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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 98E83C433FE for ; Mon, 10 Jan 2022 12:23:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245415AbiAJMXW (ORCPT ); Mon, 10 Jan 2022 07:23:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33070 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245394AbiAJMXO (ORCPT ); Mon, 10 Jan 2022 07:23:14 -0500 Received: from mail-wr1-x431.google.com (mail-wr1-x431.google.com [IPv6:2a00:1450:4864:20::431]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4B33C061751 for ; Mon, 10 Jan 2022 04:23:13 -0800 (PST) Received: by mail-wr1-x431.google.com with SMTP id r9so24652194wrg.0 for ; Mon, 10 Jan 2022 04:23:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=d5pQe12aMTp9K2Ar029wPLMoAM2l+tag/tJuNAihSfA=; b=oJPzZWiJGiiJbT4/DpmWXxwLQYl6V3un3f2VMq9gR7xu1Vg0i7bZ927q0i6k6AQopH EMyuitOKXW8UrzPrA8eOw7VIwHiup4VsiSBK70Fwh3ZHQOw8z80zEoQuv/4CO+GM9ivz F5QUJ+ddCeY/O2IGHQoaAHfFjZBPVjvkv+z5R1r8GVyPWIRO/0eMm5lWFMJ9u0SODO/G MdBs5h8FelfgOYX3f78MFfDQiSxzbfqga00uHApimjp9PagVhvMXJoFmnNYqNKov7brQ vTMyqbYIDiV5KSYQLZHE20N7CHzkl+83RKoT9KdBiD7amP2upvF6OjdjXJB6L3Rolsqe gmUA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=d5pQe12aMTp9K2Ar029wPLMoAM2l+tag/tJuNAihSfA=; b=QN+UmTkzD3U2d7dutQbOY9inx1vKkqpScVgmOMnVDc7Mvd5d1ZTzDEJdsGAcKuZltl +Mu8bf5xJRapocXeFG6WzP4pe/Hb9zA0Qt8COgRLSUsquLFnEB4ZXM14/k0PX9jHggGI H6S3JHbuhp0rFuPQqkJIlGd1esKvXAgyR1SXROdXbPdx7hU27Mkhmavw7E2OUFxi/t1v v3KJsOajBwDClUJqh2fm/9X3xZRddHEDuCqZkrO97JEKlXUfbAmhy1amiolARWydX2AG obTmRZwq5jWamR6fgDm5AqtiusBNbTBC/M2Rz/GqTs2V/FqzxcfNmeuZdDUjQuk1QqXa 5SVQ== X-Gm-Message-State: AOAM530h+Y7ksDYoQpJ8S7bsyXm8Z08UfAU6HOm+Cg9yRMPevpX7gcEF qdxpDvcynGnOoRMgwv6XPxkbfw== X-Google-Smtp-Source: ABdhPJxJTGBqADrh2dO8M5zq/V0efObTWO7ybtVGTQGANdUuw72l8ka3sOvJLzv6aUoWNXVdmQ1BEQ== X-Received: by 2002:adf:e2cc:: with SMTP id d12mr17686855wrj.107.1641817392300; Mon, 10 Jan 2022 04:23:12 -0800 (PST) Received: from google.com ([31.124.24.179]) by smtp.gmail.com with ESMTPSA id l4sm6533168wrm.62.2022.01.10.04.23.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Jan 2022 04:23:11 -0800 (PST) Date: Mon, 10 Jan 2022 12:23:09 +0000 From: Lee Jones To: Colin Foster Cc: linux-gpio@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Walleij , Russell King , Heiner Kallweit , Jakub Kicinski , "David S. Miller" , Florian Fainelli , Vivien Didelot , Andrew Lunn , UNGLinuxDriver@microchip.com, Alexandre Belloni , Claudiu Manoil , Vladimir Oltean Subject: Re: [RFC v5 net-next 08/13] mfd: add interface to check whether a device is mfd Message-ID: References: <20211218214954.109755-1-colin.foster@in-advantage.com> <20211218214954.109755-9-colin.foster@in-advantage.com> <20211230020443.GB1347882@euler> <20211230201253.GA1484230@euler> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20211230201253.GA1484230@euler> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 30 Dec 2021, Colin Foster wrote: > On Thu, Dec 30, 2021 at 01:43:53PM +0000, Lee Jones wrote: > > On Wed, 29 Dec 2021, Colin Foster wrote: > > > > > On Wed, Dec 29, 2021 at 03:25:55PM +0000, Lee Jones wrote: > > > > On Sat, 18 Dec 2021, Colin Foster wrote: > > > > > > > > > Some drivers will need to create regmaps differently based on whether they > > > > > are a child of an MFD or a standalone device. An example of this would be > > > > > if a regmap were directly memory-mapped or an external bus. In the > > > > > memory-mapped case a call to devm_regmap_init_mmio would return the correct > > > > > regmap. In the case of an MFD, the regmap would need to be requested from > > > > > the parent device. > > > > > > > > > > This addition allows the driver to correctly reason about these scenarios. > > > > > > > > > > Signed-off-by: Colin Foster > > > > > --- > > > > > drivers/mfd/mfd-core.c | 5 +++++ > > > > > include/linux/mfd/core.h | 10 ++++++++++ > > > > > 2 files changed, 15 insertions(+) > > > > > > > > > > diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c > > > > > index 684a011a6396..905f508a31b4 100644 > > > > > --- a/drivers/mfd/mfd-core.c > > > > > +++ b/drivers/mfd/mfd-core.c > > > > > @@ -33,6 +33,11 @@ static struct device_type mfd_dev_type = { > > > > > .name = "mfd_device", > > > > > }; > > > > > > > > > > +int device_is_mfd(struct platform_device *pdev) > > > > > +{ > > > > > + return (!strcmp(pdev->dev.type->name, mfd_dev_type.name)); > > > > > +} > > > > > + > > > > > > > > Why is this device different to any other that has ever been > > > > mainlined? > > > > > > Hi Lee, > > > > > > First, let me apologize for not responding to your response from the > > > related RFC from earlier this month. It had been blocked by my spam > > > filter and I had not seen it until just now. I'll have to check that > > > more diligently now. > > > > > > Moving on... > > > > > > That's a question I keep asking myself. Either there's something I'm > > > missing, or there's something new I'm doing. > > > > > > This is taking existing drivers that work via MMIO regmaps and making > > > them interface-independent. As Vladimir pointed out here: > > > https://lore.kernel.org/all/20211204022037.dkipkk42qet4u7go@skbuf/T/ > > > device_is_mfd could be dropped in lieu of an mfd-specific probe > > > function. > > > > > > If there's something I'm missing, please let me know. But it feels like > > > devm_get_regmap_from_resource at the end of the day would be the best > > > solution to the design, and that doesn't exist. And implementing > > > something like that is a task that I feel I'm not capable of tackling at > > > this time. > > > > I'm really not a fan of leaking any MFD API outside of drivers/mfd. > > MFD isn't a tangible thing. It's a Linuxiusm, something we made up, a > > figment of your imagination. > > > > What happens if you were to all dev_get_regmap() in the non-MFD case > > or when you call devm_regmap_init_mmio() when the driver was > > registered via the MFD framework? > > I'd imagine dev_get_regmap in a non-MFD case would be the same as > dev_get_and_ioremap_resource() followed by devm_regmap_init_mmio(). > > In the MFD case it would possibly request the regmap from the parent, > which could reason about how to create the regmap. As you understand, > this is exactly the behavior I created in this patch set. I did it by > way of ocelot_get_regmap_from_resource, and admit it isn't the best way. > But it certainly seems there isn't an existing method that I'm missing. > > I'm coming from a pretty narrow field of view, but believe my use-case > is a valid one. If that is true, and there isn't another design I should > use... this is the opportunity to create it. Implementing > ocelot_get_regmap_from_resource is a way to achieve my needs without > affecting anyone else. > > Going one step further and implementing mfd_get_regmap_from_parent (or > similar) would creep into the design of MFD. I don't know enough about > MFD and the users to suggest this. I wouldn't want to start venturing > down that path without blessing from the community. And this would > indirectly affect every MFD driver. > > Going all in and implementing device_get_regmap_from_resource... I don't > know that I'd be comfortable even starting down that path knowing that > it would affect every device. Perhaps it would have to utilize something > like IORESOURCE_REG that seems to only get utilized in a handful of > files: > https://elixir.bootlin.com/linux/v5.16-rc7/C/ident/IORESOURCE_REG Let's speak to Mark and see if he can provide any insight. -- Lee Jones [李琼斯] Principal Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog