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[62.151.111.63]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43aba5871f4sm19373245e9.39.2025.02.26.04.05.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Feb 2025 04:05:26 -0800 (PST) From: Javier Martinez Canillas To: Arnd Bergmann , 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 Subject: Re: [PATCH 1/3] dummycon: only build module if there are users In-Reply-To: <79d35e3b-9a0d-41a5-ab07-797bfa1e19cb@app.fastmail.com> 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> Date: Wed, 26 Feb 2025 13:05:23 +0100 Message-ID: <87mse8zzb0.fsf@minerva.mail-host-address-is-not-set> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain "Arnd Bergmann" writes: Hello Arnd, > On Wed, Feb 26, 2025, at 09:16, Thomas Zimmermann wrote: >> Am 26.02.25 um 08:55 schrieb Arnd Bergmann: >> Here's another general question. vgacon and fbcon only seem usable with >> CONFIG_VT=y. Wouldn't it make sense to have them depend on CONFIG_VT=y? >> dummycon could then be implemented as part of the vt code, maybe even >> become a vt-internal thing. The console code is complex, so I'm probably >> missing something here? > > I think in theory one may have a system use fbcon purely to get the > boot logo, but not actually support VT. I had also assumed there might > be a way to use fbcon as the console (i.e. printk) but not register > the tty, but it looks like the console code still requires vt. > > After I looked at the vt and conswitchp code some more, I wonder > if we could go the other way and instead of integrating it more > make the conswitchp logic optional: most of the complexity here > deals with switching between text console and fbcon dynamically, > but having any text console support is getting very rare (vga > on alpha/mips/x86-32, newport on mips-ip22, sti on parisc). > > If we do this, the conswitchp code could be merged with dummycon This sounds like a much better approach indeed. > 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. > Arnd > -- Best regards, Javier Martinez Canillas Core Platforms Red Hat