linux-kernel - Re: [PATCH v3 1/2] VT: Add KDFONTINFO ioctl

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Message-ID: <2f8356a5-cf83-47a7-821c-0c0d6804b029@gmx.de>
Date: Fri, 15 Mar 2024 10:15:31 +0100
From: Helge Deller <deller@....de>
To: legion@...nel.org, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Jiri Slaby <jirislaby@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, kbd@...ts.linux.dev,
 linux-api@...r.kernel.org, linux-fbdev@...r.kernel.org,
 linux-serial@...r.kernel.org
Subject: Re: [PATCH v3 1/2] VT: Add KDFONTINFO ioctl

On 3/12/24 15:23, legion@...nel.org wrote:
> From: Alexey Gladkov <legion@...nel.org>
>
> Each driver has its own restrictions on font size. There is currently no
> way to understand what the requirements are. The new ioctl allows
> userspace to get the minmum and maximum font size values.
>
> Signed-off-by: Alexey Gladkov <legion@...nel.org>

Acked-by: Helge Deller <deller@....de>

Helge

> ---
>   drivers/tty/vt/vt.c       | 24 ++++++++++++++++++++++++
>   drivers/tty/vt/vt_ioctl.c | 13 +++++++++++++
>   include/linux/console.h   |  2 ++
>   include/linux/vt_kern.h   |  1 +
>   include/uapi/linux/kd.h   | 13 ++++++++++++-
>   5 files changed, 52 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> index 156efda7c80d..8c2a3d98b5ec 100644
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -4680,6 +4680,30 @@ int con_font_op(struct vc_data *vc, struct console_font_op *op)
>   	return -ENOSYS;
>   }
>
> +int con_font_info(struct vc_data *vc, struct console_font_info *info)
> +{
> +	int rc = -EINVAL;
> +
> +	info->min_height = 0;
> +	info->max_height = max_font_height;
> +
> +	info->min_width = 0;
> +	info->max_width = max_font_width;
> +
> +	info->flags = KD_FONT_INFO_FLAG_LOW_SIZE | KD_FONT_INFO_FLAG_HIGH_SIZE;
> +
> +	console_lock();
> +	if (vc->vc_mode != KD_TEXT)
> +		rc = -EINVAL;
> +	else if (vc->vc_sw->con_font_info)
> +		rc = vc->vc_sw->con_font_info(vc, info);
> +	else
> +		rc = -ENOSYS;
> +	console_unlock();
> +
> +	return rc;
> +}
> +
>   /*
>    *	Interface exported to selection and vcs.
>    */
> diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
> index 8c685b501404..b3b4e4b69366 100644
> --- a/drivers/tty/vt/vt_ioctl.c
> +++ b/drivers/tty/vt/vt_ioctl.c
> @@ -479,6 +479,19 @@ static int vt_k_ioctl(struct tty_struct *tty, unsigned int cmd,
>   		break;
>   	}
>
> +	case KDFONTINFO: {
> +		struct console_font_info fnt_info;
> +
> +		if (copy_from_user(&fnt_info, up, sizeof(fnt_info)))
> +			return -EFAULT;
> +		ret = con_font_info(vc, &fnt_info);
> +		if (ret)
> +			return ret;
> +		if (copy_to_user(up, &fnt_info, sizeof(fnt_info)))
> +			return -EFAULT;
> +		break;
> +	}
> +
>   	default:
>   		return -ENOIOCTLCMD;
>   	}
> diff --git a/include/linux/console.h b/include/linux/console.h
> index 779d388af8a0..5bea6f6c2042 100644
> --- a/include/linux/console.h
> +++ b/include/linux/console.h
> @@ -20,6 +20,7 @@
>   #include <linux/types.h>
>
>   struct vc_data;
> +struct console_font_info;
>   struct console_font_op;
>   struct console_font;
>   struct module;
> @@ -59,6 +60,7 @@ struct consw {
>   			unsigned int lines);
>   	int	(*con_switch)(struct vc_data *vc);
>   	int	(*con_blank)(struct vc_data *vc, int blank, int mode_switch);
> +	int	(*con_font_info)(struct vc_data *vc, struct console_font_info *info);
>   	int	(*con_font_set)(struct vc_data *vc, struct console_font *font,
>   			unsigned int vpitch, unsigned int flags);
>   	int	(*con_font_get)(struct vc_data *vc, struct console_font *font,
> diff --git a/include/linux/vt_kern.h b/include/linux/vt_kern.h
> index c1f5aebef170..6bda4cc1fe6f 100644
> --- a/include/linux/vt_kern.h
> +++ b/include/linux/vt_kern.h
> @@ -32,6 +32,7 @@ void do_blank_screen(int entering_gfx);
>   void do_unblank_screen(int leaving_gfx);
>   void poke_blanked_console(void);
>   int con_font_op(struct vc_data *vc, struct console_font_op *op);
> +int con_font_info(struct vc_data *vc, struct console_font_info *info);
>   int con_set_cmap(unsigned char __user *cmap);
>   int con_get_cmap(unsigned char __user *cmap);
>   void scrollback(struct vc_data *vc);
> diff --git a/include/uapi/linux/kd.h b/include/uapi/linux/kd.h
> index 6b384065c013..781e086e55bf 100644
> --- a/include/uapi/linux/kd.h
> +++ b/include/uapi/linux/kd.h
> @@ -183,8 +183,19 @@ struct console_font {
>
>   #define KD_FONT_FLAG_DONT_RECALC 	1	/* Don't recalculate hw charcell size [compat] */
>
> +#define KDFONTINFO	0x4B73	/* font information */
> +
> +#define KD_FONT_INFO_FLAG_LOW_SIZE	(1U << 0) /* 256 */
> +#define KD_FONT_INFO_FLAG_HIGH_SIZE	(1U << 1) /* 512 */
> +
> +struct console_font_info {
> +	unsigned int min_width, min_height;	/* minimal font size */
> +	unsigned int max_width, max_height;	/* maximum font size */
> +	unsigned int flags;			/* KD_FONT_INFO_FLAG_* */
> +};
> +
>   /* note: 0x4B00-0x4B4E all have had a value at some time;
>      don't reuse for the time being */
> -/* note: 0x4B60-0x4B6D, 0x4B70-0x4B72 used above */
> +/* note: 0x4B60-0x4B6D, 0x4B70-0x4B73 used above */
>
>   #endif /* _UAPI_LINUX_KD_H */