linux-kernel - Re: [PATCH v14] tty: Fix the keyboard led light display problem

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Date:   Tue, 9 Nov 2021 22:41:51 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     lianzhi chang <changlianzhi@...ontech.com>
Cc:     linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        jirislaby@...nel.org, andriy.shevchenko@...ux.intel.com,
        282827961@...com
Subject: Re: [PATCH v14] tty: Fix the keyboard led light display problem

Hi lianzhi,

On Mon, Nov 08, 2021 at 01:51:39PM +0800, lianzhi chang wrote:
> Switching from the desktop environment to the tty environment,
> the state of the keyboard led lights and the state of the keyboard
> lock are inconsistent. This is because the attribute kb->kbdmode
> of the tty bound in the desktop environment (Xorg) is set to
> VC_OFF, which causes the ledstate and kb->ledflagstate

We know that Xorg sets kbdmode mode to VC_OFF, but it does not mean that
you can say for sure that it is Xorg instance that controls a VT simply
by observing kb->kbdmode. There may be something else entirely. That is
why you want drivers/tty/vt/keyboard.c to reset LEDs and leave it to
whoever is controlling VT to set them to something else if it is
desired.

> values of the bound tty to always be 0, which causes the switch
> from the desktop When to the tty environment, the LED light
> status is inconsistent with the keyboard lock status.
> In order to ensure that the keyboard LED lights are displayed
> normally during the VT switching process, when the VT is
> switched, the current VT LED configuration is forced to be issued.
> 
> Signed-off-by: lianzhi chang <changlianzhi@...ontech.com>
> Suggested-by: dmitry.torokhov <dmitry.torokhov@...il.com>
> Suggested-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  v13:
>  The kbd_bh function no longer handles the "kb->kbdmode == VC_OFF"
>  scene, but puts this process in vt_set_leds_compute_shiftstate
>  together. Because the current circumvention is that other ttys
>  switch to the Xorg-bound tty scene, so this Better.
>  v14:
>  Sorry, I forgot to verify the format, it is good now.
>  
>  drivers/tty/vt/keyboard.c | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
> index c7fbbcdcc346..91e1c5d92029 100644
> --- a/drivers/tty/vt/keyboard.c
> +++ b/drivers/tty/vt/keyboard.c
> @@ -153,6 +153,7 @@ static int shift_state = 0;
>  
>  static unsigned int ledstate = -1U;			/* undefined */
>  static unsigned char ledioctl;
> +static bool vt_switch;
>  
>  /*
>   * Notifier list for console keyboard events
> @@ -412,9 +413,20 @@ static void do_compute_shiftstate(void)
>  /* We still have to export this method to vt.c */
>  void vt_set_leds_compute_shiftstate(void)
>  {
> +	struct kbd_struct *kb;
>  	unsigned long flags;
>  
> -	set_leds();
> +	/* Xorg will bind a tty, the kb->kbdmode of this tty will be set to
> +	 * VC_OFF, and this tty will no longer set the keyboard light. If
> +	 * there is no such restriction, when switching from other tty to
> +	 * Xorg-bound tty, the tty will set the keyboard light, which is
> +	 * unreasonable
> +	 */
> +	kb = kbd_table + fg_console;
> +	if (kb->kbdmode != VC_OFF) {
> +		vt_switch = true;
> +		set_leds();
> +	}
>  
>  	spin_lock_irqsave(&kbd_event_lock, flags);
>  	do_compute_shiftstate();
> @@ -1255,6 +1267,11 @@ static void kbd_bh(struct tasklet_struct *unused)
>  	leds |= (unsigned int)kbd->lockstate << 8;
>  	spin_unlock_irqrestore(&led_lock, flags);
>  
> +	if (vt_switch) {
> +		ledstate = ~leds;
> +		vt_switch = false;
> +	}
> +
>  	if (leds != ledstate) {
>  		kbd_propagate_led_state(ledstate, leds);
>  		ledstate = leds;
> -- 
> 2.20.1
> 
> 
> 

Thanks.

-- 
Dmitry