Re: Component API not right for DSA?

["Russell King (Oracle)" <linux@armlinux.org.uk>]

On Wed, Sep 18, 2024 at 02:10:08PM +0300, Vladimir Oltean wrote:
> This is all great, but then I realized that, for addressing issue #2,
> it is no better than what we currently have. Namely, by default the tree
> looks like this:
> 
...
> 
> but after this operation:
> 
> $ echo d0032004.mdio-mii:11 > /sys/bus/mdio_bus/devices/d0032004.mdio-mii\:11/driver/unbind
> $ cat /sys/kernel/debug/device_component/dsa_tree.0.auto
> aggregate_device name                                  status
> -------------------------------------------------------------
> dsa_tree.0.auto                                     not bound
> 
> device name                                            status
> -------------------------------------------------------------
> (unknown)                                      not registered
> d0032004.mdio-mii:10                                not bound
> d0032004.mdio-mii:12                                not bound
> 
> the tree (component master) is unbound, its unbind() method calls
> component_unbind_all(), and this also unbinds the other switches.

Correct. As author of the component helper... The component helper was
designed for an overall device that is made up of multiple component
devices that are themselves drivers, and _all_ need to be present in
order for the overall device to be functional. It is not intended to
address cases where an overall device has optional components.

The helper was originally written to address that problem for the
Freescale i.MX IPU, which had been sitting in staging for considerable
time, and was blocked from being moved out because of issues with this
that weren't solvable at the time (we didn't have device links back
then, which probably could've been used instead.)

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