$(CONFIG_KEYBOARD_ATARI)		+= atakbd.o

obj-$(CONFIG_KEYBOARD_ATKBD)		+= atkbd.o

obj-$(CONFIG_KEYBOARD_BFIN)		+= bf54x-keys.o

obj-$(CONFIG_KEYBOARD_CROS_EC)		+= cros_ec_keyb.o

obj-$(CONFIG_KEYBOARD_DAVINCI)		+= davinci_keyscan.o

obj-$(CONFIG_KEYBOARD_EP93XX)		+= ep93xx_keypad.o

obj-$(CONFIG_KEYBOARD_GOLDFISH_EVENTS)	+= goldfish_events.o

/*

 * 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");