linux-kernel - Re: [PATCH 2/3] driver core: Introduce fw_devlink_relax

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Message-ID: <CAGETcx9F3+9Pw0eYUNC_08yLdVAWuPk-gCnLMtqNKTPwshtnkg@mail.gmail.com>
Date: Thu, 14 Aug 2025 10:54:06 -0700
From: Saravana Kannan <saravanak@...gle.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: Wang Wensheng <wangwensheng4@...wei.com>, rafael@...nel.org, dakr@...nel.org, 
	tglx@...utronix.de, robh@...nel.org, broonie@...nel.org, 
	linux-kernel@...r.kernel.org, chenjun102@...wei.com
Subject: Re: [PATCH 2/3] driver core: Introduce fw_devlink_relax_consumers helper

On Thu, Aug 14, 2025 at 4:39 AM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Thu, Aug 14, 2025 at 07:10:22PM +0800, Wang Wensheng wrote:
> > Some devices are added during its parent's probe and will never get
> > bound to a driver.

Hi Wang,

I'm guessing you are adding these "will never probe" devices to a bus?
Why are you adding devices to a bus if you'll never probe them? You
should use a "class" if these are devices of a type and don't need to
be probed.

> > In this case, with fw_devlink set to "rpm",
> > which is the default value, its consumers will be deferred probe
> > until deferred_probe_timeout when fw_devlink_drivers_done() would
> > relax the devlinks to the suplier.
> >
> > Use this function to relax the consumer devlinks, just like what we
> > do for the unmatched devices in fw_devlink_drivers_done(), so that
> > the consumer devices would be probed not that later.

This function is not meant for use outside fw_devlink core code.

Write a stub driver or move those devices to a class.

> >
> > Signed-off-by: Wang Wensheng <wangwensheng4@...wei.com>
> > ---
> >  drivers/base/core.c    | 22 ++++++++++++++++++++++
> >  include/linux/device.h |  1 +
> >  2 files changed, 23 insertions(+)
> >
> > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > index d22d6b23e758..2f7101ad9d11 100644
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -1754,6 +1754,28 @@ static void fw_devlink_relax_link(struct device_link *link)
> >               dev_name(link->supplier));
> >  }
> >
> > +/**
> > + * fw_devlink_relax_consumers - Relax the devlinks with all its consumers
> > + * @dev: Device whose consumer devlinks will be relaxed
> > + *
> > + * Some devices are added during its parent's probe and will never get bound
> > + * to a driver. In this case its consumers will be deferred probe until
> > + * deferred_probe_timeout.
> > + *
> > + * Use this function to relax the consumer devlinks so that the consumers
> > + * device would be probed not that later.
> > + */
> > +void fw_devlink_relax_consumers(struct device *dev)
> > +{
> > +     struct device_link *link;
> > +
> > +     device_links_write_lock();
> > +     list_for_each_entry(link, &dev->links.consumers, s_node)
> > +             fw_devlink_relax_link(link);
> > +     device_links_write_unlock();
> > +}
> > +EXPORT_SYMBOL_GPL(fw_devlink_relax_consumers);
>
> We currently do not export any "fw_" functions from the driver core, why
> do that now?  This feels wrong as this should all be "internal" to the
> driver core, no driver should be calling this.

Yup, you are right. Definite NACK.

-Saravana