Re: [PATCH v2 RESEND] HID: appletb-kbd: add option to switch default layer on double pressing fn key

[Aditya Garg]

Hi Jiri

Can I have an update on this?

On Saturday, 20 June 2026 at 4:56 PM, Aditya Garg <gargaditya08@xxxxxxxxx> wrote:

> From: Aditya Garg <gargaditya08@xxxxxxxxx>
> 
> This patch enables a user to switch the default layer from media to fn
> keys and vice-versa upon double pressing the fn key. This behaviour can
> be configured using the double_press_switch_time module parameter whose
> value depicts the time in milliseconds within which the fn key must be
> pressed again to switch the default layer. If set to 0, it simply
> disables this behaviour.
> 
> Signed-off-by: Aditya Garg <gargaditya08@xxxxxxxxx>
> ---
> 
> v2: added a check to ensure negative fn switch times are ignored.
> 
>  drivers/hid/hid-appletb-kbd.c | 60 +++++++++++++++++++++++++++++++----
>  1 file changed, 53 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/hid/hid-appletb-kbd.c b/drivers/hid/hid-appletb-kbd.c
> index 462010a75899..34bfc595949d 100644
> --- a/drivers/hid/hid-appletb-kbd.c
> +++ b/drivers/hid/hid-appletb-kbd.c
> @@ -56,6 +56,12 @@ static int appletb_tb_idle_timeout = 15;
>  module_param_named(idle_timeout, appletb_tb_idle_timeout, int, 0644);
>  MODULE_PARM_DESC(idle_timeout, "Idle timeout in sec");
>  
> +static int appletb_tb_double_press_switch_layers;
> +module_param_named(double_press_switch_time,
> +		   appletb_tb_double_press_switch_layers, int, 0644);
> +MODULE_PARM_DESC(double_press_switch_time, "Time in ms within which if fn key is double "
> +					   "pressed will switch layers");
> +
>  struct appletb_kbd {
>  	struct hid_field *mode_field;
>  	struct input_handler inp_handler;
> @@ -68,6 +74,7 @@ struct appletb_kbd {
>  	bool has_turned_off;
>  	u8 saved_mode;
>  	u8 current_mode;
> +	unsigned long last_fn_press;
>  };
>  
>  static const struct key_entry appletb_kbd_keymap[] = {
> @@ -243,6 +250,18 @@ static int appletb_kbd_hid_event(struct hid_device *hdev, struct hid_field *fiel
>  	return kbd->current_mode == APPLETB_KBD_MODE_OFF;
>  }
>  
> +static u8 appletb_switch_mode(u8 mode)
> +{
> +	switch (mode) {
> +	case APPLETB_KBD_MODE_SPCL:
> +		return APPLETB_KBD_MODE_FN;
> +	case APPLETB_KBD_MODE_FN:
> +		return APPLETB_KBD_MODE_SPCL;
> +	default:
> +		return mode;
> +	}
> +}
> +
>  static void appletb_kbd_inp_event(struct input_handle *handle, unsigned int type,
>  			      unsigned int code, int value)
>  {
> @@ -250,15 +269,42 @@ static void appletb_kbd_inp_event(struct input_handle *handle, unsigned int type
>  
>  	reset_inactivity_timer(kbd);
>  
> -	if (type == EV_KEY && code == KEY_FN && appletb_tb_fn_toggle &&
> -		(kbd->current_mode == APPLETB_KBD_MODE_SPCL ||
> -		 kbd->current_mode == APPLETB_KBD_MODE_FN)) {
> +	if (type == EV_KEY && code == KEY_FN &&
> +	    (kbd->current_mode == APPLETB_KBD_MODE_SPCL ||
> +	     kbd->current_mode == APPLETB_KBD_MODE_FN)) {
> +
>  		if (value == 1) {
> -			kbd->saved_mode = kbd->current_mode;
> -			appletb_kbd_set_mode(kbd, kbd->current_mode == APPLETB_KBD_MODE_SPCL
> -						? APPLETB_KBD_MODE_FN : APPLETB_KBD_MODE_SPCL);
> +			if (appletb_tb_double_press_switch_layers > 0) {
> +				unsigned long now = jiffies;
> +
> +				if (time_before(now, kbd->last_fn_press +
> +					msecs_to_jiffies(appletb_tb_double_press_switch_layers))) {
> +
> +					appletb_tb_def_mode =
> +						appletb_switch_mode(
> +							appletb_tb_def_mode);
> +
> +					appletb_kbd_set_mode(kbd,
> +						appletb_tb_def_mode);
> +
> +					kbd->saved_mode = appletb_tb_def_mode;
> +					kbd->last_fn_press = 0;
> +
> +					return;
> +				}
> +
> +				kbd->last_fn_press = now;
> +			}
> +			if (appletb_tb_fn_toggle) {
> +				kbd->saved_mode = kbd->current_mode;
> +
> +				appletb_kbd_set_mode(kbd,
> +					appletb_switch_mode(kbd->current_mode));
> +			}
> +
>  		} else if (value == 0) {
> -			if (kbd->saved_mode != kbd->current_mode)
> +			if (appletb_tb_fn_toggle &&
> +			    kbd->saved_mode != kbd->current_mode)
>  				appletb_kbd_set_mode(kbd, kbd->saved_mode);
>  		}
>  	}
> 
> Range-diff against v1:
> 1:  5c9d8c8ba8c0 ! 1:  4f6a818b98b9 HID: appletb-kbd: add option to switch default layer on double pressing fn key
>     @@ drivers/hid/hid-appletb-kbd.c: static void appletb_kbd_inp_event(struct input_ha
>      -			kbd->saved_mode = kbd->current_mode;
>      -			appletb_kbd_set_mode(kbd, kbd->current_mode == APPLETB_KBD_MODE_SPCL
>      -						? APPLETB_KBD_MODE_FN : APPLETB_KBD_MODE_SPCL);
>     -+			if (appletb_tb_double_press_switch_layers) {
>     ++			if (appletb_tb_double_press_switch_layers > 0) {
>      +				unsigned long now = jiffies;
>      +
>      +				if (time_before(now, kbd->last_fn_press +
> -- 
> 2.53.0
> 
>