Re: [RFC PATCH 06/10] usb: xhci: Add Tegra XHCI host-controller driver

[Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>]

On Wednesday 14 May 2014 17:33:02 Andrew Bresticker wrote:
> +
> +int tegra_xhci_register_mbox_notifier(struct notifier_block *nb)
> +{
> +	int ret;
> +
> +	mutex_lock(&tegra_xhci_mbox_lock);
> +	ret = raw_notifier_chain_register(&tegra_xhci_mbox_notifiers, nb);
> +	mutex_unlock(&tegra_xhci_mbox_lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(tegra_xhci_register_mbox_notifier);
> +
> +void tegra_xhci_unregister_mbox_notifier(struct notifier_block *nb)
> +{
> +	mutex_lock(&tegra_xhci_mbox_lock);
> +	raw_notifier_chain_unregister(&tegra_xhci_mbox_notifiers, nb);
> +	mutex_unlock(&tegra_xhci_mbox_lock);
> +}
> +EXPORT_SYMBOL(tegra_xhci_unregister_mbox_notifier);

What driver would use these?

My feeling is that if you have a mailbox that is used by multiple
drivers, you should use a proper mailbox driver to operate them,
and have the drivers register with that API instead of a custom one.

> +	/* Create child xhci-plat device */
> +	memset(xhci_resources, 0, sizeof(xhci_resources));
> +	res = platform_get_resource(to_platform_device(dev), IORESOURCE_IRQ, 0);
> +	if (!res) {
> +		dev_err(dev, "Missing XHCI IRQ\n");
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +	xhci_resources[0].start = res->start;
> +	xhci_resources[0].end = res->end;
> +	xhci_resources[0].flags = res->flags;
> +	xhci_resources[0].name = res->name;
> +	res = platform_get_resource(to_platform_device(dev), IORESOURCE_MEM, 0);
> +	if (!res) {
> +		dev_err(dev, "Missing XHCI registers\n");
> +		ret = -ENODEV;
> +		goto out;
> +	}
> +	xhci_resources[1].start = res->start;
> +	xhci_resources[1].end = res->end;
> +	xhci_resources[1].flags = res->flags;
> +	xhci_resources[1].name = res->name;
> +
> +	xhci = platform_device_alloc("xhci-hcd", PLATFORM_DEVID_AUTO);
> +	if (!xhci) {
> +		dev_err(dev, "Failed to allocate XHCI host\n");
> +		ret = -ENOMEM;
> +		goto out;
> +	}

This does not feel appropriate at all: Rather than creating a child device,
you should have a specific driver that hooks into functions exported
by the xhci core. See Documentation/driver-model/design-patterns.txt

	Arnd