netdev - Re: [PATCH v1 1/2] driver core: fw_devlink: Add support for FWNODE_FLAG_BROKEN

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Date:   Thu, 2 Sep 2021 10:58:29 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Vladimir Oltean <olteanv@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Len Brown <lenb@...nel.org>,
        Alvin Sipraga <ALSI@...g-olufsen.dk>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        linux-acpi@...r.kernel.org
Subject: Re: [PATCH v1 1/2] driver core: fw_devlink: Add support for FWNODE_FLAG_BROKEN_PARENT

On Thu, Sep 2, 2021 at 10:41 AM Andrew Lunn <andrew@...n.ch> wrote:
>
> >   How would this be avoided? Or are you thinking of some kind of two-level
> >   component driver system:
> >   - the DSA switch is a component master, with components being its
> >     sub-devices such as internal PHYs etc
> >   - the DSA switch is also a component of the DSA switch tree
>
> I think you might be missing a level. Think about the automotive
> reference design system you posted the DT for a couple of days
> ago. Don't you have cascaded switches, which are not members of the
> same DSA tree. You might need a component for that whole group of
> switches, above what you suggest here.
>
> Can you nest components? How deep can you nest them?

As far as I know you can nest components.

Also, technically you can make your own lightweight component model
like behaviour using stateful device links or fwnode links (probably
just a simple for loop). Just create a new "dsa_switch_tree" device
and create device links between that and whatever other devices that
need to probe first. And then you'll just have a common
"dsa_switch_tree" driver that probes these types of devices.

I'm waiting for [1] to land before I jump in and clean up the
component model to be more flexible and cleaner by using device links.
The current implementation does a lot of stuff that device links will
take care of for free.

[1] - https://lore.kernel.org/lkml/CAGETcx-mRrqC_sGiBk+wx8RtwjJjXf0KJo+ejU6SweEBiATaLw@mail.gmail.com/

-Saravana