linux-kernel - Re: [PATCH v20] tty: Fix the keyboard led light display problem

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Date:   Mon, 13 Dec 2021 14:15:24 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     lianzhi chang <changlianzhi@...ontech.com>
Cc:     linux-kernel@...r.kernel.org, dmitry.torokhov@...il.com,
        gregkh@...uxfoundation.org, jirislaby@...nel.org, 282827961@...com,
        kernel test robot <lkp@...el.com>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH v20] tty: Fix the keyboard led light display problem

On Mon, Dec 13, 2021 at 02:12:44PM +0800, lianzhi chang wrote:
> Use the "ctrl+alt+Fn" key combination to switch the system from tty to
> desktop or switch the system from desktop to tty. After the switch is
> completed, it is found that the state of the keyboard lock is
> inconsistent with the state of the keyboard Led light.The reasons are
> as follows:
> 
> * The desktop environment (Xorg and other services) is bound to a tty
>   (assuming it is tty1), and the kb->kbdmode attribute value of tty1
>   will be set to VC_OFF. According to the current code logic, in the
>   desktop environment, the values of ledstate and kb->ledflagstate
>   of tty1 will not be modified anymore, so they are always 0.
> 
> * When switching between each tty, the final value of ledstate set by
>   the previous tty is compared with the kb->ledflagstate value of the
>   current tty to determine whether to set the state of the keyboard
>   light. The process of switching between desktop and tty is also the
>   process of switching between tty1 and other ttys. There are two
>   situations:
> 
>   - (1) In the desktop environment, tty1 will not set the ledstate,
>   which will cause when switching from the desktop to other ttys,
>   if the desktop lights up the keyboard's led, after the switch is
>   completed, the keyboard's led light will always be on;
> 
>   - (2) When switching from another tty to the desktop, this
>   mechanism will trigger tty1 to set the led state. If other tty
>   lights up the led of the keyboard before switching to the desktop,
>   the led will be forcibly turned off. This situation should
>   be avoided.
> 
> * Current patch explanation:When VT is switched,the keyboard LED
>   status will be set to the current tty saved value;the value of
>   kb->kbdledctl can be used to confirm whether the current VT
>   can change the status of the keyboard led light;kb->kbdledctl
>   is a new addition,you can use ioctl get or set.
> 
> Signed-off-by: lianzhi chang <changlianzhi@...ontech.com>
> Suggested-by: Dmitry Torokhov <dmitry.torokhov@...il.com>

> Reported-by: kernel test robot <lkp@...el.com>
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>

I believe the original issue hasn't been reported by above mentioned
CIs/people. If you want to give a credit, use changelog for that.

...

> +/**
> + *	vt_do_kdskbledctl

Description?

> + *	@console: the console to use
> + *	@arg: the requested mode
> + *
> + *	Whether to allow the current vt to change the
> + *	keyboard light
> + */

...

> +	struct kbd_struct *kb = &kbd_table[console];
> +	int ret = 0;
> +	unsigned long flags;

Slightly better to read:

	struct kbd_struct *kb = &kbd_table[console];
	unsigned long flags;
	int ret = 0;

...

> +int vt_do_kdgkbledctl(unsigned int console)
> +{
> +	struct kbd_struct *kb = &kbd_table[console];

+ Blank line here. Checkpatch should complain.

> +	/* This is a spot read so needs no locking */
> +	switch (kb->kbdledctl) {
> +	case VC_LEDCTL_ON:
> +		return K_LEDCTL_ON;
> +	case VC_LEDCTL_OFF:
> +		return K_LEDCTL_OFF;

> +		}

Indentation issue.
Consider adding default case.

> +}

...

> +	unsigned char kbdledctl:1； /*Whether to allow to control the led of the keyboard */

Missed space in the comment.

-- 
With Best Regards,
Andy Shevchenko