Received: by 2002:a25:683:0:0:0:0:0 with SMTP id 125csp771820ybg; Wed, 10 Jun 2020 13:18:32 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzNKI5nqbDoflfZfXIiGkSXCkjm88+4WwgeTuONVIs4E9l6reLQ1SWO3WU4LM9UixRHv/lq X-Received: by 2002:a50:cfc4:: with SMTP id i4mr3927853edk.252.1591820312321; Wed, 10 Jun 2020 13:18:32 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1591820312; cv=none; d=google.com; s=arc-20160816; b=EVDuO62ct3OvDU4P5W6WZGQLh90rtPhh9Dk2y7IsRnuHdaQswe9F4wXcQZg67bRND+ KxIt3ywB6cpH2giFe1K4Y7Pd0Z5SnH4PM3Vdbm7oTLNWa0v6feODUWKyOo8uxeVJI+sQ cm6zDtgDVIoNTWZnQgSCkc/4qpuk2QZ7bttuoUlk9Dy2qgh1+FRYeCwR/RelM9AeRZw9 VxS3ytbkY9rczT+j25Mw7ubDV+R8sVJ18t8zrXsc75OEhn5W5jDpTf9NAtiLm5Et1APj 8BTFM9WaYPgWNWbTI8ebIbBRZvKpOxZTcfnBljAqPwDuEaw44nqOiTTur59xxH6uUyNR rr+A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:in-reply-to:content-transfer-encoding :content-disposition:mime-version:references:message-id:subject:cc :to:from:date:dkim-signature; bh=/+J5oO5OnfDiIOVOhIHmtbQvypR4NOyguvZ+vS+VBRA=; b=RtSn4ZSeIhY6bQyuhIRq/h7bBjMakYeioIfbh/dCrK6ahJ0ENE4PpGoLDc7qHKh9Cd 8TdTegGW2Pm+mxeD3Dn+Hq+dbGRs4mf5VXJenbHWBuefdVqvA3YDoMNQsXvmVwgmGOoo 6dgOAeYd/3d80VdYq7Hx0tiwXpU5jvS6W1oyIhzZ5bble40GInpzcNu5paFnuoea6Ydh D9L6ikGCikr57o2LtxECvkSwDLBHRnVF+plp+Hggt59cjk4XXctmsTp7vV5TOHRQEA8A Bp86zCRbQldViUEE9oliucH/4WA3vsUuPgpkR0Lkjghmmc/tifRIGyCalCW2tVGBJvhA n9rw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=DV34bec3; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id w19si350684edt.402.2020.06.10.13.18.08; Wed, 10 Jun 2020 13:18:32 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=DV34bec3; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728962AbgFJSbA (ORCPT + 99 others); Wed, 10 Jun 2020 14:31:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44606 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728859AbgFJSa7 (ORCPT ); Wed, 10 Jun 2020 14:30:59 -0400 Received: from mail-wr1-x441.google.com (mail-wr1-x441.google.com [IPv6:2a00:1450:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8487AC08C5C3 for ; Wed, 10 Jun 2020 11:30:58 -0700 (PDT) Received: by mail-wr1-x441.google.com with SMTP id e1so3428205wrt.5 for ; Wed, 10 Jun 2020 11:30:58 -0700 (PDT) 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=/+J5oO5OnfDiIOVOhIHmtbQvypR4NOyguvZ+vS+VBRA=; b=DV34bec3kn8ups3mo1KcqY/YeluhEBHJfMnEoE9K8u+na1nJ1DGGsyc4jU+glucolT TUviM5dxviwZLPuM0g8+vQXe6cH2pxFxUWwU93dsLznmfLILTgw0LIRBUGyUiEr5eR3C YVHYT4otqvUKNG5g6IBlf3xE5gnzBzFj8GQusuekh3De1azhWfnqZ9zrNkArwxjoeSDN OrOIMECTmg9RCEjAQB7ALp90Ij1RGNwkk5LC/8K25KqHj43cQrS4VRgqmzzK2AP4yrmE cR6KgKL7WPcVlg8QndhCyIa1+G17DLQVODULBk72RsyfmyYYRSqETFm9e19h9C2G/EmO VhdA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=/+J5oO5OnfDiIOVOhIHmtbQvypR4NOyguvZ+vS+VBRA=; b=On0N+KY3AOqgyrhdB28LoBciTUk2GBzW0Il5197Hi3ft4pETbpgJyFzIdn2V23bPl0 RoFottjO12w9mkz6WgPlJpQzOOICHt27J58lZ6gUL6sK+3+9MiZiRUlSn7XbMV//zZjm jlhV2RMUHLgTUn01ad/vO/qPlzj2MJXTD/znKbUcGwnhSzgfyczyIF622In0nrdkanzL bBFdoOwSZjapqMN0HHF4QN1yS8FXLmrwELK1TeVKHImOVq3jGywJQ/Eqqvb9OztHOdXV R7eSSHFpFdA93VdLSUQP2AeYYDoa32fCiAdT3voaP8jELdBTq1tPG0pOGM3C3ZN4b5Sa enEQ== X-Gm-Message-State: AOAM531oiSqI1xDhCusZKhFgV9bUg+KKEl49wu7Z9gR+RbcoNF7NBEWq HNuPSkb5IOrU/ZZbTEgMOt2CaA== X-Received: by 2002:adf:c98a:: with SMTP id f10mr5095428wrh.329.1591813856649; Wed, 10 Jun 2020 11:30:56 -0700 (PDT) Received: from dell ([2.27.167.101]) by smtp.gmail.com with ESMTPSA id a15sm878966wra.86.2020.06.10.11.30.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Jun 2020 11:30:55 -0700 (PDT) Date: Wed, 10 Jun 2020 19:30:53 +0100 From: Lee Jones To: Michael Walle Cc: Andy Shevchenko , Ranjani Sridharan , david.m.ertman@intel.com, shiraz.saleem@intel.com, Rob Herring , Mark Brown , "open list:GPIO SUBSYSTEM" , devicetree , Linux Kernel Mailing List , linux-hwmon@vger.kernel.org, linux-pwm@vger.kernel.org, linux-watchdog@vger.kernel.org, linux-arm Mailing List , Linus Walleij , Bartosz Golaszewski , Jean Delvare , Guenter Roeck , Thierry Reding , Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Wim Van Sebroeck , Shawn Guo , Li Yang , Thomas Gleixner , Jason Cooper , Marc Zyngier , Greg Kroah-Hartman , Andy Shevchenko Subject: Re: [PATCH v4 02/11] mfd: Add support for Kontron