From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 91385C61DB9 for ; Thu, 27 Aug 2026 19:13:00 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id CDAD210F17F; Thu, 27 Aug 2026 19:12:59 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="SYlQ6J1j"; dkim-atps=neutral Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id F2CC010F17F for ; Thu, 27 Aug 2026 19:12:58 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 39AE6600D4; Thu, 27 Aug 2026 19:12:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AE0A51F000E9; Thu, 27 Aug 2026 19:12:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787857977; bh=n/prNACSm7ZD+vf9e96Ht6fX4eX3xVkiLOEXo1W+KBA=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=SYlQ6J1j0JuUZur+PsSqfbunc9x4lITrP7q3r/JSauPA8IfMm3Eswn55v2lEF4frI tPYIvbvgIFBnExt1xkfYIs/GGtWPbpjzUQWTG6QRxMjoi2YGE21Bvz7CrLbX5L/cHt lE/IJ7jMBEChlxxr3/jceWvdBH1kL8yqoCFXDCXGozXk0g8k81PmutWnUphKnpTvUI WK0GndRElaHtb2FFxwvTFlUDO3cduB46IvOQ/TbZhfh7ihr3UcpNBcshogO1fV2lWc pKHza8rYqd1y4kA84X6vk2H6Q9aHFMLfN8ZtPAHqTJgqc9qcZSq5Qn/49aFwZiueS6 8HFZ+M0iWQR9w== From: sashiko-bot@kernel.org Subject: Re: [Patch 5/9]: vt: Amend three Kconfig files To: "Alan Mackenzie" Cc: linux-serial@vger.kernel.org, dri-devel@lists.freedesktop.org In-Reply-To: References: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 27 Aug 2026 19:12:57 +0000 Message-Id: <20260827191257.AE0A51F000E9@smtp.kernel.org> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Thank you for your contribution! Sashiko AI review found 2 potential issue(= s) to consider: - [High] Enabling CONFIG_FB_GLYPH_21BIT changes GLYPH_SZ to 4 globally, bre= aking hardware console drivers (like vgacon) and rotated fbcon drivers that= still hardcode 16-bit screen buffer accesses. - [Medium] FB_GLYPH_21BIT is a generic VT/fbdev feature but is inappropriat= ely placed in the DRM clients menu, unnecessarily restricting its use. -- commit 7b9fb605add2fa8c6f62e8ba79cee762cbcbd24c Author: Alan Mackenzie vt: Amend three Kconfig files Until it becomes clear how to integrate CONFIG_A11Y_BRAILLE_CONSOLE and CONFIG_SPEAKUP, they will remain disabled when CONFIG_FB_GLYPH_21BIT is #defined. [ ... ] > diff --git a/drivers/gpu/drm/clients/Kconfig b/drivers/gpu/drm/clients/Kc= onfig > index 6096c623d9d5b..0ce8c1506eaad 100644 > --- a/drivers/gpu/drm/clients/Kconfig > +++ b/drivers/gpu/drm/clients/Kconfig > @@ -42,6 +42,15 @@ config DRM_FBDEV_EMULATION > =20 > If in doubt, say "Y". > =20 > +config FB_GLYPH_21BIT > + bool "Enable 21-bit glyphs in the frame buffer device" > + depends on (DRM_FBDEV_EMULATION =3D y) [Severity: Medium] Could placing this generic VT/fbdev feature in the DRM clients menu inappropriately restrict its use? Native framebuffer drivers (e.g., vesafb, efifb, simplefb) might be prevent= ed from utilizing 21-bit glyph support, as this strictly requires DRM_FBDEV_EMULATION. The feature modifies the generic Virtual Terminal and fbcon subsystems, which are independent of DRM. [Severity: High] Can enabling CONFIG_FB_GLYPH_21BIT corrupt the screen buffer for hardware console drivers and rotated fbcon drivers? When this is enabled, GLYPH_SZ becomes 4 globally and VT uses 32-bit screen buffer entries. However, the consw interface still passes pointers typed as const unsigned short *, and some drivers still hardcode 16-bit accesses. For example, rotated fbcon implementations iterate the buffer using scr_rea= dw() which advances the u16 pointer by 2 bytes instead of 4, reading half-charac= ters: drivers/video/fbdev/core/fbcon_cw.c:cw_putcs_aligned() { ... src =3D par->rotated.buf + (scr_readw(s++) & charmask) * cellsize; ... } Similarly, vgacon maps physical VGA VRAM assuming exactly 16 bits per chara= cter, meaning 32-bit writes from scr_writeg in vt.c will overwrite adjacent cells in hardware memory: drivers/video/console/vgacon.c:vgacon_invert_region() { ... u16 a =3D scr_readw(p); ... scr_writew(a, p++); ... } > + help > + This option enables 21-bit glyphs in the fbdev framebuffer, > + surmounting the traditional restriction to 256/512 glyphs dating back > + to the VGA hardware of the 1980s and 1990s. To use this effectively > + you will need a suitable font and possibly a suitable keyboard layout. > + --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/apCEDM2sWv_M354-@MA= C.fritz.box?part=3D5