Re: [PATCH v16 6/8] i3c: hub: Add support for the I3C interface in the I3C hub

[Krzysztof Kozlowski <krzk@kernel.org>]

On 26/08/2026 12:38, Lakshay Piplani wrote:
> +/**
> + * i3c_hub_init() - Initialize hub context
> + * @hub: Hub instance
> + * @ops: Vendor callbacks
> + * @hub_dev: I3C hub device
> + */
> +void i3c_hub_init(struct i3c_hub *hub,
> +		  const struct i3c_hub_ops *ops,
> +		  struct i3c_device *hub_dev)
> +{
> +	struct i3c_master_controller *parent;
> +	unsigned int depth;
> +
> +	hub->ops = ops;
> +	hub->hub_dev = hub_dev;
> +	mutex_init(&hub->lock);
> +
> +	if (!IS_ENABLED(CONFIG_LOCKDEP))

So without lockdep you do not initialize? Honestly, kerneldoc is useless
here and explains nothing. Kerneldoc is pretty clear - you initialize
hub context thus why hub context should be uninitialized without lockdep?

> +		return;
> +
> +	if (WARN_ON_ONCE(!hub_dev || !hub_dev->desc))
> +		return;

How is this possible? Why panicking the machine?

> +
> +	parent = i3c_dev_get_master(hub_dev->desc);
> +	if (WARN_ON_ONCE(!parent))
> +		return;

Why panicking here (WARN on panic)?

> +
> +	/*
> +	 * The routing mutex has the same hub nesting depth as the virtual
> +	 * controllers this hub exposes, so the parent controller is one level
> +	 * shallower. Keying it once here, rather than per port, avoids
> +	 * reclassifying the single shared routing mutex from a later port that
> +	 * may already have used it.
> +	 */
> +	depth = i3c_hub_controller_depth(parent) + 1;
> +	if (WARN_ONCE(depth > I3C_HUB_MAX_LOCK_DEPTH,
> +		      "i3c-hub: routing lock depth %u exceeds lockdep support\n",
> +		      depth))


> +		depth = I3C_HUB_MAX_LOCK_DEPTH;
> +
> +	lockdep_set_class(&hub->lock, &i3c_hub_routing_lock_keys[depth - 1]);
> +}
> +EXPORT_SYMBOL_GPL(i3c_hub_init);
> +
> +const struct i3c_master_controller_ops *i3c_hub_master_ops(void)
> +{
> +	return &i3c_hub_master_ops_data;
> +}
> +EXPORT_SYMBOL_GPL(i3c_hub_master_ops);

Do you really need a wrapper call over single variable? Can the i3c hub
core code be NOT present when your I3C hub driver is buillin?


Best regards,
Krzysztof