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Message-ID: <20251224152238.485415-2-fabiobaltieri@chromium.org>
Date: Wed, 24 Dec 2025 15:22:37 +0000
From: Fabio Baltieri <fabiobaltieri@...omium.org>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Benson Leung <bleung@...omium.org>,
	Guenter Roeck <groeck@...omium.org>
Cc: Fabio Baltieri <fabiobaltieri@...omium.org>,
	Tzung-Bi Shih <tzungbi@...nel.org>,
	Simon Glass <sjg@...omium.org>,
	linux-input@...r.kernel.org,
	devicetree@...r.kernel.org,
	chrome-platform@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/2] Input: cros_ec_keyb - add function key support

Add support for handling an Fn button and sending separate keycodes for
a subset of keys in the matrix defined in the upper half of the keymap.

Signed-off-by: Fabio Baltieri <fabiobaltieri@...omium.org>
---
 drivers/input/keyboard/cros_ec_keyb.c | 120 ++++++++++++++++++++++----
 1 file changed, 104 insertions(+), 16 deletions(-)

diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c
index 1c6b0461dc35..8b95b4f8a37d 100644
--- a/drivers/input/keyboard/cros_ec_keyb.c
+++ b/drivers/input/keyboard/cros_ec_keyb.c
@@ -29,6 +29,11 @@
 
 #include <linux/unaligned.h>
 
+/* Maximum size of the normal key matrix, this is limited by the host command
+ * key_matrix field defined in ec_response_get_next_data_v3
+ */
+#define CROS_EC_KEYBOARD_COLS_MAX 18
+
 /**
  * struct cros_ec_keyb - Structure representing EC keyboard device
  *
@@ -44,6 +49,11 @@
  * @bs_idev: The input device for non-matrix buttons and switches (or NULL).
  * @notifier: interrupt event notifier for transport devices
  * @vdata: vivaldi function row data
+ * @use_fn_overlay: whether the driver use an fn function overlay
+ * @normal_key_status: active normal keys map
+ * @fn_key_status: active function keys map
+ * @fn_key_pressed: tracks the function key status
+ * @fn_key_triggered: tracks where any function key fired
  */
 struct cros_ec_keyb {
 	unsigned int rows;
@@ -61,6 +71,12 @@ struct cros_ec_keyb {
 	struct notifier_block notifier;
 
 	struct vivaldi_data vdata;
+
+	bool use_fn_overlay;
+	u8 normal_key_status[CROS_EC_KEYBOARD_COLS_MAX];
+	u8 fn_key_status[CROS_EC_KEYBOARD_COLS_MAX];
+	bool fn_key_pressed;
+	bool fn_key_triggered;
 };
 
 /**
@@ -166,16 +182,83 @@ static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf)
 	return false;
 }
 
+static void cros_ec_keyb_process_fn_key(struct cros_ec_keyb *ckdev,
+					int row, int col, bool state)
+{
+	struct input_dev *idev = ckdev->idev;
+	int pos = MATRIX_SCAN_CODE(row, col, ckdev->row_shift);
+
+	ckdev->fn_key_pressed = state;
+
+	if (state) {
+		ckdev->fn_key_triggered = false;
+	} else if (!ckdev->fn_key_triggered) {
+		/*
+		 * Send the original code if nothing else has been pressed
+		 * together with Fn.
+		 */
+		input_event(idev, EV_MSC, MSC_SCAN, pos);
+		input_report_key(idev, KEY_FN, true);
+		input_sync(idev);
+
+		input_event(idev, EV_MSC, MSC_SCAN, pos);
+		input_report_key(idev, KEY_FN, false);
+	}
+}
+
+static void cros_ec_keyb_process_one(struct cros_ec_keyb *ckdev,
+				     int row, int col, bool state)
+{
+	struct input_dev *idev = ckdev->idev;
+	const unsigned short *keycodes = idev->keycode;
+	int pos = MATRIX_SCAN_CODE(row, col, ckdev->row_shift);
+	unsigned int code = keycodes[pos];
+
+	dev_dbg(ckdev->dev, "changed: [r%d c%d]: byte %02x\n", row, col, state);
+
+	if (ckdev->use_fn_overlay) {
+		if (code == KEY_FN)
+			return cros_ec_keyb_process_fn_key(ckdev, row, col, state);
+
+		if (!state) {
+			if (ckdev->fn_key_status[col] & BIT(row)) {
+				pos = MATRIX_SCAN_CODE(row + ckdev->rows, col, ckdev->row_shift);
+				code = keycodes[pos];
+
+				ckdev->fn_key_status[col] &= ~BIT(row);
+			} else if (ckdev->normal_key_status[col] & BIT(row)) {
+				ckdev->normal_key_status[col] &= ~BIT(row);
+			} else {
+				/* Discard, key press code was not sent */
+				return;
+			}
+		} else if (ckdev->fn_key_pressed) {
+			pos = MATRIX_SCAN_CODE(row + ckdev->rows, col, ckdev->row_shift);
+			code = keycodes[pos];
+
+			ckdev->fn_key_triggered = true;
+
+			if (!code)
+				return;
+
+			ckdev->fn_key_status[col] |= BIT(row);
+		} else {
+			ckdev->normal_key_status[col] |= BIT(row);
+		}
+	}
+
+	input_event(idev, EV_MSC, MSC_SCAN, pos);
+	input_report_key(idev, code, state);
+}
 
 /*
  * 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)
+ * press/release events accordingly.  The keyboard state is 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;
@@ -192,20 +275,13 @@ static void cros_ec_keyb_process(struct cros_ec_keyb *ckdev,
 
 	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_event(idev, EV_MSC, MSC_SCAN, pos);
-				input_report_key(idev, keycodes[pos],
-						 new_state);
-			}
+
+			if (new_state == old_state)
+				continue;
+
+			cros_ec_keyb_process_one(ckdev, row, col, new_state);
 		}
 		ckdev->old_kb_state[col] = kb_state[col];
 	}
@@ -597,12 +673,19 @@ static int cros_ec_keyb_register_matrix(struct cros_ec_keyb *ckdev)
 	struct device *dev = ckdev->dev;
 	struct input_dev *idev;
 	const char *phys;
+	unsigned int rows_keymap;
 	int err;
 
 	err = matrix_keypad_parse_properties(dev, &ckdev->rows, &ckdev->cols);
 	if (err)
 		return err;
 
+	if (ckdev->cols > CROS_EC_KEYBOARD_COLS_MAX) {
+		dev_err(dev, "keypad,num-columns too large: %d (max: %d)\n",
+			ckdev->cols, CROS_EC_KEYBOARD_COLS_MAX);
+		return -EINVAL;
+	}
+
 	ckdev->valid_keys = devm_kzalloc(dev, ckdev->cols, GFP_KERNEL);
 	if (!ckdev->valid_keys)
 		return -ENOMEM;
@@ -635,7 +718,12 @@ static int cros_ec_keyb_register_matrix(struct cros_ec_keyb *ckdev)
 	ckdev->ghost_filter = device_property_read_bool(dev,
 					"google,needs-ghost-filter");
 
-	err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows, ckdev->cols,
+	ckdev->use_fn_overlay = device_property_read_bool(dev,
+					"google,use-fn-overlay");
+
+	rows_keymap = ckdev->use_fn_overlay ? ckdev->rows * 2 : ckdev->rows;
+
+	err = matrix_keypad_build_keymap(NULL, NULL, rows_keymap, ckdev->cols,
 					 NULL, idev);
 	if (err) {
 		dev_err(dev, "cannot build key matrix\n");
-- 
2.52.0.351.gbe84eed79e-goog


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