linux-kernel - Re: [PATCH 2/2] vt: add TIOCL_GETCURSORPOS to retrieve the screen cursor position

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Message-ID: <518b6620-bca0-45e4-8c1f-6cd9ab18bee2@kernel.org>
Date: Wed, 14 May 2025 07:57:54 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Nicolas Pitre <nico@...xnic.net>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Nicolas Pitre <npitre@...libre.com>, linux-serial@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] vt: add TIOCL_GETCURSORPOS to retrieve the screen
 cursor position

On 14. 05. 25, 3:52, Nicolas Pitre wrote:
...
> So let's work around this limitation by adding TIOCL_GETCURSORPOS as a
> fallback method to get the cursor position when /dev/vcsa reports 255.
...
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
...
> +/* invoked via ioctl(TIOCLINUX) */
> +static int get_cursor_pos(struct tty_struct *tty)
> +{
> +	struct vc_data *vc = tty->driver_data;
> +	unsigned int x, y;
> +
> +	console_lock();
> +	x = vc->state.x;
> +	y = vc->state.y;
> +	console_unlock();
> +
> +	/*
> +	 * Clamp x to 16 bits, y to 15 bits. A display larger than 65535x32767
> +	 * characters won't be a concern for the foreseeable future.
> +	 * Bit 31 is reserved to represent negative error codes elsewhere.
> +	 */
> +	return min(x, 0xFFFFu) | (min(y, 0x7FFFu) << 16);

Hmm, I would do a proper struct instead. Like winsize.

> --- a/include/uapi/linux/tiocl.h
> +++ b/include/uapi/linux/tiocl.h
> @@ -38,4 +38,8 @@ struct tiocl_selection {
>   #define TIOCL_GETKMSGREDIRECT	17	/* get the vt the kernel messages are restricted to */
>   #define TIOCL_GETBRACKETEDPASTE	18	/* get whether paste may be bracketed */
>   
> +#define TIOCL_GETCURSORPOS	20	/* Get screen cursor position */

The same question about man-pages :).

thanks,
-- 
js
suse labs