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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 2F5B3ECE560 for ; Mon, 24 Sep 2018 15:51:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D3A8F20870 for ; Mon, 24 Sep 2018 15:51:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D3A8F20870 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=st.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730116AbeIXVyU (ORCPT ); Mon, 24 Sep 2018 17:54:20 -0400 Received: from mx08-00178001.pphosted.com ([91.207.212.93]:23184 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728280AbeIXVyT (ORCPT ); Mon, 24 Sep 2018 17:54:19 -0400 Received: from pps.filterd (m0046660.ppops.net [127.0.0.1]) by mx08-.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id w8OFn4Bd027910; Mon, 24 Sep 2018 17:50:51 +0200 Received: from beta.dmz-eu.st.com (beta.dmz-eu.st.com [164.129.1.35]) by mx08-00178001.pphosted.com with ESMTP id 2mnav5byjv-1 (version=TLSv1 cipher=ECDHE-RSA-AES256-SHA bits=256 verify=NOT); Mon, 24 Sep 2018 17:50:50 +0200 Received: from zeta.dmz-eu.st.com (zeta.dmz-eu.st.com [164.129.230.9]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id F24193A; Mon, 24 Sep 2018 15:50:49 +0000 (GMT) Received: from Webmail-eu.st.com (sfhdag5node3.st.com [10.75.127.15]) by zeta.dmz-eu.st.com (STMicroelectronics) with ESMTP id C761AAA21; Mon, 24 Sep 2018 15:50:49 +0000 (GMT) Received: from [10.48.0.167] (10.75.127.46) by SFHDAG5NODE3.st.com (10.75.127.15) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 24 Sep 2018 17:50:48 +0200 Subject: Re: [RESEND PATCH] Revert "pwm: Set class for exported channels in sysfs" To: Thierry Reding CC: , , , , , , , , , References: <1537538567-5377-1-git-send-email-fabrice.gasnier@st.com> <20180924115301.GV21032@ulmo> <20180924142318.GG23547@ulmo> From: Fabrice Gasnier Message-ID: Date: Mon, 24 Sep 2018 17:50:48 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180924142318.GG23547@ulmo> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.75.127.46] X-ClientProxiedBy: SFHDAG3NODE3.st.com (10.75.127.9) To SFHDAG5NODE3.st.com (10.75.127.15) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-09-24_09:,, signatures=0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/24/2018 04:23 PM, Thierry Reding wrote: > On Mon, Sep 24, 2018 at 03:59:03PM +0200, Fabrice Gasnier wrote: >> On 09/24/2018 01:53 PM, Thierry Reding wrote: >>> On Fri, Sep 21, 2018 at 04:02:47PM +0200, Fabrice Gasnier wrote: >>>> This reverts commit 7e5d1fd75c3dde9fc10c4472b9368089d1b81d00 as it causes >>>> regression with multiple pwm chip. It creates a new entry in >>>> '/sys/class/pwm' every time a 'pwmX' is exported with 'echo X > export': >>>> - 1st time export will create an entry in /sys/class/pwm/pwmX >>>> - when another export happens on another pwmchip, it can't be created >>>> (e.g. -EEXIST) >>>> >>>> This also changes existing ABI (Documentation/ABI/testing/sysfs-class-pwm): >>>> - pmwX should be there: /sys/class/pwm/pwmchipN/pwmX >>>> >>>> Example on stm32 (stm32429i-eval) platform: >>>> $ ls /sys/class/pwm >>>> pwmchip0 pwmchip4 >>>> >>>> $ cd /sys/class/pwm/pwmchip0/ >>>> $ echo 0 > export >>>> $ ls /sys/class/pwm >>>> pwm0 pwmchip0 pwmchip4 >>>> >>>> $ cd /sys/class/pwm/pwmchip4/ >>>> $ echo 0 > export >>>> sysfs: cannot create duplicate filename '/class/pwm/pwm0' >>>> ...Exception stack follows... >>>> >>>> Signed-off-by: Fabrice Gasnier >>>> --- >>>> drivers/pwm/sysfs.c | 1 - >>>> 1 file changed, 1 deletion(-) >>> >>> Can we come up with an alternative that allows us to have both? We want >>> uevent and proper sysfs creation, or is that not possible? >> >> Hi Thierry, all, >> >> With current approach: >> - "export->child.class = parent->class" >> - ABI (e.g. "pwm%d") device name isn't unique with multiple pwm chip. >> I think this is not possible. >> >> Trying to think of an alternative... I just did a quick test, by >> changing device name, to take pwmchip into account: >> + export->child.class = parent->class; >> export->child.release = pwm_export_release; >> export->child.parent = parent; >> export->child.devt = MKDEV(0, 0); >> export->child.groups = pwm_groups; >> - dev_set_name(&export->child, "pwm%u", pwm->hwpwm); >> + dev_set_name(&export->child, "pwmchip%d-pwm%u", chip->base, >> pwm->hwpwm); >> >> But this also impacts existing ABI :-( >> Would you have suggestions to send an uevent, without modifying ABI ? > > I don't quite understand why, in the example you show in the commit > message, the pwmX nodes appear in the top-level /sys/class/pwm > directory. According to Documentation/ABI/testing/sysfs-class-pwm they > should appear as /sys/class/pwm/pwmchipN/pwmX. I can only imagine that > setting the class may have changed that. Yes, adding the class makes the link to be created under /sys/class/pwm: device_register() -> device_add() -> device_add_class_symlinks() In device_add_class_symlinks(): ... if (!dev->class) return 0; ... /* link in the class directory pointing to the device */ error = sysfs_create_link(&dev->class->p->subsys.kobj, &dev->kobj, dev_name(dev)); ... > If so, perhaps we can > workaround that by creating a new class that is not parent->class? And this link is added using dev_name(). So I doubt adding a new class will change the current behavior. > > Thierry >