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

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Message-ID: <tencent_032E4FE80FDB8EA164AE0644@qq.com>
Date:   Wed, 10 Nov 2021 15:26:12 +0800
From:   "lianzhi chang" <changlianzhi@...ontech.com>
To:     "dmitry.torokhov" <dmitry.torokhov@...il.com>
Cc:     "linux-kernel" <linux-kernel@...r.kernel.org>,
        "Greg KH" <gregkh@...uxfoundation.org>,
        "jirislaby" <jirislaby@...nel.org>,
        "Andy Shevchenko" 
        <andriy.shevchenko@...ux.intel.com>,
        "282827961" <282827961@...com>
Subject: Re: [PATCH v14] tty: Fix the keyboard led light display problem

> 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.

Does this mean let me change the description information? Or is the
judgment of VC_OFF in patch incorrect?
The setup method of Xorg mentioned here is just to describe a process
in which I found the problem;
My understanding is that when the mode of kbdmode is set to VC_OFF,
VT shouldn't interfere with the state of the keyboard light, right? This is 
how functions such as kbd_keycode() are implemented.
When VT is switched, if the VT mode is VC_OFF, there is also no need
to set the state of the keyboard light. I think this is reasonable.

> > 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.
--
lianzhi chang