linux-kernel - Re: [PATCH v1] driver core: fw_devlink: Don't create device links for devices not on a bus

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Message-ID: <CAGETcx9U2M5i1CAx605fG3Qwm1xwjH2uy4kY4vrAF7YSRSSg+w@mail.gmail.com>
Date:   Wed, 1 Sep 2021 17:16:57 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Android Kernel Team <kernel-team@...roid.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] driver core: fw_devlink: Don't create device links for
 devices not on a bus

On Wed, Sep 1, 2021 at 3:17 PM Ulf Hansson <ulf.hansson@...aro.org> wrote:
>
> On Wed, 1 Sept 2021 at 23:54, Saravana Kannan <saravanak@...gle.com> wrote:
> >
> > On Wed, Sep 1, 2021 at 8:45 AM Ulf Hansson <ulf.hansson@...aro.org> wrote:
> > >
> > > On Wed, 1 Sept 2021 at 00:45, Saravana Kannan <saravanak@...gle.com> 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[1] or sync_state() call back issues[2].
> > > >
> > > > [1] - https://lore.kernel.org/lkml/CAGETcx_xJCqOWtwZ9Ee2+0sPGNLM5=F=djtbdYENkAYZa0ynqQ@mail.gmail.com/
> > > > [2] - https://lore.kernel.org/lkml/CAPDyKFo9Bxremkb1dDrr4OcXSpE0keVze94Cm=zrkOVxHHxBmQ@mail.gmail.com/
> > >
> > > Unfortunately, this doesn't fix my problem in [2].
> > >
> > > When the "soctest" device is initialized, via of_platform_populate(),
> > > it will be attached to the platform bus, hence the check for the bus
> > > pointer that you suggest to add below, doesn't have an impact on my
> > > use case. I still get the below in the log:
> >
> > *face palm* Right. I forgot that. I just read "bus" and my mind went
> > to busses added as devices. It apparently also didn't help [1] which
> > is surprising to me. I'll dig into that separately. I'll look into
> > fixing this. The annoying part is that some devices have compatible
> > property that's both "simple-bus" and some other string that a driver
> > actually matches with.
>
> Yes, that is my view of the problem as well.
>
> So perhaps we should do a more fine grained check for when the
> "simple-bus" compatible is present in the node,

Exactly. Do you want to take a stab at this? There are too many things
I want to work on, so if you can do this one, that'd be nice.

> and then don't create
> a fw_devlink if we reach an ascendant with only this compatible?

And you can achieve that by setting this flag for that DT node:
fwnode->flags |= FWNODE_FLAG_NOT_DEVICE;

-Saravana