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Wed, 26 Feb 2025 17:35:11 +0100 Message-ID: <963bba53-2200-4899-b1fd-2cc650990d87@gmx.de> Date: Wed, 26 Feb 2025 17:35:09 +0100 Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/3] dummycon: only build module if there are users To: Arnd Bergmann , Thomas Zimmermann , Arnd Bergmann , Greg Kroah-Hartman Cc: linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org 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> Content-Language: en-US From: Helge Deller Autocrypt: addr=deller@gmx.de; keydata= xsFNBF3Ia3MBEAD3nmWzMgQByYAWnb9cNqspnkb2GLVKzhoH2QD4eRpyDLA/3smlClbeKkWT HLnjgkbPFDmcmCz5V0Wv1mKYRClAHPCIBIJgyICqqUZo2qGmKstUx3pFAiztlXBANpRECgwJ r+8w6mkccOM9GhoPU0vMaD/UVJcJQzvrxVHO8EHS36aUkjKd6cOpdVbCt3qx8cEhCmaFEO6u CL+k5AZQoABbFQEBocZE1/lSYzaHkcHrjn4cQjc3CffXnUVYwlo8EYOtAHgMDC39s9a7S90L 69l6G73lYBD/Br5lnDPlG6dKfGFZZpQ1h8/x+Qz366Ojfq9MuuRJg7ZQpe6foiOtqwKym/zV dVvSdOOc5sHSpfwu5+BVAAyBd6hw4NddlAQUjHSRs3zJ9OfrEx2d3mIfXZ7+pMhZ7qX0Axlq Lq+B5cfLpzkPAgKn11tfXFxP+hcPHIts0bnDz4EEp+HraW+oRCH2m57Y9zhcJTOJaLw4YpTY GRUlF076vZ2Hz/xMEvIJddRGId7UXZgH9a32NDf+BUjWEZvFt1wFSW1r7zb7oGCwZMy2LI/G aHQv/N0NeFMd28z+deyxd0k1CGefHJuJcOJDVtcE1rGQ43aDhWSpXvXKDj42vFD2We6uIo9D 1VNre2+uAxFzqqf026H6cH8hin9Vnx7p3uq3Dka/Y/qmRFnKVQARAQABzRxIZWxnZSBEZWxs ZXIgPGRlbGxlckBnbXguZGU+wsGRBBMBCAA7AhsDBQsJCAcCBhUKCQgLAgQWAgMBAh4BAheA FiEERUSCKCzZENvvPSX4Pl89BKeiRgMFAl3J1zsCGQEACgkQPl89BKeiRgNK7xAAg6kJTPje uBm9PJTUxXaoaLJFXbYdSPfXhqX/BI9Xi2VzhwC2nSmizdFbeobQBTtRIz5LPhjk95t11q0s uP5htzNISPpwxiYZGKrNnXfcPlziI2bUtlz4ke34cLK6MIl1kbS0/kJBxhiXyvyTWk2JmkMi REjR84lCMAoJd1OM9XGFOg94BT5aLlEKFcld9qj7B4UFpma8RbRUpUWdo0omAEgrnhaKJwV8 qt0ULaF/kyP5qbI8iA2PAvIjq73dA4LNKdMFPG7Rw8yITQ1Vi0DlDgDT2RLvKxEQC0o3C6O4 iQq7qamsThLK0JSDRdLDnq6Phv+Yahd7sDMYuk3gIdoyczRkXzncWAYq7XTWl7nZYBVXG1D8 gkdclsnHzEKpTQIzn/rGyZshsjL4pxVUIpw/vdfx8oNRLKj7iduf11g2kFP71e9v2PP94ik3 Xi9oszP+fP770J0B8QM8w745BrcQm41SsILjArK+5mMHrYhM4ZFN7aipK3UXDNs3vjN+t0zi qErzlrxXtsX4J6nqjs/mF9frVkpv7OTAzj7pjFHv0Bu8pRm4AyW6Y5/H6jOup6nkJdP/AFDu 5ImdlA0jhr3iLk9s9WnjBUHyMYu+HD7qR3yhX6uWxg2oB2FWVMRLXbPEt2hRGq09rVQS7DBy