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 2AF88C77B7A for ; Mon, 29 May 2023 13:43:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229893AbjE2Nn6 (ORCPT ); Mon, 29 May 2023 09:43:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58682 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229707AbjE2Nn4 (ORCPT ); Mon, 29 May 2023 09:43:56 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BDEFBAB for ; Mon, 29 May 2023 06:43:54 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 5A7AE6145E for ; Mon, 29 May 2023 13:43:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 61EF7C433D2; Mon, 29 May 2023 13:43:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1685367833; bh=unFL8pUzxL+774Yi/I3RGjS6kRnSX5niPyJgnZ0PEpE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=xOguH66PsGL+MvO7nzB8s9wcjddxHxbTMGkhaowPkgkmHMrSCB1NIVKB8a63Nvay+ ruaunESyNzbOXUyI0m+k1/p5kmF61XX8HiCtHV7gUECCG3lFvdCbmor6dTL1aqLwUs /mSDOIA7KgpStGWjOdQwwbGf4uBKSsKV7c2f7Y6Y= Date: Mon, 29 May 2023 14:43:51 +0100 From: Greg Kroah-Hartman To: Miquel Raynal Cc: Srinivas Kandagatla , Luka Perkov , Robert Marko , Thomas Petazzoni , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] nvmem: core: Expose cells through sysfs Message-ID: <2023052941-untoasted-alone-d2c5@gregkh> References: <20230523100239.307574-1-miquel.raynal@bootlin.com> <20230523100239.307574-3-miquel.raynal@bootlin.com> <2023052351-doze-purist-9780@gregkh> <20230523191402.0728443a@xps-13> <20230529121226.4a74a3bb@xps-13> <2023052953-average-fade-8b07@gregkh> <20230529153539.1c9aeee2@xps-13> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230529153539.1c9aeee2@xps-13> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 29, 2023 at 03:35:39PM +0200, Miquel Raynal wrote: > Hi Greg, > > gregkh@linuxfoundation.org wrote on Mon, 29 May 2023 14:05:30 +0100: > > > On Mon, May 29, 2023 at 12:12:26PM +0200, Miquel Raynal wrote: > > > Hi Greg, > > > > > > miquel.raynal@bootlin.com wrote on Tue, 23 May 2023 19:14:02 +0200: > > > > > > > Hi Greg, > > > > > > > > gregkh@linuxfoundation.org wrote on Tue, 23 May 2023 17:58:51 +0100: > > > > > > > > > On Tue, May 23, 2023 at 12:02:39PM +0200, Miquel Raynal wrote: > > > > > > +/* Cell attributes will be dynamically allocated */ > > > > > > +static struct attribute_group nvmem_cells_group = { > > > > > > + .name = "cells", > > > > > > +}; > > > > > > + > > > > > > static const struct attribute_group *nvmem_dev_groups[] = { > > > > > > &nvmem_bin_group, > > > > > > + NULL, /* Reserved for exposing cells, if any */ > > > > > > > > > > Please don't do this, but rather use the is_visible callback to > > > > > determine if it should be shown or not. > > > > > > > > Ah, excellent point. Don't know why I overlooked that member. > > > > > > Actually, the .is_visible callback only acts on the files and > > > not the directories (created based on the group name). > > > > That is true, I have a non-working patch somewhere around here that will > > not create the directory if no files are in that directory, and need to > > get that working someday... > > I see, indeed that would be a nice addition. > > > > This > > > means whether they are visible or not, the attributes must be > > > valid, the nvmem core cannot just toggle a boolean value with > > > .is_visible because the sysfs core makes a number of checks > > > regarding the content of the attributes, without checking if > > > they are visible at all. > > > > You can't toggle a value, that's not how is_visible works. It's a > > callback at the creation time, you do know if you should, or should not, > > show the files at creation time, right? > > I think I should be able to do that. > > > If so, all should be fine, just ignore the empty directory, it's fine. > > Ok. > > > And hopefully one day, it will not be created if there are no files in > > it. If I can ever get that patch working... > > > > > I can however expose the "cells" bin group by default by having > > > it listed in the static bin_attribute list and discard it by > > > overwriting the list member with NULL (ie. the opposite of the current > > > solution). > > > > Ick, no, please don't do that. attribute lists should be able to be put > > into read-only memory, and are not set up to be dynamically messed with > > like this at all. > > I get the idea, makes sense. > > However in my case, the list of attribute groups can lay into RO > memory, that's fine, but the attribute group for the cells > will not. Indeed, the .bin_attrs list must be populated at run time > as we do not know it's size at compilation time. Ick. I thought we had a way to update the size of a sysfs file dynamically but I guess not. So that's ok for now. thanks, greg k-h