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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 70201C10F11 for ; Wed, 24 Apr 2019 12:35:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4C22E218D2 for ; Wed, 24 Apr 2019 12:35:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730004AbfDXMfO (ORCPT ); Wed, 24 Apr 2019 08:35:14 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:6688 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726167AbfDXMfN (ORCPT ); Wed, 24 Apr 2019 08:35:13 -0400 Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id C9DDA6A2E55615EA1F56; Wed, 24 Apr 2019 20:35:11 +0800 (CST) Received: from localhost (10.202.226.61) by DGGEMS413-HUB.china.huawei.com (10.3.19.213) with Microsoft SMTP Server id 14.3.439.0; Wed, 24 Apr 2019 20:35:07 +0800 Date: Wed, 24 Apr 2019 13:34:55 +0100 From: Jonathan Cameron To: "Ardelean, Alexandru" CC: "gregkh@linuxfoundation.org" , "namhyung@kernel.org" , "linux-kernel@vger.kernel.org" , "andriy.shevchenko@linux.intel.com" , "linux-iio@vger.kernel.org" , "mingo@kernel.org" Subject: Re: [PATCH 1/2] lib: add __sysfs_match_string_with_gaps() helper Message-ID: <20190424133455.00002909@huawei.com> In-Reply-To: <86ea407aaa891e50a3bdaf2c3653636a365076ee.camel@analog.com> References: <20190422083257.21805-1-alexandru.ardelean@analog.com> <20190422210606.GA8805@kroah.com> <86ea407aaa891e50a3bdaf2c3653636a365076ee.camel@analog.com> Organization: Huawei X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; i686-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.226.61] X-CFilter-Loop: Reflected Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org On Tue, 23 Apr 2019 06:38:44 +0000 "Ardelean, Alexandru" wrote: > On Mon, 2019-04-22 at 23:06 +0200, Greg KH wrote: > > > > > > On Mon, Apr 22, 2019 at 11:32:56AM +0300, Alexandru Ardelean wrote: > > > This helper is similar to __sysfs_match_string() with the exception > > > that it > > > ignores NULL elements within the array. > > > > sysfs is "one value per file", why are you trying to write multiple > > things on a single line to a single sysfs file? > > > > Is IIO really that messy? :) > > > > Hmm, I don't think I understood the comment/question, or maybe I did not > formulate the comment properly. > > Maybe Jonathan can pitch-in here if I'm saying something wrong. > > So, in IIO there is `struct iio_enum` which is essentially a sysfs wrapper > for exposing an "enum" type to userspace via sysfs (which takes only one > value). This iio_enum type is basically a string-to-int mapping. > > Some example in C: > > enum { > ENUM0, > ENUM1, > ENUM5 = 5, > ENUM6, > ENUM7 > }; > > > /* Notice the gaps in the elements */ > static const char * const item_strings[] = { > [ENUM0] = "mode0", > [ENUM1] = "mode1", > [ENUM5] = "mode5", > [ENUM6] = "mode6", > [ENUM7] = "mode7", > }; > > static const struct iio_enum iio_enum1 = { > .items = item_strings, > .num_items = ARRAY_SIZE(item_strings), > .set = iio_enum1_set, > .get = iio_enum1_get, > }; > > > The signature of the iio_enum1_set / iio_enum1_get is below: > > static int iio_enum1_set(struct iio_dev *indio_dev, > const struct iio_chan_spec *chan, unsigned int val); > > static int iio_enum1_get(struct iio_dev *indio_dev, > const struct iio_chan_spec *chan) > > > IIO core resolves the string-to-int mapping. > It uses __sysfs_match_string() to do that, but it requires that the list of > strings (and C enums) be contiguous. > This change [and V2 of this patch] introduces a > __sysfs_match_string_with_gaps() helper that ignores gaps (represented as > NULLs). > > For reference, __sysfs_match_string() returns -EINVAL on the first NULL in > the array of strings (regardless of the given array size). > > __sysfs_match_string_with_gaps() is typically helpful when C enums refer to > bitfields, or have some equivalence in HW. > You have described it well. Perhaps the issue is in the naming? Or more description is needed for the original patch. It's worth highlighting that the current help text for __sysfs_match_string has a description that says: /** * __sysfs_match_string - matches given string in an array * @array: array of strings * @n: number of strings in the array or -1 for NULL terminated arrays * @str: string to match with * * Returns index of @str in the @array or -EINVAL, just like match_string(). * Uses sysfs_streq instead of strcmp for matching. */ so one could argue that if you pass a value of n which is not -1 the function should not assume that any NULL terminates the array... So basically this new function is implementing what I would have assumed __sysfs_match_string would do, but doesn't. Jonathan > Thanks > Alex > > > thanks, > > > > greg k-h