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 7F6AAC433FE for ; Mon, 22 Nov 2021 11:20:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238391AbhKVLYC (ORCPT ); Mon, 22 Nov 2021 06:24:02 -0500 Received: from mga06.intel.com ([134.134.136.31]:41952 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229516AbhKVLX5 (ORCPT ); Mon, 22 Nov 2021 06:23:57 -0500 X-IronPort-AV: E=McAfee;i="6200,9189,10175"; a="295577131" X-IronPort-AV: E=Sophos;i="5.87,254,1631602800"; d="scan'208";a="295577131" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Nov 2021 03:20:51 -0800 X-IronPort-AV: E=Sophos;i="5.87,254,1631602800"; d="scan'208";a="674029881" Received: from smile.fi.intel.com ([10.237.72.184]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Nov 2021 03:20:50 -0800 Received: from andy by smile.fi.intel.com with local (Exim 4.95) (envelope-from ) id 1mp7NN-009Pk1-MS; Mon, 22 Nov 2021 13:20:45 +0200 Date: Mon, 22 Nov 2021 13:20:45 +0200 From: Andy Shevchenko To: Bartosz Golaszewski Cc: Linus Walleij , "open list:GPIO SUBSYSTEM" , Linux Kernel Mailing List Subject: Re: [PATCH v2 2/2] gpiolib: check the 'ngpios' property in core gpiolib code Message-ID: References: <20211118132317.15898-1-brgl@bgdev.pl> <20211118132317.15898-2-brgl@bgdev.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 19, 2021 at 08:35:33PM +0100, Bartosz Golaszewski wrote: > On Thu, Nov 18, 2021 at 10:16 PM Andy Shevchenko > wrote: > > On Thu, Nov 18, 2021 at 09:12:59PM +0100, Bartosz Golaszewski wrote: > > > On Thu, Nov 18, 2021 at 6:06 PM Andy Shevchenko > > > wrote: > > > > On Thu, Nov 18, 2021 at 02:23:17PM +0100, Bartosz Golaszewski wrote: ... > > > > > if (gc->ngpio == 0) { > > > > > - chip_err(gc, "tried to insert a GPIO chip with zero lines\n"); > > > > > - ret = -EINVAL; > > > > > - goto err_free_descs; > > > > > + ret = device_property_read_u32(&gdev->dev, "ngpios", &ngpios); > > > > > + if (ret) { > > > > > + chip_err(gc, "tried to insert a GPIO chip with zero lines\n"); > > > > > + ret = -EINVAL; > > > > > + goto err_free_descs; > > > > > + } > > > > > + > > > > > + gc->ngpio = ngpios; > > > > > } > > > > > > > > This should be > > > > > > > > if (gc->ngpio == 0) { > > > > ret = device_property_read_u32(&gdev->dev, "ngpios", &ngpios); > > > > if (ret) > > > > return ret; > > > > > > But device_property_read_u32() returning -ENODATA means there's no > > > such property, which should actually be converted to -EINVAL as the > > > caller wanting to create the chip provided invalid configuration - in > > > this case: a chip with 0 lines. In case of the non-array variant of > > > read_u32 that's also the only error that can be returned so this bit > > > looks right to me. > > > > So, what is so special about -EINVAL? Why -ENODATA is not good enough which > > will exactly explain to the caller what's going on, no? > > > > Let's imagine the user sets gc->ngpio = 0 incorrectly thinking it'll > make gpiolib set it to some sane default. Then gpiochip_add_data() > returns -ENODATA (No data available). This is confusing IMO. But if we > convert it to -EINVAL, it now says "Invalid value" which points to the > wrong configuration. > > ENODATA means "device tree property is not present" in this case but > the problem is that user supplies the gpiolib with invalid > configuration. EINVAL is the right error here. Then be explicit, don't shadow other error codes from fwnode API. if (ret && ret != -ENODATA) > > > > gc->ngpio = ngpios; > > > > } > > > > > > > > if (gc->ngpio == 0) { > > > > chip_err(gc, "tried to insert a GPIO chip with zero lines\n"); > > > > ret = -EINVAL; > > > > goto err_free_descs; > > > > When the caller intended to create a chip with 0 GPIOs they will get an error > > as you wish with an error message. > > Yes, as it was before. -- With Best Regards, Andy Shevchenko