Re: [PATCH v2 1/3] platform/x86: panasonic-laptop: Handle CF-33 rotation-lock button

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

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On Thu, 13 Aug 2026, Hilgad Montelo wrote:

> On the Panasonic Toughbook CF-33 the bezel "Rotation Lock" button does
> not signal via ACPI notify like the other hotkeys. Instead the
> embedded controller injects raw i8042/PS2 scancodes that alias the
> real Left-GUI/Meta key:
> 
>     press:   e0 5b   65
>     release: e5      e0 db
> 
> e0 5b / e0 db are the standard AT scancode for the physical Left-GUI
> key. The bare 65 / e5 bytes interleaved with them are not valid codes
> for any real key and only ever appear as part of this vendor signal
> (confirmed by tracing raw bytes crossing the i8042 port on the actual
> hardware). Left unfiltered, this shows up as a spurious KEY_LEFTMETA +
> KEY_F14 combo, which does nothing useful and can trigger desktop
> environment Meta-key bindings on every press.
> 
> This driver already installs an i8042 filter (panasonic_i8042_filter)
> to de-duplicate volume key events. Extend it with a small state
> machine that recognizes and swallows the exact e0 5b 65 ... e5 e0 db
> sequence, and emits a single debounced KEY_ROTATE_LOCK_TOGGLE event
> instead. The 600ms debounce is needed because the EC repeats the
> make/break unit every ~280-400ms for as long as the button is
> physically held, which would otherwise fire multiple toggles for one
> tap. If a byte sequence starts the same way but doesn't complete the
> pattern, the buffered e0 5b bytes are replayed unfiltered, so a
> genuine Left-GUI keypress is unaffected.
> 
> Verified on a CF-33 Mk1: each button press now produces exactly one
> KEY_ROTATE_LOCK_TOGGLE pair, the plain keyboard device stays silent
> during presses (no more stray LEFTMETA/F14), and GNOME's auto-rotate
> lock correctly engages/disengages. Brightness and volume hotkeys are
> unaffected.
> 
> Signed-off-by: Hilgad Montelo <hilgad.montelo@gmail.com>
> ---
>  drivers/platform/x86/panasonic-laptop.c | 85 ++++++++++++++++++++++++-
>  1 file changed, 84 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/panasonic-laptop.c b/drivers/platform/x86/panasonic-laptop.c
> index 719add7..0c0e4a6 100644
> --- a/drivers/platform/x86/panasonic-laptop.c
> +++ b/drivers/platform/x86/panasonic-laptop.c
> @@ -127,6 +127,7 @@
>  #include <linux/init.h>
>  #include <linux/input.h>
>  #include <linux/input/sparse-keymap.h>
> +#include <linux/jiffies.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/platform_device.h>
> @@ -256,15 +257,81 @@ struct pcc_acpi {
>  /*
>   * On some Panasonic models the volume up / down / mute keys send duplicate
>   * keypress events over the PS/2 kbd interface, filter these out.
> + *
> + * On the CF-33 the bezel "Rotation Lock" button also signals over this same
> + * interface, instead of via an ACPI notify like the other hotkeys. It does
> + * so by injecting scancodes that alias the real Left-GUI/Meta key
> + * (e0 5b make / e0 db break), interleaved with a bare byte (0x65 / 0xe5)
> + * that no physical key on this keyboard uses. Left unfiltered this shows up
> + * as a bogus LEFTMETA+F14 combo. We recognize and swallow the whole
> + * sequence and emit a single debounced KEY_ROTATE_LOCK_TOGGLE instead; any
> + * byte that breaks the expected pattern is treated as a genuine key and
> + * replayed unfiltered.
>   */
> +enum rot_lock_state {
> +	ROT_IDLE,
> +	ROT_WAIT_65,
> +	ROT_WAIT_E5,
> +	ROT_WAIT_E0B,
> +	ROT_WAIT_DB,
> +};
> +
>  static bool panasonic_i8042_filter(unsigned char data, unsigned char str,
>  				   struct serio *port, void *context)
>  {
> +	struct pcc_acpi *pcc = context;
>  	static bool extended;
> +	static enum rot_lock_state rstate = ROT_IDLE;
> +	static unsigned long last_toggle;
> +	const unsigned long debounce = msecs_to_jiffies(600);

Please try to sort the 4 variables into reverse-xmas tree order (the 
context assignment feels boilerplate noise so it can be left as the 
first entry but that's up to you).

