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[104.188.17.28]) by smtp.gmail.com with ESMTPSA id 30sm6417430pjk.25.2019.09.19.14.53.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Sep 2019 14:53:02 -0700 (PDT) Date: Thu, 19 Sep 2019 14:53:00 -0700 From: Bjorn Andersson To: Greg KH Cc: Murali Nalajala , 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: <20190919215300.GC1418@minitux> References: <1568927624-13682-1-git-send-email-mnalajal@codeaurora.org> <20190919213203.GA395325@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190919213203.GA395325@kroah.com> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. So: Reviewed-by: Bjorn Andersson Regards, Bjorn