From patchwork Thu Jul 21 04:43:52 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Airlie X-Patchwork-Id: 592445 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 73EC6C433EF for ; Thu, 21 Jul 2022 04:44:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230147AbiGUEoQ (ORCPT ); Thu, 21 Jul 2022 00:44:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39360 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229579AbiGUEoO (ORCPT ); Thu, 21 Jul 2022 00:44:14 -0400 Received: from us-smtp-delivery-44.mimecast.com (us-smtp-delivery-44.mimecast.com [205.139.111.44]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id EEB63743D1 for ; Wed, 20 Jul 2022 21:44:13 -0700 (PDT) Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-198-wCWCKbzDPBOPH_d9xnmbWw-1; Thu, 21 Jul 2022 00:44:01 -0400 X-MC-Unique: wCWCKbzDPBOPH_d9xnmbWw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 80331811E80; Thu, 21 Jul 2022 04:44:00 +0000 (UTC) Received: from dreadlord.bne.redhat.com (fdacunha.bne.redhat.com [10.64.0.157]) by smtp.corp.redhat.com (Postfix) with ESMTP id BEEA3909FF; Thu, 21 Jul 2022 04:43:55 +0000 (UTC) From: Dave Airlie To: torvalds@linux-foundation.org, Jonathan Corbet , linux-doc@vger.kernel.org, gregkh@linuxfoundation.org, Daniel Vetter , mcgrof@kernel.org Cc: linux-kernel@vger.kernel.org, dri-devel@lists.sf.net, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, alsa-devel@alsa-project.org, linux-media@vger.kernel.org, linux-block@vger.kernel.org, Dave Airlie , Rodrigo Vivi , Harry Wentland Subject: [PATCH] docs: driver-api: firmware: add driver firmware guidelines. (v3) Date: Thu, 21 Jul 2022 14:43:52 +1000 Message-Id: <20220721044352.3110507-1-airlied@gmail.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org From: Dave Airlie A recent snafu where Intel ignored upstream feedback on a firmware change, led to a late rc6 fix being required. In order to avoid this in the future we should document some expectations around linux-firmware. I was originally going to write this for drm, but it seems quite generic advice. v2: rewritten with suggestions from Thorsten Leemhuis v3: rewritten with suggestions from Mauro Acked-by: Luis Chamberlain Acked-by: Rodrigo Vivi Acked-by: Daniel Vetter Acked-by: Harry Wentland Signed-off-by: Dave Airlie --- Documentation/driver-api/firmware/core.rst | 1 + .../firmware/firmware-usage-guidelines.rst | 44 +++++++++++++++++++ 2 files changed, 45 insertions(+) create mode 100644 Documentation/driver-api/firmware/firmware-usage-guidelines.rst diff --git a/Documentation/driver-api/firmware/core.rst b/Documentation/driver-api/firmware/core.rst index 1d1688cbc078..803cd574bbd7 100644 --- a/Documentation/driver-api/firmware/core.rst +++ b/Documentation/driver-api/firmware/core.rst @@ -13,4 +13,5 @@ documents these features. direct-fs-lookup fallback-mechanisms lookup-order + firmware-usage-guidelines diff --git a/Documentation/driver-api/firmware/firmware-usage-guidelines.rst b/Documentation/driver-api/firmware/firmware-usage-guidelines.rst new file mode 100644 index 000000000000..fdcfce42c6d2 --- /dev/null +++ b/Documentation/driver-api/firmware/firmware-usage-guidelines.rst @@ -0,0 +1,44 @@ +=================== +Firmware Guidelines +=================== + +Users switching to a newer kernel should *not* have to install newer +firmware files to keep their hardware working. At the same time updated +firmware files must not cause any regressions for users of older kernel +releases. + +Drivers that use firmware from linux-firmware should follow the rules in +this guide. (Where there is limited control of the firmware, +i.e. company doesn't support Linux, firmwares sourced from misc places, +then of course these rules will not apply strictly.) + +* Firmware files shall be designed in a way that it allows checking for + firmware ABI version changes. It is recommended that firmware files be + versioned with at least a major/minor version. It is suggested that + the firmware files in linux-firmware be named with some device + specific name, and just the major version. The firmware version should + be stored in the firmware header, or as an exception, as part of the + firmware file name, in order to let the driver detact any non-ABI + fixes/changes. The firmware files in linux-firmware should be + overwritten with the newest compatible major version. Newer major + version firmware shall remain compatible with all kernels that load + that major number. + +* If the kernel support for the hardware is normally inactive, or the + hardware isn't available for public consumption, this can + be ignored, until the first kernel release that enables that hardware. + This means no major version bumps without the kernel retaining + backwards compatibility for the older major versions. Minor version + bumps should not introduce new features that newer kernels depend on + non-optionally. + +* If a security fix needs lockstep firmware and kernel fixes in order to + be successful, then all supported major versions in the linux-firmware + repo that are required by currently supported stable/LTS kernels, + should be updated with the security fix. The kernel patches should + detect if the firmware is new enough to declare if the security issue + is fixed. All communications around security fixes should point at + both the firmware and kernel fixes. If a security fix requires + deprecating old major versions, then this should only be done as a + last option, and be stated clearly in all communications. +