On Thu, Sep 19, 2019 at 03:27:45PM -0700, mnalajal@xxxxxxxxxxxxxx wrote: > On 2019-09-19 14:58, 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 <mnalajal@xxxxxxxxxxxxxx> > > > > > --- > > > > > 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? > > > > thanks, > > > > greg k-h > > Current soc framework is allowing the soc info drivers to create very > limited > soc information as sysfs entries like machine name, family, revision and > soc_id. > Sometimes it become a limited information for the clients to know more about > soc > information. In this scenario soc info drivers are adding their own sysfs > entries > on top of what soc framework is doing like hw_platform, hw_platform_subtype > etc. > I believe this will be an issue for the other soc vendors as well. It is > good that > if we could add these into the soc framework rather than individual clients > defining > and adding them as per their requirement. It's fine to add sysfs files (as long as you document them in Documentation/ABI/) but don't do so file-by-file in a driver as that is racy and will not work. See 6d03c140db2e ("USB: phy: fsl-usb: convert platform driver to use dev_groups") as an example of how to do this in a simple way to have the driver core do all of the work for you automatically. thanks, greg k-h