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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 ED5A9C433F5 for ; Mon, 27 Aug 2018 09:01:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 94646208D5 for ; Mon, 27 Aug 2018 09:01:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 94646208D5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bootlin.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727105AbeH0Mqp (ORCPT ); Mon, 27 Aug 2018 08:46:45 -0400 Received: from mail.bootlin.com ([62.4.15.54]:33715 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726785AbeH0Mqo (ORCPT ); Mon, 27 Aug 2018 08:46:44 -0400 Received: by mail.bootlin.com (Postfix, from userid 110) id 8BBFE20795; Mon, 27 Aug 2018 11:00:57 +0200 (CEST) Received: from bbrezillon (AAubervilliers-681-1-53-19.w90-88.abo.wanadoo.fr [90.88.170.19]) by mail.bootlin.com (Postfix) with ESMTPSA id C32F820789; Mon, 27 Aug 2018 11:00:56 +0200 (CEST) Date: Mon, 27 Aug 2018 11:00:55 +0200 From: Boris Brezillon To: Bartosz Golaszewski Cc: Andrew Lunn , linux-doc , Sekhar Nori , Bartosz Golaszewski , Srinivas Kandagatla , linux-i2c , Mauro Carvalho Chehab , Rob Herring , Florian Fainelli , Kevin Hilman , Richard Weinberger , Russell King , Marek Vasut , Paolo Abeni , Dan Carpenter , Grygorii Strashko , David Lechner , Arnd Bergmann , Sven Van Asbroeck , "open list:MEMORY TECHNOLOGY..." , Linux-OMAP , Linux ARM , Ivan Khoronzhuk , Greg Kroah-Hartman , Jonathan Corbet , Linux Kernel Mailing List , Lukas Wunner , Naren , netdev , Alban Bedel , Andrew Morton , Brian Norris , David Woodhouse , "David S . Miller" Subject: Re: [PATCH v2 01/29] nvmem: add support for cell lookups Message-ID: <20180827110055.122988d0@bbrezillon> In-Reply-To: References: <20180810080526.27207-1-brgl@bgdev.pl> <20180810080526.27207-2-brgl@bgdev.pl> <20180824170848.29594318@bbrezillon> <20180824152740.GD27483@lunn.ch> <20180825082722.567e8c9a@bbrezillon> X-Mailer: Claws Mail 3.15.0-dirty (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 27 Aug 2018 10:56:29 +0200 Bartosz Golaszewski wrote: > 2018-08-25 8:27 GMT+02:00 Boris Brezillon : > > On Fri, 24 Aug 2018 17:27:40 +0200 > > Andrew Lunn wrote: > > > >> On Fri, Aug 24, 2018 at 05:08:48PM +0200, Boris Brezillon wrote: > >> > Hi Bartosz, > >> > > >> > On Fri, 10 Aug 2018 10:04:58 +0200 > >> > Bartosz Golaszewski wrote: > >> > > >> > > +struct nvmem_cell_lookup { > >> > > + struct nvmem_cell_info info; > >> > > + struct list_head list; > >> > > + const char *nvmem_name; > >> > > +}; > >> > > >> > Hm, maybe I don't get it right, but this looks suspicious. Usually the > >> > consumer lookup table is here to attach device specific names to > >> > external resources. > >> > > >> > So what I'd expect here is: > >> > > >> > struct nvmem_cell_lookup { > >> > /* The nvmem device name. */ > >> > const char *nvmem_name; > >> > > >> > /* The nvmem cell name */ > >> > const char *nvmem_cell_name; > >> > > >> > /* > >> > * The local resource name. Basically what you have in the > >> > * nvmem-cell-names prop. > >> > */ > >> > const char *conid; > >> > }; > >> > > >> > struct nvmem_cell_lookup_table { > >> > struct list_head list; > >> > > >> > /* ID of the consumer device. */ > >> > const char *devid; > >> > > >> > /* Array of cell lookup entries. */ > >> > unsigned int ncells; > >> > const struct nvmem_cell_lookup *cells; > >> > }; > >> > > >> > Looks like your nvmem_cell_lookup is more something used to attach cells > >> > to an nvmem device, which is NVMEM provider's responsibility not the > >> > consumer one. > >> > >> Hi Boris > >> > >> There are cases where there is not a clear providier/consumer split. I > >> have an x86 platform, with a few at24 EEPROMs on it. It uses an off > >> the shelf Komtron module, placed on a custom carrier board. One of the > >> EEPROMs contains the hardware variant information. Once i know the > >> variant, i need to instantiate other I2C, SPI, MDIO devices, all using > >> platform devices, since this is x86, no DT available. > >> > >> So the first thing my x86 platform device does is instantiate the > >> first i2c device for the AT24. Once the EEPROM pops into existence, i > >> need to add nvmem cells onto it. So at that point, the x86 platform > >> driver is playing the provider role. Once the cells are added, i can > >> then use nvmem consumer interfaces to get the contents of the cell, > >> run a checksum, and instantiate the other devices. > >> > >> I wish the embedded world was all DT, but the reality is that it is > >> not :-( > > > > Actually, I'm not questioning the need for this feature (being able to > > attach NVMEM cells to an NVMEM device on a platform that does not use > > DT). What I'm saying is that this functionality is provider related, > > not consumer related. Also, I wonder if defining such NVMEM cells > > shouldn't go through the provider driver instead of being passed > > directly to the NVMEM layer, because nvmem_config already have a fields > > to pass cells at registration time, plus, the name of the NVMEM cell > > device is sometimes created dynamically and can be hard to guess at > > platform_device registration time. > > > > In my use case the provider is at24 EEPROM driver. This is where the > nvmem_config lives but I can't image a correct and clean way of > passing this cell config to the driver from board files without using > new ugly fields in platform_data which this very series is trying to > remove. This is why this cell config should live in machine code. Okay. > > > I also think non-DT consumers will need a way to reference exiting > > NVMEM cells, but this consumer-oriented nvmem cell lookup table should > > look like the gpio or pwm lookup table (basically what I proposed in my > > previous email). > > How about introducing two new interfaces to nvmem: one for defining > nvmem cells from machine code and the second for connecting these > cells with devices? Yes, that's basically what I was suggesting: move what you've done in nvmem-provider.h (maybe rename some of the structs to make it clear that this is about defining cells not referencing existing ones), and add a new consumer interface (based on what other subsystems do) in nvmem-consumer.h. This way you have both things clearly separated, and if a driver is both a consumer and a provider you'll just have to include both headers. Regards, Boris