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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 E3D92CD4F25 for ; Thu, 14 May 2026 10:52:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:MIME-Version: Message-ID:Date:References:In-Reply-To:Subject:Cc:To:From:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=f6YNQDiAk/xlVO0n8LOtKzUmpF01ZP10NXjIieKLms0=; b=kJvZ+UTS27QjCx+zusAC30nHOS st6PJ2FlNexM6B94v/lTYKZpW/v37Q9TeVbaFRBtK1Y3q5H+6BpB9jppLl9l4D0YCWje7YCBXrAXY XYC6ASBR2XXBNngT4WCs63mD3+tt3bhHnKTWyEreIPEM5iGB4BNze/zp0UW3dBVw8TZamdb6xJywK qXbFvO2lqdawFa7pzqcsCL9w6BRWpkCXNQmZm9qj9VjyApTG5Pt1dRlKUn6fF/Lj3eTHTdSvpVCyl 3NPyxRIBdIWO5kNnWFO1ESUzUEiQmiy3rQcW1RcioLJeL4OlmJQpC7Xe84aRhIRI9TiLEK0dH9Mzr IdC4LFhw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wNTfc-00000005FA5-2uyQ; Thu, 14 May 2026 10:52:00 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wNTfa-00000005F9N-0WmS for linux-arm-kernel@lists.infradead.org; Thu, 14 May 2026 10:51:59 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id D655C438B8; Thu, 14 May 2026 10:51:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 114D4C2BCB3; Thu, 14 May 2026 10:51:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778755916; bh=NdIUfducvTRfNv9EYak+8ec9D63cIOd0Q93R/5kYsIM=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=TZGxBDkPMRNBmNhF9URVkpubYH9ZVQym8A3/b6mCW61gCl35FjejmAg5Nkv6Wbesg 9cmY4U7pCPnrbZL00Z12bH+ewTJb9/cFganuk7XvB1fUWu8rHs8QiOhEPwJ/S3sD1J EtxFChOpUSfwkLSY+Wr+A9eIYPR4APzdb80ivSay/AYG4yQQQIeQWFvC/8rm3p04J6 u5nVcJhSq0yaTi/3eVimpctCx3HHKDKC8A7us5rTjB76ZWOwuwwMfhFsWkaiHM2cFI /nL/XRo2kj6Ujd6NTPE+y4smsYdL5sRaZqCA9yG2i0baQjIe3lXqw52KSR9DUQr5VI Sg2yPIUvbctJg== X-Mailer: emacs 30.2 (via feedmail 11-beta-1 I) From: Aneesh Kumar K.V To: Greg KH Cc: linux-coco@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Catalin Marinas , Jeremy Linton , Jonathan Cameron , Lorenzo Pieralisi , Mark Rutland , Sudeep Holla , Will Deacon , Steven Price , Suzuki K Poulose Subject: Re: [PATCH v5 0/3] Switch Arm CCA to use an auxiliary device instead of a platform device In-Reply-To: <2026051453-batting-delighted-0a57@gregkh> References: <20260514094030.42495-1-aneesh.kumar@kernel.org> <2026051453-batting-delighted-0a57@gregkh> Date: Thu, 14 May 2026 16:21:48 +0530 Message-ID: MIME-Version: 1.0 Content-Type: text/plain X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260514_035158_187833_A61BD4DE X-CRM114-Status: GOOD ( 14.42 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Greg KH writes: > On Thu, May 14, 2026 at 03:10:27PM +0530, Aneesh Kumar K.V (Arm) wrote: >> As discussed here: >> https://lore.kernel.org/all/20250728135216.48084-12-aneesh.kumar@kernel.org >> >> The general feedback was that a platform device should not be used when >> there is no underlying platform resource to represent. The existing CCA >> support uses a platform device solely to anchor the TSM interface in the >> device hierarchy, which is not an appropriate use of a platform device. >> Use an auxiliary device instead to track CCA support. > > Why an aux device? If this has no platform resources, please use the > faux bus support instead, that is what it is there for. aux devices are > used when you are sharing a real resource among different "child" > drivers, and need some way to coordinate that sharing. If you have no > resources, there's nothing to share, so no need for the complexity that > aux gives you, just use faux instead. > We did discuss between faux an auxiliary devices early here https://lore.kernel.org/all/20251010135922.GC3833649@ziepe.ca To summarize auxiliary device was choosen so that we can do module autoloading. -aneesh