dbZgPwou7pD8MTfQhGmDJFKm2jvOwU0EXchrcwEQAOsDQjdtPeaRt8EP2pc8tG+g9eiiX9Sh rX87SLSeKF6uHpEJ3VbhafIU6A7hy7RcIJnQz0hEUdXjH774B8YD3JKnAtfAyuIU2/rOGa/v UN4BY6U6TVIOv9piVQByBthGQh4YHhePSKtPzK9Pv/6rd8H3IWnJK/dXiUDQllkedrENXrZp eLUjhyp94ooo9XqRl44YqlsrSUh+BzW7wqwfmu26UjmAzIZYVCPCq5IjD96QrhLf6naY6En3 ++tqCAWPkqKvWfRdXPOz4GK08uhcBp3jZHTVkcbo5qahVpv8Y8mzOvSIAxnIjb+cklVxjyY9 dVlrhfKiK5L+zA2fWUreVBqLs1SjfHm5OGuQ2qqzVcMYJGH/uisJn22VXB1c48yYyGv2HUN5 lC1JHQUV9734I5cczA2Gfo27nTHy3zANj4hy+s/q1adzvn7hMokU7OehwKrNXafFfwWVK3OG 1dSjWtgIv5KJi1XZk5TV6JlPZSqj4D8pUwIx3KSp0cD7xTEZATRfc47Yc+cyKcXG034tNEAc xZNTR1kMi9njdxc1wzM9T6pspTtA0vuD3ee94Dg+nDrH1As24uwfFLguiILPzpl0kLaPYYgB wumlL2nGcB6RVRRFMiAS5uOTEk+sJ/tRiQwO3K8vmaECaNJRfJC7weH+jww1Dzo0f1TP6rUa fTBRABEBAAHCwXYEGAEIACAWIQRFRIIoLNkQ2+89Jfg+Xz0Ep6JGAwUCXchrcwIbDAAKCRA+ Xz0Ep6JGAxtdEAC54NQMBwjUNqBNCMsh6WrwQwbg9tkJw718QHPw43gKFSxFIYzdBzD/YMPH l+2fFiefvmI4uNDjlyCITGSM+T6b8cA7YAKvZhzJyJSS7pRzsIKGjhk7zADL1+PJei9p9idy RbmFKo0dAL+ac0t/EZULHGPuIiavWLgwYLVoUEBwz86ZtEtVmDmEsj8ryWw75ZIarNDhV74s BdM2ffUJk3+vWe25BPcJiaZkTuFt+xt2CdbvpZv3IPrEkp9GAKof2hHdFCRKMtgxBo8Kao6p Ws/Vv68FusAi94ySuZT3fp1xGWWf5+1jX4ylC//w0Rj85QihTpA2MylORUNFvH0MRJx4mlFk XN6G+5jIIJhG46LUucQ28+VyEDNcGL3tarnkw8ngEhAbnvMJ2RTx8vGh7PssKaGzAUmNNZiG MB4mPKqvDZ02j1wp7vthQcOEg08z1+XHXb8ZZKST7yTVa5P89JymGE8CBGdQaAXnqYK3/yWf FwRDcGV6nxanxZGKEkSHHOm8jHwvQWvPP73pvuPBEPtKGLzbgd7OOcGZWtq2hNC6cRtsRdDx 4TAGMCz4j238m+2mdbdhRh3iBnWT5yPFfnv/2IjFAk+sdix1Mrr+LIDF++kiekeq0yUpDdc4 ExBy2xf6dd+tuFFBp3/VDN4U0UfG4QJ2fg19zE5Z8dS4jGIbLg== In-Reply-To: <79d35e3b-9a0d-41a5-ab07-797bfa1e19cb@app.fastmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:WlwvLQn6df8JcLdlvcWq7rno/4sg4CpGNOv4Y382KCAq3uQQ55a xC88qCSAj92I4gZnmiVVc7MWtUNIxkGivdkN5HijJ4ZWECoh7JY7xGLUsrz4V6jUAPQ2OHd m9KY7Y3cL3rhoCNz+JgYRGR2wu2mSQuGjUxYN01xCmN/xqSRT1Acm+kJtqkNjpSFlzLoz7u x2VdWNSMJYjZWPtVw419g== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:KrTJI3/m7BQ=;cC3w3XecgT8H0f8Xku0kj2e6Km4 i1f6zfqL+TE9PbOEzRQY/j+FG9G3/j1kl5REfAh6pXOeGFz011yhd892xGaB1pmlaG+UeCBBK 2B7RFNSZF3rUKHHRlunOxfdLnEcuRO8FQ4wQFUZfY6SMJrt0/ayDBNHaZ5iRFgv2XXRd1ZZ+w