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Wed, 26 Feb 2025 08:19:06 -0500 (EST) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Wed, 26 Feb 2025 14:18:46 +0100 From: "Arnd Bergmann" To: "Javier Martinez Canillas" , "Thomas Zimmermann" , "Arnd Bergmann" , "Greg Kroah-Hartman" , "Helge Deller" Cc: linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Message-Id: <98ed694b-0f2f-4bfb-9280-729842d9f95c@app.fastmail.com> In-Reply-To: <87mse8zzb0.fsf@minerva.mail-host-address-is-not-set> References: <20250225164436.56654-1-arnd@kernel.org> <4d047af3-fd30-4fa4-aa3d-c0359856d750@suse.de> <29ecc7c4-2887-4989-a1d3-aa76b44c0387@suse.de> <79d35e3b-9a0d-41a5-ab07-797bfa1e19cb@app.fastmail.com> <87mse8zzb0.fsf@minerva.mail-host-address-is-not-set> Subject: Re: [PATCH 1/3] dummycon: only build module if there are users Content-Type: text/plain Content-Transfer-Encoding: 7bit On Wed, Feb 26, 2025, at 13:05, Javier Martinez Canillas wrote: > "Arnd Bergmann" writes: >> in drivers/video/console, with the simpler alternative just >> calling into fbcon functions. I'm not sure if we can already drop >> vgacon from normal x86-64 distro configs, i.e. if there are cases >> that are not already covered by any of efi-earlycon, efifb, >> vga16fb, vesafb/uvesafb or a PCI DRM driver. >> > > I believe vgacon is still useful for x86 with legacy BIOS, because > vesafb (and simpledrm) only works if the user defines a mode using > the vga= kernel cmdline parameter. Right, at the minimum, a configuration without vgacon would have to pick a graphical mode in arch/x86/boot/video*.c if one wasn't already set by grub. Looking through the git history of that code, it seems that there are lots of corner cases with weird 32-bit hardware. Anything from the past 20 years is probably reasonably safe, but there still needs to be a way to configure vgacon back in to be safe. Arnd