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 X-Spam-Level: X-Spam-Status: No, score=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E104DC433E7 for ; Fri, 16 Oct 2020 15:27:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 836B820874 for ; Fri, 16 Oct 2020 15:27:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2410050AbgJPP1B (ORCPT ); Fri, 16 Oct 2020 11:27:01 -0400 Received: from mx2.suse.de ([195.135.220.15]:55536 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2410005AbgJPP1A (ORCPT ); Fri, 16 Oct 2020 11:27:00 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 9C5F2AD87; Fri, 16 Oct 2020 15:26:58 +0000 (UTC) Message-ID: <0f0b7021e85a832afd42c6f9016158d6d8b0b28b.camel@suse.de> Subject: Re: [RFC] of/platform: Create device link between simple-mfd and its children From: Nicolas Saenz Julienne To: Rob Herring Cc: Greg Kroah-Hartman , "Wysocki, Rafael J" , Frank Rowand , Florian Fainelli , "moderated list:BROADCOM BCM2835 ARM ARCHITECTURE" , Saravana Kannan , Uwe =?ISO-8859-1?Q?Kleine-K=F6nig?= , devicetree@vger.kernel.org, "linux-kernel@vger.kernel.org" Date: Fri, 16 Oct 2020 17:26:56 +0200 In-Reply-To: References: <20201015114346.15743-1-nsaenzjulienne@suse.de> Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-qL4wvvXdx8WWS17CadgZ" User-Agent: Evolution 3.36.5 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org --=-qL4wvvXdx8WWS17CadgZ Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2020-10-16 at 09:38 -0500, Rob Herring wrote: > On Thu, Oct 15, 2020 at 6:43 AM Nicolas Saenz Julienne > wrote: > > 'simple-mfd' usage implies there might be some kind of resource sharing > > between the parent device and its children. >=20 > It does? No! The reason behind simple-mfd was specifically because > there was no parent driver or dependency on the parent. No doubt > simple-mfd has been abused. Fair enough, so we're doing things wrong. Just for the record, I'm looking = at RPi=C2=B4s firmware interface: firmware: firmware { compatible =3D "raspberrypi,bcm2835-firmware", "simple-mfd"; #address-cells =3D <1>; #size-cells =3D <1>; mboxes =3D <&mailbox>; firmware_clocks: clocks { compatible =3D "raspberrypi,firmware-clocks"; #clock-cells =3D <1>; }; reset: reset { compatible =3D "raspberrypi,firmware-reset"; #reset-cells =3D <1>; }; [...] }; Note that "raspberrypi,bcm2835-firmware" has a driver, it's not just a placeholder. Consumer drivers get a handle to RPi's firmware interface thro= ugh the supplier's API, rpi_firmware_get(). The handle to firmware becomes meaningless if it is unbinded, which I want to protect myself against. A simpler solution would be to manually create a device link between both devices ("raspberrypi,bcm2835-firmware" and "raspberrypi,firmware-clocks" f= or example) upon calling rpi_firmware_get(). But I wanted to try addressing th= e problem in a generic way first. Regards, Nicolas --=-qL4wvvXdx8WWS17CadgZ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEErOkkGDHCg2EbPcGjlfZmHno8x/4FAl+Ju8AACgkQlfZmHno8 x/5rNgf/RWzw8B+m3lZjCQJdOUIVBcSgEtXTgg+1Rw64UrNVIYeCYwRa8GbiXN6Y KzbRjnNiAIFLworJ8rpWKfKY52/Y39CJhgbXem0tM9BWJE7gLRZA8f+B0GfvXvzz /bAFMkcywkakmPssQ94zslmWhgiE3zoYQD1sSVesYBV/0cqt/2TXt8wXsdyybzbD zMLs+vkCHhQIVaYNmmB10wLmiBo9g7PMFRD9panuRsaQ1Yyrk+NvgPcOCYYtyRxS NUBmVHMcbtYv+NvxGatfp8q5kyhTUeIubYmNHXgaovlo71Rg2HCWeWZkaj5TkX7s 6n7yNJPNKEE+DcmOcwM61NaI9aYurA== =2J8u -----END PGP SIGNATURE----- --=-qL4wvvXdx8WWS17CadgZ--