Re: [PATCH v1] driver core: fw_devlink: Don't create device links for devices not on a bus
From: Saravana Kannan
Date: Wed Sep 01 2021 - 02:58:25 EST
On Tue, Aug 31, 2021 at 11:24 PM Greg Kroah-Hartman
> On Tue, Aug 31, 2021 at 03:45:10PM -0700, Saravana Kannan wrote:
> > Devices that are not on a bus will never have a driver bound to it. So,
> > fw_devlink should not create device links for it as it can cause probe
> > issues or sync_state() call back issues.
> >  - https://lore.kernel.org/lkml/CAGETcx_xJCqOWtwZ9Ee2+0sPGNLM5=F=djtbdYENkAYZa0ynqQ@xxxxxxxxxxxxxx/
> >  - https://lore.kernel.org/lkml/CAPDyKFo9Bxremkb1dDrr4OcXSpE0keVze94Cm=zrkOVxHHxBmQ@xxxxxxxxxxxxxx/
> > Fixes: f9aa460672c9 ("driver core: Refactor fw_devlink feature")
> > Reported-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> > Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> > Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx>
> > ---
> > drivers/base/core.c | 16 ++++++++++++++++
> > 1 file changed, 16 insertions(+)
> > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > index f6360490a4a3..304a06314656 100644
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -1719,8 +1719,24 @@ static int fw_devlink_create_devlink(struct device *con,
> > struct device *sup_dev;
> > int ret = 0;
> > + /*
> > + * If a consumer device is not on a bus (i.e. a driver will never bind
> > + * to it), it doesn't make sense for fw_devlink to create device links
> > + * for it.
> > + */
> > + if (con->bus == NULL)
> > + return -EINVAL;
> > +
> Why would a device not be on a bus that has to do with a driver needing
> it? What types of devices are these?
I'm not sure what you are asking, because it seems like a question
you'd know the answer to. What I'm trying to say is that
bus_probe_device() is obviously only possible if the device is on a
bus. And fw_devlink creates managed device links that track if a
device is bound to a driver. So it doesn't make sense to create the
device link if the device is not on a bus.
There are plenty of examples for this -- like all the devices that get
added to a class? For example the platform bus or the mdio bus itself
are devices that are added to a class instead of a bus.
Not sure if I answered your question. Let me know.