sl28cpld management controller Message-ID: <20200610183053.GV4106@dell> References: <20200609064735.GH4106@dell> <32287ac0488f7cbd5a7d1259c284e554@walle.cc> <20200609151941.GM4106@dell> <95e6ec9bbdf6af7a9ff9c31786f743f2@walle.cc> <20200609194505.GQ4106@dell> <3a6931248f0efcaf8efbb5425a9bd833@walle.cc> <20200610071940.GS4106@dell> <20200610075615.GT4106@dell> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 10 Jun 2020, Michael Walle wrote: > Am 2020-06-10 09:56, schrieb Lee Jones: > > On Wed, 10 Jun 2020, Michael Walle wrote: > > > > > Am 2020-06-10 09:19, schrieb Lee Jones: > > > > On Wed, 10 Jun 2020, Michael Walle wrote: > > > > > Am 2020-06-09 21:45, schrieb Lee Jones: > > > > > > On Tue, 09 Jun 2020, Michael Walle wrote: > > > > > > > > We do not need a 'simple-regmap' solution for your use-case. > > > > > > > > > > > > > > > > Since your device's registers are segregated, just split up the > > > > > > > > register map and allocate each sub-device with it's own slice. > > > > > > > > > > > > > > I don't get it, could you make a device tree example for my > > > > > > > use-case? (see also above) > > > > > > > > > > > > &i2cbus { > > > > > > mfd-device@10 { > > > > > > compatible = "simple-mfd"; > > > > > > reg = <10>; > > > > > > > > > > > > sub-device@10 { > > > > > > compatible = "vendor,sub-device"; > > > > > > reg = <10>; > > > > > > }; > > > > > > }; > > > > > > > > > > > > The Regmap config would be present in each of the child devices. > > > > > > > > > > > > Each child device would call devm_regmap_init_i2c() in .probe(). > > > > > > > > > > Ah, I see. If I'm not wrong, this still means to create an i2c > > > > > device driver with the name "simple-mfd". > > > > > > > > Yes, it does. > > > > > > > > > Besides that, I don't like this, because: > > > > > - Rob already expressed its concerns with "simple-mfd" and so on. > > > > > > > > Where did this take place? I'd like to read up on this. > > > > > > In this thread: > > > https://lore.kernel.org/linux-devicetree/20200604211039.12689-1-michael@walle.cc/T/#m16fdba5962069e7cd4aa817582ee358c9fe2ecbf > > > > > > > > > > > > - you need to duplicate the config in each sub device > > > > > > > > You can have a share a single config. > > > > > > > > > - which also means you are restricting the sub devices to be > > > > > i2c only (unless you implement and duplicate other regmap configs, > > > > > too). For this driver, SPI and MMIO may be viable options. > > > > > > > > You could also have a shared implementation to choose between different > > > > busses. > > > > > > Then what is the difference between to have this shared config in the > > > parent driver only and use the functions which are already there, i.e. > > > dev_get_regmap(parent). But see, below, I'll wait with what you're > > > coming up. > > > > The difference is the omission of an otherwise pointless/superfluous > > driver. Actually, it's the difference between the omission of 10 > > pointless drivers! > > If you want to omit anything generic in the device tree - and as far as > I understand it - that should be the way to go, the specific compatible > string of the parent device has to go somewhere. Thus I'd appreciate > a consolidated (MFD) driver which holds all these, as you say it > pointless drivers. > Because IMHO they are not pointless, rather they are > the actual drivers for the MFD. Its sub nodes are just an implementation > detail to be able to use the OF bindings > (like your clock example or > a phandle to a PWM controller). Just because it is almost nothing there > except the regmap instantiation doesn't mean it is not a valid MFD driver. A valid MFD driver is whatever we (the Linux community at large) define it to be. An MFD is not a real thing. We made it up. It's MFD which is the implementation detail, not the child devices. If a driver a) does very little, and b) the very little it does do can be resolved in a different way, is not a valid driver. It's a waste of disk space. > And there is also additional stuff, like clock enable, version checks, etc. As more functionality is added *then* we can justify a driver. -- Lee Jones [李琼斯] Senior Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog