From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from metis.whiteo.stw.pengutronix.de (metis.whiteo.stw.pengutronix.de [185.203.201.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3E6AC1BEF82 for ; Tue, 21 Jan 2025 10:26:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.203.201.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737455206; cv=none; b=TvVuoOhQYQFSzIPBXCObbef+ywZuQPeCGsQ8R7IyRAoygORQQXvmfP/Ztuoli4HfXGuLAmTsDapi3q3JoMewKZsfW5Y91swjmIpUCMu1AYlF22sZ783AUGbxdgtOXpFF0Y+yA4nlapYd0rLeRmottnISqtnohZa8j8t2q5CxaAA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737455206; c=relaxed/simple; bh=+GwUqLVv9UiG81Eik2G/N+A+U9sjJV2P+7G7dsBseQE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=evVnW10Jb5O4Uz9Dth+xiqJt+t0KMqYXqroRrW+lXCwef497hh8iI1pijXv0Whf2Se6mDvYAuOVYOVMEXdMPUanmHUKyKNCYvcX6SHUHI9LqdcpwLpiA3eULzWVyI5S4PMrh7zJ74Z4G331RrP98J3Zyzv5LbDkmu64JbMSNy0c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de; spf=pass smtp.mailfrom=pengutronix.de; arc=none smtp.client-ip=185.203.201.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pengutronix.de Received: from ptz.office.stw.pengutronix.de ([2a0a:edc0:0:900:1d::77] helo=[127.0.0.1]) by metis.whiteo.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1taBSt-0006uR-6B; Tue, 21 Jan 2025 11:26:35 +0100 Message-ID: <449b4618-7d06-49c8-b521-5fdd02a2ba1b@pengutronix.de> Date: Tue, 21 Jan 2025 11:26:33 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] gpiolib: add opt-out for existing drivers with static GPIO base To: Kent Gibson Cc: Andy Shevchenko , Linus Walleij , Bartosz Golaszewski , Andy Whitcroft , Joe Perches , Dwaipayan Ray , Lukas Bulwahn , Fabio Estevam , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Dario Binacchi , Haibo Chen , Catalin Popescu , linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org References: <20250113-b4-imx-gpio-base-warning-v1-0-0a28731a5cf6@pengutronix.de> <20250113-b4-imx-gpio-base-warning-v1-1-0a28731a5cf6@pengutronix.de> <97baffcd-35cc-49a0-95e9-d1ceac966dc3@pengutronix.de> <40531a5e-993f-4532-b071-6f233d6923f8@pengutronix.de> <20250115130432.GA159787@rigel> Content-Language: en-US From: Ahmad Fatoum In-Reply-To: <20250115130432.GA159787@rigel> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 2a0a:edc0:0:900:1d::77 X-SA-Exim-Mail-From: a.fatoum@pengutronix.de X-SA-Exim-Scanned: No (on metis.whiteo.stw.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Hi Kent, On 15.01.25 14:04, Kent Gibson wrote: > On Wed, Jan 15, 2025 at 08:07:38AM +0100, Ahmad Fatoum wrote: >> On 14.01.25 20:38, Andy Shevchenko wrote: >>> On Tue, Jan 14, 2025 at 12:06 PM Ahmad Fatoum wrote: >>>> On 14.01.25 10:49, Andy Shevchenko wrote: >>>>> On Tue, Jan 14, 2025 at 12:20 AM Ahmad Fatoum wrote: >>>>>> >>>>>> Some drivers have had deterministic GPIO numbering for most of >>>>>> their existence, e.g. the i.MX GPIO since commit 7e6086d9e54a >>>>>> ("gpio/mxc: specify gpio base for device tree probe"), more than >>>>>> 12 years ago. >>>>>> >>>>>> Reverting this to dynamically numbered will break existing setups in >>>>>> the worst manner possible: The build will succeed, the kernel will not >>>>>> print warnings, but users will find their devices essentially toggling >>>>>> GPIOs at random with the potential of permanent damage. >>>>>> >>>>>> As these concerns won't go away until the sysfs interface is removed, >>>>>> let's add a new struct gpio_chip::legacy_static_base member that can be >>>>>> used by existing drivers that have been grandfathered in to suppress >>>>>> the warning currently being printed: >>>>>> >>>>>> gpio gpiochip0: Static allocation of GPIO base is deprecated, >>>>>> use dynamic allocation. >>>>> >>>>> Warning is harmless and still a good reminder for the stuff that needs >>>>> more love. >>>>> NAK. >>>> >>>> A warning is a call-to-action and it's counterproductive to keep tricking >>>> people into removing the static base and breaking other users' scripts. >>> >>> Are you prepared to say the same when the entire GPIO SYSFS will be >>> removed? Because that's exactly what I referred to in the reply to the >>> cover letter as an impediment to move forward. >> >> No. But this gives me an idea: We could make the warning dependent >> on CONFIG_GPIO_SYSFS and add a comment to the i.MX code suggesting >> users do that instead. What do you think? >> > > AIUI, the purpose of the warning is to remind driver authors, not end users, > to update their drivers, as the old behaviour is deprecated. That is > independent of GPIO SYSFS - that just happens to be something that makes the > change visible to userspace. > > Rather than making the warning conditional, how about making the fix for the > warning in your driver, so switching to dynamic allocation, conditional on > CONFIG_GPIO_SYSFS not being set? > That would provide a path forward for users that want to dispense with > the warning - as long as they dispense with GPIO SYSFS. That could work for gpio-mxc, provided that SysFS is the only user for which the static base matters. I assume that's the case, but I am not sure. An argument for suppressing the warning selectively in the GPIO core is that this doesn't only affect gpio-mxc, but also e.g. gpio-zynq or gpio-mxs. Cheers, Ahmad > > Cheers, > Kent. > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |