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Thu, 13 Jun 2024 23:30:07 +0200 Message-ID: <5d8d2efe-45dd-4033-aaae-e7f923ef9e76@gmx.de> Date: Thu, 13 Jun 2024 23:30:06 +0200 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] fbdev: vesafb: Detect VGA compatibility from screen info's VESA attributes To: Thomas Zimmermann , sam@ravnborg.org, javierm@redhat.com, hpa@zytor.com Cc: linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, stable@vger.kernel.org References: <20240613090240.7107-1-tzimmermann@suse.de> 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: <20240613090240.7107-1-tzimmermann@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:CIvh9Sq72L3aovFbBuEWTa4wKFZV9W+x9cxqUQ8VJu0dwiyxIaQ D0sNDRFtQ2uX2wwcTld99nDRnvqMI4nGSeeRJ6mp/PnR8E2Aui1TeHw4LQ+YAalIYT8Nle+ F2Olcm6+bAdLwagza6TxZ04EK7t0+cTr+/IkL9kNGU1o3x9zaijtTJ6bz4wwNb4Rf9Dbc/J 0iQ0YxVupLdgzzHy0CFBQ== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:mXuTNfgv1qc=;zGblu22QTNPoMbN62vu9nOvUy40 Wl2fHNKqexYS2cqveLq3ZE8WMNdPifAkR2xv9uVlaLn6QSuqKDlaXT6X8qOXMGntS/vFqYpLG RgyHQlleIAGQiUlIcy71GNRFfWUBVZTs3Y3ZOLEePXg55EJ7CcPIFzWdOSbYLsZDNooKH8Y10 gpcCxhVAYIU7TJbe5md19NmR6Su4uE+oXc+K/9NX1nWe1kBSiF/vk7PhYfKU1SYm7c11tBm26 GKhJL3B/Ts2zATfB6DHtoOW9jKhmvwdvgISQGHZHfIDMfUdfYvP6ohVeJGJQNiQAJHXVjYh0V Ir7nbGkRnbLDCtTJUyem0pwhRhSEYQE/KwtOpXSRJxuHPcptsh9tibTJa3HC+1mga86C00lY4 wM9EdSwhpqAbYmZGZ6Uqkc7nBiBdFeKG9CNwkVTNEjMTzmgKe5GsLCNr9P47mcAh6/tgm8FTH LHJv/B36VPb1BfmmZo4s6uUxBNPRRPdbmHj8HY+2dSCINCJ2D+n90vh28ZG/btbl5nYUAzRCo onu0ogYuSxr3y7seDMhYMkLl+2gu7nwltfpTzICZEg2pUcNfVjKwJAp8wPXM5p1Xe2e+JzV/L tr8HBAGHxayzNRmt/2xbJ6IywWZ7Zp39I9t1rB/yGTh6m7lrO1AKu9DZBh9vHZ2DD8hORtZe7 VzDgpBvwfYKSaaT3Z/5OII7VR9m/T/HgqGXGtSlQR3RVuaruBe9biiyIFQjfsUE3B6sWdiDY1 4epVM1UO2YZ7iZFfTrpzZaoj0J6o9NUZs/TjZ8ZBUnpxP7f24PsSlcigF7nlVD+s11cgkO+/x OXMwY/QYWqv8g4y/ZfLzdtpmyHmj6WGRsrI5WZICHI7HU= On 6/13/24 11:02, Thomas Zimmermann wrote: > Test the vesa_attributes field in struct screen_info for compatibility > with VGA hardware. Vesafb currently tests bit 1 in screen_info's > capabilities field, It sets the framebuffer address size and is > unrelated to VGA. > > Section 4.4 of the Vesa VBE 2.0 specifications defines that bit 5 in > the mode's attributes field signals VGA compatibility. The mode is > compatible with VGA hardware if the bit is clear. In that case, the > driver can access VGA state of the VBE's underlying hardware. The > vesafb driver uses this feature to program the color LUT in palette > modes. Without, colors might be incorrect. > > The problem got introduced in commit 89ec4c238e7a ("[PATCH] vesafb: Fix > incorrect logo colors in x86_64"). It incorrectly stores the mode > attributes in the screen_info's capabilities field and updates vesafb > accordingly. Later, commit 5e8ddcbe8692 ("Video mode probing support for > the new x86 setup code") fixed the screen_info, but did not update vesaf= b. > Color output still tends to work, because bit 1 in capabilities is > usually 0. > > Besides fixing the bug in vesafb, this commit introduces a helper that > reads the correct bit from screen_info. Nice catch, Thomas! But do we really need this additional helper? > > Signed-off-by: Thomas Zimmermann > Fixes: 5e8ddcbe8692 ("Video mode probing support for the new x86 setup c= ode") > Cc: # v2.6.23+ > --- > drivers/video/fbdev/vesafb.c | 2 +- > include/linux/screen_info.h | 5 +++++ > 2 files changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/video/fbdev/vesafb.c b/drivers/video/fbdev/vesafb.c > index 8ab64ae4cad3e..5a161750a3aee 100644 > --- a/drivers/video/fbdev/vesafb.c > +++ b/drivers/video/fbdev/vesafb.c > @@ -271,7 +271,7 @@ static int vesafb_probe(struct platform_device *dev) > if (si->orig_video_isVGA !=3D VIDEO_TYPE_VLFB) > return -ENODEV; > > - vga_compat =3D (si->capabilities & 2) ? 0 : 1; > + vga_compat =3D !__screen_info_vbe_mode_nonvga(si); Instead maybe just this: ? + /* mode is VGA-compatible if BIT 5 is _NOT_ set */ + vga_compat =3D (si->vesa_attributes & BIT(5)) =3D=3D 0; I suggest to make patch small, esp. if you ask for backport to v2.6.23+. Helge > vesafb_fix.smem_start =3D si->lfb_base; > vesafb_defined.bits_per_pixel =3D si->lfb_depth; > if (15 =3D=3D vesafb_defined.bits_per_pixel) > diff --git a/include/linux/screen_info.h b/include/linux/screen_info.h > index 75303c126285a..95f2a339de329 100644 > --- a/include/linux/screen_info.h > +++ b/include/linux/screen_info.h > @@ -49,6 +49,11 @@ static inline u64 __screen_info_lfb_size(const struct= screen_info *si, unsigned > return lfb_size; > } > > +static inline bool __screen_info_vbe_mode_nonvga(const struct screen_in= fo *si) > +{ > + return si->vesa_attributes & BIT(5); // VGA if _not_ set > +} > + > static inline unsigned int __screen_info_video_type(unsigned int type) > { > switch (type) {