linux-kernel - Re: [PATCH v2 5/9] vgacon: remove screen

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Date:   Wed, 19 Jul 2023 15:49:22 +0200
From:   Philippe Mathieu-Daudé <philmd@...aro.org>
To:     Arnd Bergmann <arnd@...nel.org>, linux-fbdev@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Helge Deller <deller@....de>,
        Javier Martinez Canillas <javierm@...hat.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        "David S. Miller" <davem@...emloft.net>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Borislav Petkov <bp@...en8.de>, Brian Cain <bcain@...cinc.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Daniel Vetter <daniel@...ll.ch>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        Deepak Rawat <drawat.floss@...il.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guo Ren <guoren@...nel.org>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        Khalid Aziz <khalid@...ehiking.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Matt Turner <mattst88@...il.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Russell King <linux@...linux.org.uk>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        WANG Xuerui <kernel@...0n.name>, Wei Liu <wei.liu@...nel.org>,
        Will Deacon <will@...nel.org>, x86@...nel.org,
        linux-alpha@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-efi@...r.kernel.org,
        linux-csky@...r.kernel.org, linux-hexagon@...r.kernel.org,
        linux-ia64@...r.kernel.org, loongarch@...ts.linux.dev,
        linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-hyperv@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2 5/9] vgacon: remove screen_info dependency

Hi Arnd,

On 19/7/23 14:39, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> The vga console driver is fairly self-contained, and only used by
> architectures that explicitly initialize the screen_info settings.
> 
> Chance every instance that picks the vga console by setting conswitchp
> to call a function instead, and pass a reference to the screen_info
> there.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>   arch/alpha/kernel/setup.c      |  2 +-
>   arch/arm/kernel/setup.c        |  2 +-
>   arch/ia64/kernel/setup.c       |  2 +-
>   arch/mips/kernel/setup.c       |  2 +-
>   arch/x86/kernel/setup.c        |  2 +-
>   drivers/firmware/pcdp.c        |  2 +-
>   drivers/video/console/vgacon.c | 68 ++++++++++++++++++++--------------
>   include/linux/console.h        |  7 ++++
>   8 files changed, 53 insertions(+), 34 deletions(-)


> @@ -1074,13 +1077,13 @@ static int vgacon_resize(struct vc_data *c, unsigned int width,
>   		 * Ho ho!  Someone (svgatextmode, eh?) may have reprogrammed
>   		 * the video mode!  Set the new defaults then and go away.
>   		 */
> -		screen_info.orig_video_cols = width;
> -		screen_info.orig_video_lines = height;
> +		vga_si->orig_video_cols = width;
> +		vga_si->orig_video_lines = height;
>   		vga_default_font_height = c->vc_cell_height;
>   		return 0;
>   	}
> -	if (width % 2 || width > screen_info.orig_video_cols ||
> -	    height > (screen_info.orig_video_lines * vga_default_font_height)/
> +	if (width % 2 || width > vga_si->orig_video_cols ||
> +	    height > (vga_si->orig_video_lines * vga_default_font_height)/
>   	    c->vc_cell_height)
>   		return -EINVAL;
>   
> @@ -1110,8 +1113,8 @@ static void vgacon_save_screen(struct vc_data *c)
>   		 * console initialization routines.
>   		 */
>   		vga_bootup_console = 1;
> -		c->state.x = screen_info.orig_x;
> -		c->state.y = screen_info.orig_y;
> +		c->state.x = vga_si->orig_x;
> +		c->state.y = vga_si->orig_y;

Not really my area, so bare with me if this is obviously not
possible :) If using DUMMY_CONSOLE, can we trigger a save_screen
/ resize? If so, we'd reach here with vga_si=NULL.

>   	}
>   
>   	/* We can't copy in more than the size of the video buffer,
> @@ -1204,4 +1207,13 @@ const struct consw vga_con = {
>   };
>   EXPORT_SYMBOL(vga_con);
>   
> +void vgacon_register_screen(struct screen_info *si)
> +{
> +	if (!si || vga_si)
> +		return;
> +
> +	conswitchp = &vga_con;
> +	vga_si = si;
> +}