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=-6.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 3BC06C4CEC4 for ; Thu, 19 Sep 2019 23:39:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0826421920 for ; Thu, 19 Sep 2019 23:39:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="d/MLPwEB"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="fcaT3HBO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390897AbfISXjb (ORCPT ); Thu, 19 Sep 2019 19:39:31 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:45508 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390217AbfISXja (ORCPT ); Thu, 19 Sep 2019 19:39:30 -0400 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 6751E6118C; Thu, 19 Sep 2019 23:39:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1568936368; bh=/N5LA3VZRheX/0Vim93hGoS5MshyffKsHn+ugEInpsU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=d/MLPwEBBiqRT+DvBnqFclfRSiEfy5PaUKHX9mJZE1KDQLd/7ydZMsIPHhZBOqcHF yE8iMG9AWvOPwgo7ID04znjQZpj4K+DsLal1e2Q51GzwEPkpKVQYYKXtRomLqvdP2P aN8bEOZI8Ga8VUPhDEN8kpSP+Zr8rPaU1USvRTKQ= Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.codeaurora.org (Postfix) with ESMTP id 80DB561197; Thu, 19 Sep 2019 23:39:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1568936367; bh=/N5LA3VZRheX/0Vim93hGoS5MshyffKsHn+ugEInpsU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=fcaT3HBOanXCmHj2+Xb2t7at/xuhDH6/FyHlyTAReApGsnPC8QmNm9Xb+PXi8QCkT 8gu/S7l1I/tM8CwrGm2PBCrjGqaXZbzu8uUbVv2tr8QGGRKJAsdn+WvUgvSfidFl4Y 4ImccfN01246ZwoVDIeWwlG0zmrvA/xO6msMyu7g= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 19 Sep 2019 16:39:27 -0700 From: mnalajal@codeaurora.org To: Greg KH Cc: Bjorn Andersson , rafael@kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Walleij Subject: Re: [PATCH] base: soc: Export soc_device_to_device API In-Reply-To: <20190919224514.GA447028@kroah.com> References: <1568927624-13682-1-git-send-email-mnalajal@codeaurora.org> <20190919213203.GA395325@kroah.com> <20190919215300.GC1418@minitux> <20190919215836.GA426988@kroah.com> <20190919221456.GA63675@minitux> <20190919222525.GA445429@kroah.com> <20190919224017.GB63675@minitux> <20190919224514.GA447028@kroah.com> Message-ID: X-Sender: mnalajal@codeaurora.org User-Agent: Roundcube Webmail/1.2.5 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019-09-19 15:45, Greg KH wrote: > On Thu, Sep 19, 2019 at 03:40:17PM -0700, Bjorn Andersson wrote: >> On Thu 19 Sep 15:25 PDT 2019, Greg KH wrote: >> >> > On Thu, Sep 19, 2019 at 03:14:56PM -0700, Bjorn Andersson wrote: >> > > On Thu 19 Sep 14:58 PDT 2019, Greg KH wrote: >> > > >> > > > On Thu, Sep 19, 2019 at 02:53:00PM -0700, Bjorn Andersson wrote: >> > > > > On Thu 19 Sep 14:32 PDT 2019, Greg KH wrote: >> > > > > >> > > > > > On Thu, Sep 19, 2019 at 02:13:44PM -0700, Murali Nalajala wrote: >> > > > > > > If the soc drivers want to add custom sysfs entries it needs to >> > > > > > > access "dev" field in "struct soc_device". This can be achieved >> > > > > > > by "soc_device_to_device" API. Soc drivers which are built as a >> > > > > > > module they need above API to be exported. Otherwise one can >> > > > > > > observe compilation issues. >> > > > > > > >> > > > > > > Signed-off-by: Murali Nalajala >> > > > > > > --- >> > > > > > > drivers/base/soc.c | 1 + >> > > > > > > 1 file changed, 1 insertion(+) >> > > > > > > >> > > > > > > diff --git a/drivers/base/soc.c b/drivers/base/soc.c >> > > > > > > index 7c0c5ca..4ad52f6 100644 >> > > > > > > --- a/drivers/base/soc.c >> > > > > > > +++ b/drivers/base/soc.c >> > > > > > > @@ -41,6 +41,7 @@ struct device *soc_device_to_device(struct soc_device *soc_dev) >> > > > > > > { >> > > > > > > return &soc_dev->dev; >> > > > > > > } >> > > > > > > +EXPORT_SYMBOL_GPL(soc_device_to_device); >> > > > > > > >> > > > > > > static