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

>  
>  	if (str & I8042_STR_AUXDATA)
>  		return false;
>  
> +	switch (rstate) {
> +	case ROT_WAIT_65:
> +		if (data == 0x65) {
> +			rstate = ROT_WAIT_E5;
> +			if (pcc && pcc->input_dev &&
> +			    time_after(jiffies, last_toggle + debounce)) {
> +				input_report_key(pcc->input_dev,
> +						  KEY_ROTATE_LOCK_TOGGLE, 1);
> +				input_sync(pcc->input_dev);
> +				input_report_key(pcc->input_dev,
> +						  KEY_ROTATE_LOCK_TOGGLE, 0);
> +				input_sync(pcc->input_dev);
> +				last_toggle = jiffies;
> +			}
> +			return true;
> +		}
> +		/* Not our sequence: replay the buffered genuine Left-GUI make. */
> +		rstate = ROT_IDLE;
> +		serio_interrupt(port, 0xe0, 0);
> +		serio_interrupt(port, 0x5b, 0);
> +		break;
> +	case ROT_WAIT_E5:
> +		if (data == 0xe5) {
> +			rstate = ROT_WAIT_E0B;
> +			return true;
> +		}
> +		rstate = ROT_IDLE;
> +		break;
> +	case ROT_WAIT_E0B:
> +		if (data == 0xe0) {
> +			rstate = ROT_WAIT_DB;
> +			return true;
> +		}
> +		rstate = ROT_IDLE;
> +		break;
> +	case ROT_WAIT_DB:
> +		rstate = ROT_IDLE;
> +		if (data == 0xdb)
> +			return true;
> +		break;
> +	case ROT_IDLE:
> +		break;
> +	}
> +
>  	if (data == 0xe0) {
>  		extended = true;
>  		return true;
> @@ -276,6 +343,19 @@ static bool panasonic_i8042_filter(unsigned char data, unsigned char str,
>  		case 0x2e: /* e0 2e / e0 ae, Volume Down press / release */
>  		case 0x30: /* e0 30 / e0 b0, Volume Up press / release */
>  			return true;
> +		case 0x5b: /* e0 5b, possible start of rotate-lock sequence */
> +			if (data == 0x5b) {
> +				rstate = ROT_WAIT_65;
> +				return true;
> +			}
> +			/*
> +			 * data == 0xdb: genuine Left-GUI/Meta break code.
> +			 * The rotate-lock sequence only ever begins with
> +			 * the make code, so this is a real key release,
> +			 * not our sequence; the code below replays it
> +			 * untouched.
> +			 */
> +			fallthrough;
>  		default:
>  			/*
>  			 * Report the previously filtered e0 before continuing
> @@ -944,6 +1024,9 @@ static int acpi_pcc_init_input(struct pcc_acpi *pcc)
>  		goto err_free_dev;
>  	}
>  
> +	/* Synthesized by panasonic_i8042_filter(), not part of the ACPI keymap. */
> +	input_set_capability(input_dev, EV_KEY, KEY_ROTATE_LOCK_TOGGLE);
> +
>  	error = input_register_device(input_dev);
>  	if (error) {
>  		pr_err("Unable to register input device\n");
> @@ -1090,7 +1173,7 @@ static int acpi_pcc_hotkey_probe(struct platform_device *pdev)
>  		pcc->platform = NULL;
>  	}
>  
> -	i8042_install_filter(panasonic_i8042_filter, NULL);
> +	i8042_install_filter(panasonic_i8042_filter, pcc);
>  	return 0;
>  
>  out_platform:
> 



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