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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 7913EC4360F for ; Fri, 22 Feb 2019 09:51:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 480C22086C for ; Fri, 22 Feb 2019 09:51:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="JhEFVJ5N" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726942AbfBVJv5 (ORCPT ); Fri, 22 Feb 2019 04:51:57 -0500 Received: from perceval.ideasonboard.com ([213.167.242.64]:57282 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726218AbfBVJv5 (ORCPT ); Fri, 22 Feb 2019 04:51:57 -0500 Received: from pendragon.ideasonboard.com (dfj612yhrgyx302h3jwwy-3.rev.dnainternet.fi [IPv6:2001:14ba:21f5:5b00:ce28:277f:58d7:3ca4]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id C9E6D49; Fri, 22 Feb 2019 10:51:54 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1550829115; bh=FZivtZvNhvBEpNCgWk/P6hAdkG9BRSP4aHrmPCbVZ9o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JhEFVJ5NW4f/jX5Pmn3PqYkXLn/Of6dh/gpvGDLw1VnGFV+X6OcaEvOu8/Wfnjs2F pFMgb1oGB3myDsTZVEKmIkLYEd01i2Gig/R6PxCvvSuvbhSeCdWTG9kdSpYTqcAqkM he1TKq9ITFQQfBITmrSrCwFNxI7G1lNMhMCMjAfk= Date: Fri, 22 Feb 2019 11:51:45 +0200 From: Laurent Pinchart To: Greg KH Cc: Bjorn Andersson , Vaishali Thakkar , andy.gross@linaro.org, david.brown@linaro.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, rafael@kernel.org, vkoul@kernel.org Subject: Re: [PATCH v2 3/5] soc: qcom: socinfo: Expose custom attributes Message-ID: <20190222095145.GA3522@pendragon.ideasonboard.com> References: <20190220045829.6852-1-vaishali.thakkar@linaro.org> <20190221121841.GA32108@pendragon.ideasonboard.com> <20190221155742.GD2122@tuxbook-pro> <20190221221359.GD3485@pendragon.ideasonboard.com> <20190222071616.GA2306@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190222071616.GA2306@kroah.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Greg, On Fri, Feb 22, 2019 at 08:16:16AM +0100, Greg KH wrote: > On Fri, Feb 22, 2019 at 12:13:59AM +0200, Laurent Pinchart wrote: > > On Thu, Feb 21, 2019 at 07:57:42AM -0800, Bjorn Andersson wrote: > > > On Thu 21 Feb 04:18 PST 2019, Laurent Pinchart wrote: > > > > On Wed, Feb 20, 2019 at 10:28:29AM +0530, Vaishali Thakkar wrote: > > > > > The Qualcomm socinfo provides a number of additional attributes, > > > > > add these to the socinfo driver and expose them via debugfs > > > > > functionality. > > > > > > > > What is the use case for these attributes ? I fear they will be used in > > > > production systems, and that would require debugfs in production, which > > > > isn't a good idea. If you need to expose those attributes for anything > > > > else than debugging then we need a proper API, likely sysfs-based. > > > > > > The use case of these attributes, beyond development/debugging, are > > > unfortunately somewhat unknown and is the reason why they where moved to > > > debugfs from the earlier attempts to upstream this. > > > > > > I think the production requirements at hand prohibits debugfs to be > > > present, so attributes that are required beyond development/debugging > > > purposes would have to be migrated out to sysfs - but the idea here is > > > that such migration would have come with the missing motivation to add > > > them there today. > > > > If the use case is just debug/development, would it be enough to print > > this information in the kernel log at boot time ? I may be a bit > > paranoid, but I always worry about API abuse :-( > > Putting stuff in debugfs should be fine. No system should ever rely on > debugfs for a properly running system as it is being disabled on almost > all "sane" systems (Android included). If a vendor relies on this > information for a properly working system, then it does not belong in > debugfs. There's certainly no disagreement about that, my concern is about vendors who will enable debugfs to access information they need just because it's there. Do I assume correctly we can "break the debugfs ABI" in mainline by changing the format of the information if needed ? -- Regards, Laurent Pinchart