umode_t soc_attribute_mode(struct kobject *kobj, >> > > > > > > struct attribute *attr, >> > > > > > >> > > > > > What in-kernel driver needs this? >> > > > > > >> > > > > >> > > > > Half of the drivers interacting with the soc driver calls this API, >> > > > > several of these I see no reason for being builtin (e.g. >> > > > > ux500 andversatile). So I think this patch makes sense to allow us to >> > > > > build these as modules. >> > > > > >> > > > > > Is linux-next breaking without this? >> > > > > > >> > > > > >> > > > > No, we postponed the addition of any sysfs attributes in the Qualcomm >> > > > > socinfo driver. >> > > > > >> > > > > > We don't export things unless we have a user of the export. >> > > > > > >> > > > > > Also, adding "custom" sysfs attributes is almost always not the correct >> > > > > > thing to do at all. The driver should be doing it, by setting up the >> > > > > > attribute group properly so that the driver core can do it automatically >> > > > > > for it. >> > > > > > >> > > > > > No driver should be doing individual add/remove of sysfs files. If it >> > > > > > does so, it is almost guaranteed to be doing it incorrectly and racing >> > > > > > userspace. >> > > > > > >> > > > > >> > > > > The problem here is that the attributes are expected to be attached to >> > > > > the soc driver, which is separate from the platform-specific drivers. So >> > > > > there's no way to do platform specific attributes the right way. >> > > > > >> > > > > > And yes, there's loads of in-kernel examples of doing this wrong, I've >> > > > > > been working on fixing that up, look at the patches now in Linus's tree >> > > > > > for platform and USB drivers that do this as examples of how to do it >> > > > > > right. >> > > > > > >> > > > > >> > > > > Agreed, this patch should not be used as an approval for any crazy >> > > > > attributes; but it's necessary in order to extend the soc device's >> > > > > attributes, per the current design. >> > > > >> > > > Wait, no, let's not let the "current design" remain if it is broken! >> > > > >> > > > Why can't the soc driver handle the attributes properly so that the >> > > > individual driver doesn't have to do the create/remove? >> > > > >> > > >> > > The custom attributes that these drivers want to add to the common ones >> > > are known in advance, so I presume we could have them passed into >> > > soc_device_register() and registered together with the common >> > > attributes... >> > > >> > > It sounds like it's worth a prototype. >> > >> > Do you have an in-kernel example I can look at to get an idea of what is >> > needed here? >> > >> >> realview_soc_probe(), in drivers/soc/versatile/soc-realview.c, >> implements the current mechanism of acquiring the soc's struct device >> and then issuing a few device_create_file calls on that. > > That looks to be a trivial driver to fix up. Look at 6d03c140db2e > ("USB: phy: fsl-usb: convert platform driver to use dev_groups") as an > example of how to do this. > > Also gotta love the total lack of error checking when calling > device_create_file() in that driver :( > > thanks, > > greg k-h You can see example here https://android.googlesource.com/kernel/msm/+/android-7.1.0_r0.2/drivers/soc/qcom/socinfo.c#1356 I want to add the custom entries to "soc" device path. This can be achieved if i go with "dev_groups"? sys/devices/soc0 # ls -l total 0 -r--r--r-- 1 root 0 4096 Jan 1 00:01 family -r--r--r-- 1 root 0 4096 Jan 1 00:01 machine drwxr-xr-x 2 root 0 0 Jan 1 00:01 power -r--r--r-- 1 root 0 4096 Jan 1 00:01 revision -r--r--r-- 1 root 0 4096 Jan 1 00:01 serial_number lrwxrwxrwx 1 root 0 0 Jan 1 00:01 subsystem -> ../../bus/soc -rw-r--r-- 1 root 0 4096 Jan 1 00:01 uevent