From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AF6432D0629; Fri, 10 Oct 2025 12:38:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760099933; cv=none; b=LwqSOnXCJf6gRmXbheyndDKaShbZBwcAZpjydESEPlEGqWpW+D26zVnHpX5nPJ3GFfOZYRaTErRvKDOTIafFJUgB3bfXYUVwvfX4Shvq+IoJpZyebEd2/ojGgkJTCr7rRb0mukwnz2zsxSehCXT70de0I7tx1ENiBbHffXSC16w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760099933; c=relaxed/simple; bh=p2dq1+BYCl83wtRQDI4S8QRU072WIE+qdJpzYKgqGwk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=P5TOJ/IekRUMTqfFwNJl4edVWp0LCd/8xdN7QzpDDOFZo+sgAg3KrHYWfQPcfFQE67JGeYTBkSkgcJSf03RZzxA8g53LloLmGh6s2UHqlZMhBYqpjgKTnxnBCqrmZwhc+MPnAeLZged0gT7EHGshTTEwI3o9W/2yTVAgcee19XY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gCxelIpC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="gCxelIpC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 87526C4CEF1; Fri, 10 Oct 2025 12:38:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1760099933; bh=p2dq1+BYCl83wtRQDI4S8QRU072WIE+qdJpzYKgqGwk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gCxelIpCywnl2nZ+0zzEYviCt/IR7PSgK9ywEfdoWQn+oAPWP7F11LRUhgwqcpVge VRUUfQbpTeDkgpT6ATNWtNlJNzpyVp3Ok6k/i3dDGVy/2vxfxa+aX2gebckUC0W++P daAx7QgJQ2VIKINmVs97v+NZSTJ9hvGWv5Wb1mjk= Date: Fri, 10 Oct 2025 14:38:50 +0200 From: Greg KH To: Jeremy Linton Cc: Jonathan Cameron , "Aneesh Kumar K.V" , Jason Gunthorpe , Dan Williams , linux-coco@lists.linux.dev, kvmarm@lists.linux.dev, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, aik@amd.com, lukas@wunner.de, Samuel Ortiz , Xu Yilun , Suzuki K Poulose , Steven Price , Catalin Marinas , Marc Zyngier , Will Deacon , Oliver Upton Subject: Re: [RFC PATCH v1 11/38] KVM: arm64: CCA: register host tsm platform device Message-ID: <2025101020-tiara-procreate-e56f@gregkh> References: <20250728135216.48084-1-aneesh.kumar@kernel.org> <20250728135216.48084-12-aneesh.kumar@kernel.org> <20250729181045.0000100b@huawei.com> <20250729231948.GJ26511@ziepe.ca> <20250730113827.000032b8@huawei.com> <20250730132333.00006fbf@huawei.com> <2025073035-bulginess-rematch-b92e@gregkh> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Oct 10, 2025 at 07:10:58AM -0500, Jeremy Linton wrote: > Hi, > > > On 7/30/25 8:07 AM, Greg KH wrote: > > On Wed, Jul 30, 2025 at 01:23:33PM +0100, Jonathan Cameron wrote: > > > On Wed, 30 Jul 2025 11:38:27 +0100 > > > Jonathan Cameron wrote: > > > > > > > On Wed, 30 Jul 2025 14:12:26 +0530 > > > > "Aneesh Kumar K.V" wrote: > > > > > > > > > Jason Gunthorpe writes: > > > > > > On Tue, Jul 29, 2025 at 06:10:45PM +0100, Jonathan Cameron wrote: > > > > > > > > +static struct platform_device cca_host_dev = { > > > > > > > Hmm. Greg is getting increasingly (and correctly in my view) grumpy with > > > > > > > platform devices being registered with no underlying resources etc as glue > > > > > > > layers. Maybe some of that will come later. > > > > > > > > > > > > Is faux_device a better choice? I admit to not knowing entirely what > > > > > > it is for.. > > > > > > > > I'll go with a cautious yes to faux_device. This case of a glue device > > > > with no resources and no reason to be on a particular bus was definitely > > > > the intent but I'm not 100% sure without trying it that we don't run > > > > into any problems. > > > > > > > > Not that many examples yet, but cpuidle-psci.c looks like a vaguely similar > > > > case to this one. > > > > > > > > All it really does is move the location of the device and > > > > smash together the device registration with probe/remove. > > > > That means the device disappears if probe() fails, which is cleaner > > > > in many ways than leaving a pointless stub behind. > > > > > > > > Maybe it isn't appropriate it if is actually useful to rmmod/modprobe the > > > > driver. > > > > > > > > +CC Greg on basis I may have wrong end of the stick ;) > > > This time with at least one less typo in Greg's email address. > > > > Yes, use faux_device if you need/want a struct device to represent > > something in the tree and it does NOT have any real platform resources > > behind it. That's explicitly what it was designed for. > > Right, but this code is intended to trigger the kmod/userspace module > loader. Why? > AFAIK, the faux device is currently missing a faux_device_id in > mod_devicetable, alias matching logic in file2alias, and probably a few > other things which keeps it from performing this function. How would a faux device ever expect to get auto-loaded? That's not what is supposed to be happening here at all. If you have real hardware backing something, then use the real driver type. that is NOT a faux driver, which is, as the name says, for "fake" devices that you wish to add to the device/driver tree. thanks, greg k-h