fq51H0e3vpd+6jdil25dWn5l33KB45DX8AlyN726YCeXstDP4ReLgACmXZmGDTIVwszWU9S1F TshsoIkUnj6c+heuAqrFwlc04kmmKnpIL1X5vN0kLHX686Ae4DI4wQcTWZ9qR8tZhoIF522Xv Xa9dzIs3Bidn/la/W6oR68kGdUDgSltWCWDFqbUj/LDX/9NQvu6P+WfuyCeuzZ3vVgoz2JHwI QZqbXSBLzAucaIpWKeBCqdHjMMc0jZ5Ocm/yOrKkAcDwRRheSFcBbIgIRaUr3CYF9tl4sc4gI Gsc0gO08EdL+aoAgJ/iExCXqice3D1zWzKXUFUf2YqXLRSJ+b107ssq+SOgdrUvn5YBonFP5N IACK+dv7b6HAF5BekpsSDRGjA/7spgsjwGOBd9Y3cC3NteBVOMI6ncGKzYXuV3O7F5U8Jst/C T/zB+IpKtQeotSdikrxp3cFb4vKAL3KmJp5dSiy7vC/g+h7QjuAkfSjW8jPl6AzexnWRi2uOv lsyqb98Ue3FJZFpLSSdoDH51G151KaFXCoh/hpgw0f5OWWtwKmWDLHwUXgPEgY5pnb8pNSKy8 RmU7aemYfObL+24gOBmBO8lT9vVSWxdIKc/tgxBweqpF3YesdT7jJtj8fBl9h81AkTRXLQCz7 l2nL8M6tCVorRRsgIhWLNkMDeVJsWuwJsGBvijGNZBnimPuVQo9+3g4z56iITn54x21XwZ6Rt prsW/HWKwP3s1/Ni8UYVg5avkee2RFb4LLEZt8TE5c9um+yEWynl9vsfAm9/saVMzzqVhqfLM eCzQPYnQj35j+bKvvIbDQXzxFJWydVHxTWJXHHdUR/JU21r3fKUvsijDySxo6xw/JHffX+Ol6 K/TFdTIX2i5N1wxfwmzAb4zOgDA86Co/1xfo2MM2kCNSo0Or7XdxfaexK7m0NE+HNa7Zd1jau 2KC+qnQPetiCKDORIj2CTUujxipZLbfyWqYDb8uuX3Aa7TGI5d6j+aBJj051Ia5zLZWzsL4KS YH0qlJEdpeFQ0M3j6tOTQTIONvVBM8/4JzVy+yuPeBWhULnAogQ3qUAzWJ+QaA0AN1NO1aud/ jAbXvfaeNdpLBn88QPW0vWGdvNT4Pp3izYGc2MuNbkAvyxwPSQ4R4CivFBNdmD5NGYzRBB2QC j8RaM3VeeeaOdeeVjzKQAxltXz3/oqYXIRzl2pjBWLofolDuUrjhfEOJ66GJSYTua6jIzbpQu btE7/HMSUyFavYTjzH/o264jF9ir6rShVDNKl9HkpYaqtqL8CNIdpgYkuC On 2/26/25 12:46, Arnd Bergmann wrote: > 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=3Dy. Wouldn't it make sense to have them depend on CONFIG_VT= =3Dy? >> 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 probabl= y >> 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). Yes, it's rare. But on parisc, if no supported fbdev or drm graphic card is found, it needs to stays on sticon (which always works). Otherwise - if a card was found - the kernel switches dynamically to fbcon= . > If we do this, the conswitchp code could be merged with dummycon > in drivers/video/console, with the simpler alternative just > calling into fbcon functions. As mentioned above, that should be optional then. > 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. Helge