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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5B6D3C77B61 for ; Thu, 13 Apr 2023 16:24:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230170AbjDMQYU (ORCPT ); Thu, 13 Apr 2023 12:24:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34012 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230131AbjDMQYR (ORCPT ); Thu, 13 Apr 2023 12:24:17 -0400 Received: from mailbackend.panix.com (mailbackend.panix.com [166.84.1.89]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 43806A5ED for ; Thu, 13 Apr 2023 09:24:14 -0700 (PDT) Received: from mail.panix.com (localhost [127.0.0.1]) by mailbackend.panix.com (Postfix) with ESMTPA id 4Py4f40vJzz4Nr7; Thu, 13 Apr 2023 12:24:12 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=panix.com; s=panix; t=1681403052; bh=f0+jlX/rdABvKTEWjC1C1HcKJCp0LgDbRDXkroLCAb8=; h=In-Reply-To:References:Date:Subject:From:To:Cc; b=h76lDEg0sRQ4cO6vBJ6SUCEuRmhlvg3FkbVuZtjLebQ5sH0ki0XA/QpaXwCiyYdl3 OzyV6yOm0aYrlyxxWT1UQZ0VgaoFyB1/XxW43DGE1E9fMFFdp3pZrx9U8pzRH3MNyt t8oaowB6lnsLO33WNZmrjpDbsXQy9oqGvF9buU2s= X-Panix-Received: from 166.84.1.3 (SquirrelMail authenticated user pa@panix.com) by mail.panix.com with HTTP; Thu, 13 Apr 2023 12:24:12 -0400 Message-ID: In-Reply-To: <87o7nsuumt.fsf@minerva.mail-host-address-is-not-set> References: <20230412150225.3757223-1-javierm@redhat.com> <2e07f818ccdff7023a060e732d7c4ef6.squirrel@mail.panix.com> <87jzyhror0.fsf@minerva.mail-host-address-is-not-set> <1afd3044c2aca9322ecf304941c7df66.squirrel@mail.panix.com> <87fs94stgw.fsf@minerva.mail-host-address-is-not-set> <87cz48srs4.fsf@minerva.mail-host-address-is-not-set> <40edb0fdb0eaff434f4872dd677923a6.squirrel@mail.panix.com> <87a5zcsqg8.fsf@minerva.mail-host-address-is-not-set> <9e6fff69b09b36cbdd96499cd0015154.squirrel@mail.panix.com> <4PxhQn3zK1zcbc@panix1.panix.com> <87o7nsuumt.fsf@minerva.mail-host-address-is-not-set> Date: Thu, 13 Apr 2023 12:24:12 -0400 Subject: Re: [PATCH] firmware/sysfb: Fix wrong stride when bits-per-pixel is calculated From: "Pierre Asselin" To: "Javier Martinez Canillas" Cc: "Pierre Asselin" , tzimmermann@suse.de, linux-kernel@vger.kernel.org, jfalempe@redhat.com, hdegoede@redhat.com, dri-devel@lists.freedesktop.org, daniel.vetter@ffwll.ch, ardb@kernel.org User-Agent: SquirrelMail/1.4.23-p1 MIME-Version: 1.0 Content-Type: text/plain;charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-Priority: 3 (Normal) Importance: Normal Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > pa@panix.com (Pierre Asselin) writes: > >> After careful reading of the comments in f35cd3fa7729, would this >> be an appropriate fix ? Does it still address all the issues raised >> by Thomas ? >> >> (not tested) >> >> diff --git a/drivers/firmware/sysfb_simplefb.c >> b/drivers/firmware/sysfb_simplefb.c >> index 82c64cb9f531..9f5299d54732 100644 >> --- a/drivers/firmware/sysfb_simplefb.c >> +++ b/drivers/firmware/sysfb_simplefb.c >> @@ -56,10 +56,11 @@ __init bool sysfb_parse_mode(const struct >> screen_info *si, >> * don't specify alpha channels. >> */ >> if (si->lfb_depth > 8) { >> - bits_per_pixel = max(max3(si->red_size + si->red_pos, >> + bits_per_pixel = max3(max3(si->red_size + si->red_pos, >> si->green_size + si->green_pos, >> si->blue_size + si->blue_pos), >> - si->rsvd_size + si->rsvd_pos); >> + si->rsvd_size + si->rsvd_pos, >> + si->lfb_depth); > I would defer to Thomas but personally I don't like it. Seems to me that > this is getting too complicated just to workaround buggy BIOS that are not > reporting consistent information about their firmware-provided > framebuffer. Okay, but remember, this is a regression. The buggy BIOSes were there the whole time and the old code that matched f->bits_per_pixel against si->lfb_depth used to work against these buggy BIOSes. And is it a bug, or is it an underspecified standard ? "These bits aren't reserved, we just ignore them" or some such. My reading of Thomas' comments in the code was that sometimes lfb_depth was reported too small but never too large ? But I'm not sure. It's true in my two cases. > I would either trust the pixel channel information (what Thomas patch did) > + my patch to calculate the stride (since we can't trust the line lenght > which is based on the reported depth) + a DMI table for broken machines. > But that will only work if your systems are the exception and not a common > issue, otherwise then Thomas' approach won't work if there are too many > buggy BIOS out there. The laptop is ancient but the Dell tower is maybe 4 years old. The BIOS is 09/11/2019 according to dmidecode, and the most recent for this box. > Another option is to do the opposite, not calculate a BPP using the pixel > and then use that value to calculate a new stride, but instead assume that > the lfb_linelength is correct and use that to calculate the BPP. Or reject (some) inconsistencies in the struct screen_info and return false, so the kernel falls back to e.g. vesa ? > Something like the following patch, which should also fix your regression > and may be enough to address Thomas' concerns of inconsistent depths too? I'll try that patch.