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 <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? > > > > > > > > > > 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