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=-8.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 CFC73C4320D for ; Tue, 24 Sep 2019 04:50:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8E70121655 for ; Tue, 24 Sep 2019 04:50:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569300610; bh=G9RP+Qa3dNbYQldyep2Vb0GBoLFopZ+7tVc/FnTIKlQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=NTF9hVhz108YuXUjn5RNfLfI8ZXeHNamk2JPUmPJu8tzsf1sW1oiEERh70ZL957IV 2bMGcsz5c6l86bN9OJxndduC3B6/xiMT4fyP09omxB3x7x6nx6qIfik6zyJX1RFULs RvsMl9zLh4OG883Zrh5Qk8M9V0JmPBjavIBBWEUY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2408570AbfIXEuJ (ORCPT ); Tue, 24 Sep 2019 00:50:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:57316 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2394439AbfIXEuJ (ORCPT ); Tue, 24 Sep 2019 00:50:09 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8E6A0207FD; Tue, 24 Sep 2019 04:50:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569300608; bh=G9RP+Qa3dNbYQldyep2Vb0GBoLFopZ+7tVc/FnTIKlQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Nb8MS+IEqhMvhrlbvBw0bZaZ8fGhQdqJG7WWs5zsFdBiUlqYUdrDQ800F4hJwiixv wlE1LZT/jmCMEIRniIUEsGRaMdRt2cUwjgzEuSeLpLDQhLLg4PF0JDtIWxcV0q8MBC FVOqb7G8xPF8REzEg5yNQTkerUWwGsNuZxEy3YRw= Date: Tue, 24 Sep 2019 06:50:05 +0200 From: Greg KH To: mnalajal@codeaurora.org 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 Message-ID: <20190924045005.GB2700@kroah.com> References: <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> <20190920033651.GC63675@minitux> <20190920061006.GC473898@kroah.com> <5d9d1f3d11b1e4173990d4c5ac547193@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5d9d1f3d11b1e4173990d4c5ac547193@codeaurora.org> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 23, 2019 at 02:35:33PM -0700, mnalajal@codeaurora.org wrote: > On 2019-09-19 23:10, Greg KH wrote: > > On Thu, Sep 19, 2019 at 08:36:51PM -0700, Bjorn Andersson wrote: > > > On Thu 19 Sep 15:45 PDT 2019, 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. > > > > > > > > > > The difference between the two cases is that in the fsl-usb case it's > > > attributes of the device itself, while in the soc case the > > > realview-soc > > > driver (or the others doing this) calls soc_device_register() to > > > register a new (dangling) soc device, which it then adds its > > > attributes > > > onto. > > > > That sounds really really odd. Why can't the soc device do the creation > > "automatically" when the device is registered? The soc core should > > handle this for the soc "drivers", that's what it is there for. > > > Clients are registering to soc framework using "soce_device_register()" > with "soc_device_attribute". This attribute structure does not have all > the sysfs fields what client are interested. Hence clients are handling > their required sysfs fields in their drivers. > https://elixir.bootlin.com/linux/v5.3/source/drivers/base/soc.c#L114 Then you should fix that :) > > > We can't use dev_groups, because the soc_device (soc.c) isn't > > > actually a > > > driver and the list of attributes is a combination of things from > > > soc.c > > > and e.g. soc-realview.c. > > > > > > But if we pass a struct attribute_group into soc_device_register() and > > > then have that register both groups using dev.groups, this should be > > > much cleaner at least. > > > > Don't you have a structure you can store these in as well? > At present client is populating entries one-by-one > https://android.googlesource.com/kernel/msm/+/android-7.1.0_r0.2/drivers/soc/qcom/socinfo.c#1254 And that is known to be broken and racy and will cause problems with userspace. This should be fixed... thanks, greg k-h