linux-kernel - Re: [PATCH v3] simplefb: Enable boot time VESA graphic mode selection.

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Date:   Wed, 23 Feb 2022 17:45:28 +0100
From:   Michal Suchánek <msuchanek@...e.de>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Martin Mares <mj@....cz>,
        Helge Deller <deller@....de>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Cristian Marussi <cristian.marussi@....com>,
        Simon Trimmer <simont@...nsource.cirrus.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rob Herring <robh@...nel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        David Herrmann <dh.herrmann@...il.com>,
        linux-kernel@...r.kernel.org, linux-video@...ey.karlin.mff.cuni.cz
Subject: Re: [PATCH v3] simplefb: Enable boot time VESA graphic mode
 selection.

On Wed, Feb 23, 2022 at 05:34:50PM +0100, Javier Martinez Canillas wrote:
> Hello Michal,
> 
> On 2/18/22 17:04, Michal Suchanek wrote:
> > Since switch to simplefb/simpledrm VESA graphic modes are no longer
> > available with legacy BIOS.
> 
> Maybe you can mention that is the "vga=" kernel command line parameter
> since that may be more evident to people reading the commit message ?

Yes, I suppose that could be added.

> > The x86 realmode boot code enables the VESA graphic modes when option
> > FB_BOOT_VESA_SUPPORT is enabled.
> > 
> > To enable use of VESA modes with simplefb in legacy BIOS boot mode drop
> 
> I think you meant "VESA modes with the sysfb driver" ? or something like
> that since otherwise it seems that you meant to use it with the simplefb
> (drivers/video/fbdev/simplefb.c) fbdev driver, which doesn't support the
> "vga=" param as far as I understand (it just uses whatever was setup).

And the vga= is whatever was set up by the realmode code. And the config
option for realmode code to do that is selected by vesafb and not
simplefb so it does not wotk for simplefb/simpledrm/whatewer when efifib
is not built into the kernel.

> The name sysfb_simplefb is really horrible, because it is too confusing
> and probably we should change it at some point...
> 
> Patch itself looks good to me though.
> 
> Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>

Thanks

Michal