linux-kernel - Re: [Nouveau] [RFC, drm-misc-next v4 0/9] PCI/VGA: Allowing the user to select the primary video adapter at boot time

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Message-ID: <abf8053d-4c4a-2562-b57f-db92a0cb15a7@loongson.cn>
Date:   Wed, 6 Sep 2023 11:08:19 +0800
From:   suijingfeng <suijingfeng@...ngson.cn>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        Sui Jingfeng <sui.jingfeng@...ux.dev>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Daniel Vetter <daniel@...ll.ch>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     nouveau@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-pci@...r.kernel.org
Subject: Re: [Nouveau] [RFC, drm-misc-next v4 0/9] PCI/VGA: Allowing the user
 to select the primary video adapter at boot time

Hi,

On 2023/9/5 23:05, Thomas Zimmermann wrote:
> However, on modern Linux systems the primary display does not really 
> exist. 'Primary' is the device that is available via VGA, VESA or EFI. 

I may miss the point, what do you means by choose the word "modern"?
Are you trying to tell me that X server is too old and Wayland is the modern display server?

> Our drivers don't use these interfaces, but the native registers.

Yes and no?

Yes for the machine with the UEFI firmware,
but I not sure if this statement is true for the machine with the legacy firmware.

As the display controller in the ASpeed BMC is VGA compatible.
Therefore, in theory, it should works with the VGA console on the machine
with another VGA compatible video card. So the ast_vga_set_decode() function
provided in the 0007 patch probably useful on legacy firmware environment.

To be honest, I have tested this on various machine with UEFI firmware.
But I didn't realized that I should do the testing on legacy firmware environment
before sending this patch. It seems that the testing effort needed are quite
exhausting, since all my machines come with the UEFI firmware.

So is it OK to leave the legacy part to someone else who interested in it?
Probably Alex is more professional at legacy VGA routing stuff?
:-)