[PATCH v4 0/1] Input: cros_ec_keyb: add function key support

[PATCH v4 0/1] Input: cros_ec_keyb: add function key support

[Fabio Baltieri]

Hi, v4 of the cros-ec-keyb fn key support, reworked the logic to detect
the fn layer automatically, removed the dedicated dt property.

Changes from v3:
  - implemented fn layer runtime detection
  - tweaked cros_ec_keyb_fn_code to return back the correct position
    code

Changes from v2:
  - renamed the dt property to use-fn-map, dropped the example
  - added few function comments
  - added a helper for obtaining the fn code
  - reordered, dt patch first

Changes from v1:
  - change struct to short types
  - refactored the fn key handling in its own function
  - changed props to use the google, prefix
  - reworked the properties to use an overlay map rather than a
    dedicated one


Fabio Baltieri (1):
  Input: cros_ec_keyb - add function key support

 drivers/input/keyboard/cros_ec_keyb.c | 174 +++++++++++++++++++++++---
 1 file changed, 158 insertions(+), 16 deletions(-)

-- 
2.52.0.351.gbe84eed79e-goog

[PATCH v4 1/1] Input: cros_ec_keyb - add function key support

[Fabio Baltieri]

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@chromium.org>
---
 drivers/input/keyboard/cros_ec_keyb.c | 174 +++++++++++++++++++++++---
 1 file changed, 158 insertions(+), 16 deletions(-)

diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c
index 1c6b0461dc35..74ac1700b104 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
+ * @has_fn_map: whether the driver use an fn function map layer
+ * @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 has_fn_map;
+	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 +182,104 @@ static bool cros_ec_keyb_has_ghosting(struct cros_ec_keyb *ckdev, uint8_t *buf)
 	return false;
 }
 
+/*
+ * Process a function key state change, send an event report if appropriate.
+ */
+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);
+	}
+}
+
+/*
+ * Return the Fn code for a normal key row, col combination, optionally set a
+ * position code too.
+ */
+static unsigned int cros_ec_keyb_fn_code(struct cros_ec_keyb *ckdev,
+					 int row, int col, int *pos)
+{
+	struct input_dev *idev = ckdev->idev;
+	const unsigned short *keycodes = idev->keycode;
+	int fn_pos = MATRIX_SCAN_CODE(row + ckdev->rows, col, ckdev->row_shift);
+
+	if (pos)
+		*pos = fn_pos;
+
+	return keycodes[fn_pos];
+}
+
+/*
+ * Process the new state for a single key.
+ */
+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->has_fn_map) {
+		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)) {
+				code = cros_ec_keyb_fn_code(ckdev, row, col, &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) {
+			code = cros_ec_keyb_fn_code(ckdev, row, col, &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 +296,13 @@ 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];
 	}
@@ -582,6 +679,43 @@ static void cros_ec_keyb_parse_vivaldi_physmap(struct cros_ec_keyb *ckdev)
 	ckdev->vdata.num_function_row_keys = n_physmap;
 }
 
+/* Returns true if there is a KEY_FN code defined in the normal keymap */
+static bool cros_ec_keyb_has_fn_key(struct cros_ec_keyb *ckdev)
+{
+	struct input_dev *idev = ckdev->idev;
+	const unsigned short *keycodes = idev->keycode;
+
+	for (int row = 0; row < ckdev->rows; row++) {
+		for (int col = 0; col < ckdev->cols; col++) {
+			int pos = MATRIX_SCAN_CODE(row, col, ckdev->row_shift);
+
+			if (keycodes[pos] == KEY_FN)
+				return true;
+		}
+	}
+
+	return false;
+}
+
+/*
+ * Returns true if there is a KEY_FN defined and at least one key in the fn
+ * layer keymap
+ */
+static bool cros_ec_keyb_has_fn_map(struct cros_ec_keyb *ckdev)
+{
+	if (!cros_ec_keyb_has_fn_key(ckdev))
+		return false;
+
+	for (int row = 0; row < ckdev->rows; row++) {
+		for (int col = 0; col < ckdev->cols; col++) {
+			if (cros_ec_keyb_fn_code(ckdev, row, col, NULL) != 0)
+				return true;
+		}
+	}
+
+	return false;
+}
+
 /**
  * cros_ec_keyb_register_matrix - Register matrix keys
  *
@@ -603,6 +737,12 @@ static int cros_ec_keyb_register_matrix(struct cros_ec_keyb *ckdev)
 	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 +775,7 @@ 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,
+	err = matrix_keypad_build_keymap(NULL, NULL, ckdev->rows * 2, ckdev->cols,
 					 NULL, idev);
 	if (err) {
 		dev_err(dev, "cannot build key matrix\n");
@@ -650,6 +790,8 @@ static int cros_ec_keyb_register_matrix(struct cros_ec_keyb *ckdev)
 	cros_ec_keyb_compute_valid_keys(ckdev);
 	cros_ec_keyb_parse_vivaldi_physmap(ckdev);
 
+	ckdev->has_fn_map = cros_ec_keyb_has_fn_map(ckdev);
+
 	err = input_register_device(ckdev->idev);
 	if (err) {
 		dev_err(dev, "cannot register input device\n");
-- 
2.52.0.351.gbe84eed79e-goog

Re: [PATCH v4 1/1] Input: cros_ec_keyb - add function key support

[Simon Glass]

Hi Fabio,

On Tue, 6 Jan 2026 at 04:29, Fabio Baltieri <fabiobaltieri@chromium.org> wrote:
>
> 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@chromium.org>
> ---
>  drivers/input/keyboard/cros_ec_keyb.c | 174 +++++++++++++++++++++++---
>  1 file changed, 158 insertions(+), 16 deletions(-)
>

Reviewed-by: Simon Glass <sjg@chromium.org>

> diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c
> index 1c6b0461dc35..74ac1700b104 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
> + * @has_fn_map: whether the driver use an fn function map layer

How about: driver uses an fn function-map layer

Regards.

Simon

Re: [PATCH v4 1/1] Input: cros_ec_keyb - add function key support

[Fabio Baltieri]

On Tue, Jan 06, 2026 at 09:22:06AM -0700, Simon Glass wrote:
> Hi Fabio,
> 
> On Tue, 6 Jan 2026 at 04:29, Fabio Baltieri <fabiobaltieri@chromium.org> wrote:
> >
> > 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@chromium.org>
> > ---
> >  drivers/input/keyboard/cros_ec_keyb.c | 174 +++++++++++++++++++++++---
> >  1 file changed, 158 insertions(+), 16 deletions(-)
> >
> 
> Reviewed-by: Simon Glass <sjg@chromium.org>

Thanks again!

> 
> > diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c
> > index 1c6b0461dc35..74ac1700b104 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
> > + * @has_fn_map: whether the driver use an fn function map layer
> 
> How about: driver uses an fn function-map layer

Yeah sounds good, will send a v5 with that comment tweaked.