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 DA0ACC433FE for ; Fri, 14 Oct 2022 13:22:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229723AbiJNNWj (ORCPT ); Fri, 14 Oct 2022 09:22:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33668 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229671AbiJNNWi (ORCPT ); Fri, 14 Oct 2022 09:22:38 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94AC72D1DA; Fri, 14 Oct 2022 06:22:36 -0700 (PDT) Received: from fraeml745-chm.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4Mpn940Ssnz6HJMW; Fri, 14 Oct 2022 21:21:44 +0800 (CST) Received: from lhrpeml500005.china.huawei.com (7.191.163.240) by fraeml745-chm.china.huawei.com (10.206.15.226) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Fri, 14 Oct 2022 15:22:34 +0200 Received: from localhost (10.202.226.42) by lhrpeml500005.china.huawei.com (7.191.163.240) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Fri, 14 Oct 2022 14:22:33 +0100 Date: Fri, 14 Oct 2022 14:22:32 +0100 From: Jonathan Cameron To: "Vaittinen, Matti" CC: Andy Shevchenko , Jonathan Cameron , Matti Vaittinen , "Lars-Peter Clausen" , Rob Herring , "Krzysztof Kozlowski" , Jagath Jog J , Nikita Yushchenko , Cosmin Tanislav , "linux-iio@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC PATCH v2 4/5] iio: accel: Support Kionix/ROHM KX022A accelerometer Message-ID: <20221014142232.000038df@huawei.com> In-Reply-To: <7abed64a-d544-a228-b5f1-4c7b5a3bd1be@fi.rohmeurope.com> References: <88e24b01da9f44ebf5fcd8344ded0b75ff742fbf.1665066397.git.mazziesaccount@gmail.com> <20221009133351.6ff4894b@jic23-huawei> <7abed64a-d544-a228-b5f1-4c7b5a3bd1be@fi.rohmeurope.com> X-Mailer: Claws Mail 4.0.0 (GTK+ 3.24.29; i686-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.226.42] X-ClientProxiedBy: lhrpeml500003.china.huawei.com (7.191.162.67) To lhrpeml500005.china.huawei.com (7.191.163.240) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Tue, 11 Oct 2022 09:10:21 +0000 "Vaittinen, Matti" wrote: > On 10/10/22 09:15, Andy Shevchenko wrote: > > On Sun, Oct 09, 2022 at 01:33:51PM +0100, Jonathan Cameron wrote: > >> On Thu, 6 Oct 2022 21:32:11 +0300 Andy Shevchenko > >> wrote: > >>> On Thu, Oct 06, 2022 at 05:38:14PM +0300, Matti Vaittinen wrote: > > > > ... > > > >>>> +module_param(g_kx022a_use_buffer, bool, 0); > >>>> +MODULE_PARM_DESC(g_kx022a_use_buffer, + "Buffer samples. Use > >>>> at own risk. Fifo must not overflow"); > >>> > >>> Why?! We usually do not allow module parameters in the new code. > >> > >> Badly broken hardware - was my suggestion. Alternatives if there > >> are usecases that need to use the fifo, but it can wedge hard in a > >> fashion that is impossible to prevent from the driver? My gut > >> feeling is still drop the support entirely with a strong comment in > >> the code that the hardware is broken in a fashion we don't know how > >> to work around. > > I did some quick study regarding couple of other Kionix sensors. (like > KX122 and old KX022 - without the 'A'). It seems to me that the register > interfaces between many of the sensors are largely identical. Extending > the driver to support those seems pretty straightforward (scales and > resolution may need tweaking, as does the FIFO size) but register > contents and even offsets are largely identical. Last kionix part I had was a kxsd9 and I don't recall that having a fifo so obviously didn't hit this issue. > > As said, it seems the Kionix sensors may have different size of internal > FIFOs, or even no FIFO at all. So, maybe we could provide a > "kionix,fifo-enable" flag (or even "kionix,fifo-size") from device-tree? For device where we don't have reports of this issue, that should be derived from the compatible (or even better a whoami register if there is one). The driver should know the fifo-size if it isn't discoverable. > This would be a way to have the FIFO disabled by default and warn users > via dt-binding docs if they decide to explicitly enable the FIFO. > (Besides, I believe the FIFO is usable on at least some of the Kionix > sensors - because I've heard it is used on a few platforms). > > This could give us safe defaults while not shutting the doors from those > who wish to use the FIFO. Sure we need a buy-in from Krzysztof / Rob, > but that may be less of an obstacle compared to the module param if Greg > is so strongly oppsoing those. (And the dt-property could also provide > some technical merites as these sensors seem to really have differencies > in FIFOs). I'm dubious about having this for known broken parts - but I guess you can propose it and see what the dt-maintainers say. I don't want to see fifo size in the dt binding though. > > > > > I also would drop this from upstream and if anybody curious, provide > > some kind of GitHub gist for that. > > Well, I think we all agree that downstream code hosted in some > unofficial github repositories are rarely that valuable. They're less > reliable, less tested, less reviewed, less secure and pretty much > impossible to maintain in a way that interested user could get a version > matching his preferred kernel. > > There are reasons why I (people) keep sending the drivers to upstream - > and why some companies even spend $$ for that. Having this feature in > downstream repo is not nearly on same page for user's point of view as > is having the support upstream. It's not really support if it comes with big warnings and potentially we even taint the kernel of someone turns it on... > > > Also it needs some communication > > with a vendor to clarify the things. > > I do communication with the vendor on a daily basis :] Nowadays Kionix > is part of ROHM, and Finland SWDC has been collaboration with Kionix > even before they "merged" (but I have not been part of the "sensor team" > back then). > > Unfortunately, reaching the correct people inside the company is hard > and occasionally impossible - long story... :) Jonathan