[PATCH v6 6/6] Input: Add ChromeOS EC keyboard driver

Simon Glass
2013-02-25T22:10:56Z

Use the key-matrix layer to interpret key scan information from the EC
and inject input based on the FDT-supplied key map. This driver registers
itself with the ChromeOS EC driver to perform communications.

The matrix-keypad FDT binding is used with a small addition to control
ghosting.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Luigi Semenzato <semenzato@chromium.org>
Signed-off-by: Vincent Palatin <vpalatin@chromium.org>
---
Changes in v6:
- Fix incorrect indentation in cros_ec_keyb_process()
- Remove unnecessary assignment to NULL in probe function

Changes in v5:
- Fix {} style nit in cros_ec_keyb_has_ghosting
- Correct key lookup logic which was broken in previous version
- Switch cros_ec_keyb driver to use devm

Changes in v4:
- Add 'depends on MFD_CROS_EC' to Kconfig
- Remove use of wake_notifier
- Remove manual code to locate device tree node
- Add resume handler to clear keyboard scan buffer if required

Changes in v3:
- Remove 'select MFD_CROS_EC' from Kconfig as it isn't necessary
- Remove old_state by using input layer's idev->key
- Move inner loop of cros_ec_keyb_has_ghosting() into its own function and simplify
- Add check for not finding the device tree node
- Remove comment about leaking matrix_keypad_build_keymap()
- Use platform_get_drvdata() where possible
- Remove call to input_free_device() after input_unregister_device()

Changes in v2:
- Remove use of __devinit/__devexit
- Use function to read matrix-keypad parameters from DT
- Remove key autorepeat parameters from DT binding and driver
- Use unsigned int for rows/cols

.../devicetree/bindings/input/cros-ec-keyb.txt | 72 +++++
drivers/input/keyboard/Kconfig | 12 +
drivers/input/keyboard/Makefile | 1 +
drivers/input/keyboard/cros_ec_keyb.c | 334 +++++++++++++++++++++
4 files changed, 419 insertions(+)
create mode 100644 Documentation/devicetree/bindings/input/cros-ec-keyb.txt
create mode 100644 drivers/input/keyboard/cros_ec_keyb.c

diff --git a/Documentation/devicetree/bindings/input/cros-ec-keyb.txt b/Documentation/devicetree/bindings/input/cros-ec-keyb.txt
new file mode 100644
index 0000000..0f6355c
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/cros-ec-keyb.txt
@@ -0,0 +1,72 @@
+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>;
+};
diff --git a/drivers/input/keyboard/Kconfig b/drivers/input/keyboard/Kconfig
index 5a240c6..a087d3f 100644
--- a/drivers/input/keyboard/Kconfig
+++ b/drivers/input/keyboard/Kconfig
@@ -618,4 +618,16 @@ config KEYBOARD_W90P910
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
diff --git a/drivers/input/keyboard/Makefile b/drivers/input/keyboard/Makefile
index 44e7600..61b739c 100644
--- a/drivers/input/keyboard/Makefile
+++ b/drivers/input/keyboard/Makefile
@@ -11,6 +11,7 @@ obj-$(CONFIG_KEYBOARD_AMIGA) += amikbd.o
obj-$(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_GPIO) += gpio_keys.o
diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c
new file mode 100644
index 0000000..49557f2
--- /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");
--
1.8.1.3