From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 DA4E1409131; Thu, 4 Jun 2026 12:59:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780577943; cv=none; b=fBPNfsxjMo9MXpnIncNqe8dFlokT5Y0OkSLoNy9dfCQ7biVEfKTcOrb68a2mrczvWA4SIxiHdArYrbgcsbSDh10Z1rz40x68RkgLWr73/+1UJ96KGPNE6B255xTsiMgT8Im386J+10xOcJ22mD398QzqQsg4TbtqonECMbX4rRQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780577943; c=relaxed/simple; bh=ns6EOiv/DbO2oyNf7BQsADHvEVxuPqFiM2RPQ8DKZeY=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=iVLAOxYfUZTrHOyimBAVNIOpFAcm4Q0UAQRrjY3/17SmYApWc8NYQByO5Y8k1osHkRPYWHKGTCMrhc/oEviwivDxeAvvB1UJYD8vmaWO9PFwvyxOz5w46b5v4phZ36bl7xGdhtlHUvSCy7a5tTI63QTHzRIUwnvo0EKQ1St+7Ck= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BEbFpXyb; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BEbFpXyb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1F6231F00893; Thu, 4 Jun 2026 12:58:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780577942; bh=ns6EOiv/DbO2oyNf7BQsADHvEVxuPqFiM2RPQ8DKZeY=; h=From:To:Cc:Subject:In-Reply-To:References:Date; b=BEbFpXybcDnZt90rF1wHgq0+lDe5SGsffyAP9HouNZYlR/6fmN9ghOtswpIcmXhlQ GeTq8s/B32fY8atHayl/nczGINGnHSlBiSHTSZc0y6DjJZirhd5lJDUF4NjmSVvjPv /NvOUHqxu3cPrJLAzXoyk3Gm9c/4fj+ag7FZanFRg0KWZzp6aH8wYpDno/I7efHozt J/12RRLCaSuupTwxWP0eNNYFBJuaoioRwgGnZEpqtL5e4SxHL147nwFiv3qvZ2yJ1/ oTw0Zkk4uzvAcHeAL2N1BOnomgYVfWL4ZpcTFC/n7ZXV0zk8zS04q5wRRIY6rCt4PW NnNML3iCU7Tag== X-Mailer: emacs 30.2 (via feedmail 11-beta-1 I) From: Aneesh Kumar K.V To: gregkh@linuxfounation.org, linux-coco@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Catalin Marinas , Jeremy Linton , Jonathan Cameron , Lorenzo Pieralisi , Mark Rutland , Sudeep Holla , Will Deacon , Steven Price , Suzuki K Poulose Subject: Re: [PATCH v6 0/4] Switch Arm SMCCC firmware services to an SMCCC bus In-Reply-To: <20260527100233.428018-1-aneesh.kumar@kernel.org> References: <20260527100233.428018-1-aneesh.kumar@kernel.org> Date: Thu, 04 Jun 2026 18:28:54 +0530 Message-ID: Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Hi Greg, "Aneesh Kumar K.V (Arm)" writes: > As discussed here: > https://lore.kernel.org/all/20250728135216.48084-12-aneesh.kumar@kernel.org > > The earlier CCA guest support used an arm-cca-dev platform device as a pure > software anchor for the TSM class device. That platform device did not > correspond to a DT/ACPI described device, MMIO range, interrupt, or other > platform resource; it existed only to make the CCA guest driver bind and to > place the resulting TSM device in the driver model. The same pattern also > exists for smccc_trng. Creating separate platform devices for such > SMCCC-discovered features is misleading, because those features are not > independent platform devices. > > This series adds an Arm SMCCC bus for services discovered through the SMCCC > firmware interface. The bus provides SMCCC device and driver registration > helpers, name-based matching, uevent modalias generation, and a sysfs modalias > attribute. SMCCC service drivers can use MODULE_DEVICE_TABLE(arm_smccc, ...) > to emit arm_smccc: aliases, allowing userspace to autoload service > drivers when the SMCCC core registers matching firmware-service devices. > > The series then moves SMCCC TRNG and the Arm CCA guest RSI service off the > platform bus. When the SMCCC core discovers the corresponding firmware > service, it registers an arm-smccc device for that service. The hwrng > arm_smccc_trng driver and the Arm CCA guest TSM provider are converted to > SMCCC drivers that bind to those discovered devices. > > The old arm-cca-dev platform device has also been used by userspace as a Realm > guest indicator. Removing it without a replacement would leave userspace > depending on an internal driver-binding device. This series therefore adds > /sys/firmware/cca/realm_guest as a stable, architecture-provided ABI for > detecting whether the kernel is running as an Arm CCA Realm guest, and then > removes the dummy arm-cca-dev platform-device registration. > Gentle ping. Based on your feedback in [1], I reworked the series to use an SMCCC bus, with smccc-trng and arm-cca-dev represented as devices on that bus. Could you let me know whether this approach addresses your concerns? [1] https://lore.kernel.org/all/2026051451-comfort-museum-4d2a@gregkh/ -aneesh