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 1C6B9C7EE29 for ; Fri, 9 Jun 2023 17:43:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230012AbjFIRn5 (ORCPT ); Fri, 9 Jun 2023 13:43:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50080 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229503AbjFIRny (ORCPT ); Fri, 9 Jun 2023 13:43:54 -0400 Received: from 189.cn (ptr.189.cn [183.61.185.102]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id E6B5E35B3; Fri, 9 Jun 2023 10:43:44 -0700 (PDT) HMM_SOURCE_IP: 10.64.8.43:47690.1937665454 HMM_ATTACHE_NUM: 0000 HMM_SOURCE_TYPE: SMTP Received: from clientip-114.242.206.180 (unknown [10.64.8.43]) by 189.cn (HERMES) with SMTP id AEDBE100212; Sat, 10 Jun 2023 01:43:39 +0800 (CST) Received: from ([114.242.206.180]) by gateway-151646-dep-75648544bd-7vx9t with ESMTP id 0877e90f4b584cbe94a878d807b39f22 for helgaas@kernel.org; Sat, 10 Jun 2023 01:43:43 CST X-Transaction-ID: 0877e90f4b584cbe94a878d807b39f22 X-Real-From: 15330273260@189.cn X-Receive-IP: 114.242.206.180 X-MEDUSA-Status: 0 Sender: 15330273260@189.cn Message-ID: <2cf50ad0-e4fa-17a3-3e22-7fd8d4a316ed@189.cn> Date: Sat, 10 Jun 2023 01:43:39 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [Intel-gfx] [PATCH v3 4/4] PCI/VGA: introduce is_boot_device function callback to vga_client_register To: Bjorn Helgaas , Sui Jingfeng Cc: Somalapuram Amaranath , Karol Herbst , nouveau@lists.freedesktop.org, Joonas Lahtinen , dri-devel@lists.freedesktop.org, YiPeng Chai , Mario Limonciello , David Airlie , Ville Syrjala , Yi Liu , kvm@vger.kernel.org, amd-gfx@lists.freedesktop.org, Jason Gunthorpe , Ben Skeggs , linux-pci@vger.kernel.org, Andrey Grodzovsky , Kevin Tian , Lijo Lazar , Daniel Vetter , Bokun Zhang , intel-gfx@lists.freedesktop.org, Maarten Lankhorst , Maxime Ripard , loongson-kernel@lists.loongnix.cn, Alex Williamson , Abhishek Sahu , Jani Nikula , Rodrigo Vivi , Bjorn Helgaas , Tvrtko Ursulin , Yishai Hadas , Li Yi , Pan Xinhui , linux-kernel@vger.kernel.org, Thomas Zimmermann , Cornelia Huck , Alex Deucher , Christian Konig , Hawking Zhang References: <20230609164850.GA1251187@bhelgaas> Content-Language: en-US From: Sui Jingfeng <15330273260@189.cn> In-Reply-To: <20230609164850.GA1251187@bhelgaas> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 2023/6/10 00:48, Bjorn Helgaas wrote: > On Fri, Jun 09, 2023 at 10:27:39AM +0800, Sui Jingfeng wrote: >> On 2023/6/9 03:19, Bjorn Helgaas wrote: >>> On Thu, Jun 08, 2023 at 07:43:22PM +0800, Sui Jingfeng wrote: >>>> From: Sui Jingfeng >>>> >>>> The vga_is_firmware_default() function is arch-dependent, which doesn't >>>> sound right. At least, it also works on the Mips and LoongArch platforms. >>>> Tested with the drm/amdgpu and drm/radeon drivers. However, it's difficult >>>> to enumerate all arch-driver combinations. I'm wrong if there is only one >>>> exception. >>>> >>>> With the observation that device drivers typically have better knowledge >>>> about which PCI bar contains the firmware framebuffer, which could avoid >>>> the need to iterate all of the PCI BARs. >>>> >>>> But as a PCI function at pci/vgaarb.c, vga_is_firmware_default() is >>>> probably not suitable to make such an optimization for a specific device. >>>> >>>> There are PCI display controllers that don't have a dedicated VRAM bar, >>>> this function will lose its effectiveness in such a case. Luckily, the >>>> device driver can provide an accurate workaround. >>>> >>>> Therefore, this patch introduces a callback that allows the device driver >>>> to tell the VGAARB if the device is the default boot device. This patch >>>> only intends to introduce the mechanism, while the implementation is left >>>> to the device driver authors. Also honor the comment: "Clients have two >>>> callback mechanisms they can use" >>> s/bar/BAR/ (several) >>> >>> Nothing here uses the callback. I don't want to merge this until we >>> have a user. >> This is chicken and egg question. >> >> If you could help get this merge first, I will show you the first user. >> >>> I'm not sure why the device driver should know whether its device is >>> the default boot device. >> It's not that the device driver should know, >> >> but it's about that the device driver has the right to override. >> >> Device driver may have better approach to identify the default boot >> device. > The way we usually handle this is to include the new callback in the > same series as the first user of it. That has two benefits: > (1) everybody can review the whole picture and possibly suggest > different approaches, and (2) when we merge the infrastructure, > we also merge a user of it at the same time, so the whole thing can be > tested and we don't end up with unused code. OK, acceptable I will try to prepare the user code of this callback and respin the patch. I may resend it with another patch set in the future, this series already drop it, see v5[1] [1] https://patchwork.freedesktop.org/series/119134/ > Bjorn