Subject: Re: [PATCH v5 5/6] usb: roles: add USB Type-B GPIO connector driver

From: Heikki Krogerus <[email-masked]>
Date: Mon, 20 May 2019 11:31:51 +0300

On Tue, May 14, 2019 at 04:47:22PM +0800, Chunfeng Yun wrote:
> +static int usb_conn_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *node = dev->of_node;
> +	struct device_node *remote_node;
> +	struct usb_conn_info *info;
> +	int ret = 0;
> +
> +	info = devm_kzalloc(dev, sizeof(*info), GFP_KERNEL);
> +	if (!info)
> +		return -ENOMEM;
> +
> +	info->dev = dev;
> +	info->id_gpiod = devm_gpiod_get_optional(dev, "id", GPIOD_IN);
> +	if (IS_ERR(info->id_gpiod))
> +		return PTR_ERR(info->id_gpiod);
> +
> +	info->vbus_gpiod = devm_gpiod_get_optional(dev, "vbus", GPIOD_IN);
> +	if (IS_ERR(info->vbus_gpiod))
> +		return PTR_ERR(info->vbus_gpiod);
> +
> +	if (!info->id_gpiod && !info->vbus_gpiod) {
> +		dev_err(dev, "failed to get gpios\n");
> +		return -ENODEV;
> +	}
> +
> +	if (info->id_gpiod)
> +		ret = gpiod_set_debounce(info->id_gpiod, USB_GPIO_DEB_US);
> +	if (!ret && info->vbus_gpiod)
> +		ret = gpiod_set_debounce(info->vbus_gpiod, USB_GPIO_DEB_US);
> +	if (ret < 0)
> +		info->debounce_jiffies = msecs_to_jiffies(USB_GPIO_DEB_MS);
> +
> +	INIT_DELAYED_WORK(&info->dw_det, usb_conn_detect_cable);
> +
> +	info->vbus = devm_regulator_get(dev, "vbus");
> +	if (IS_ERR(info->vbus)) {
> +		dev_err(dev, "failed to get vbus\n");
> +		return PTR_ERR(info->vbus);
> +	}
> +
> +	remote_node = of_graph_get_remote_node(node, -1, 0);

This is really not ideal. In practice this code will only work if
there is only one endpoint described for this device, or if the first
endpoint is always the one we are looking for. There is no way to
guarantee that.

The code really has to walk through the entire graph, and identify the
remote endpoint it's looking for (and for that we have the boolean
device property).

> +	if (!remote_node) {
> +		dev_err(dev, "failed to get remote node\n");
> +		return -ENODEV;
> +	}
> +
> +	info->role_sw =
> +		fwnode_usb_role_switch_get(of_fwnode_handle(remote_node));

So fwnode_usb_role_switch_get() needs be the one that walks through
the graph, not the drivers. Otherwise every driver will do the same
exact steps (boilerplate). Here you need to be able to just pass the
node of this device, not the remote endpoint:

        info->role_sw = fwnode_usb_role_switch_get(dev_fwnode(&client->dev));

But why do you need that function at all? Why wouldn't
usb_role_switch_get() work?

        info->role_sw = usb_role_switch_get(&client->dev);

> +	of_node_put(remote_node);
> +	if (IS_ERR(info->role_sw)) {
> +		dev_err(dev, "failed to get role switch\n");
> +		return PTR_ERR(info->role_sw);
> +	}
> +
> +	if (info->id_gpiod) {
> +		info->id_irq = gpiod_to_irq(info->id_gpiod);
> +		if (info->id_irq < 0) {
> +			dev_err(dev, "failed to get ID IRQ\n");
> +			ret = info->id_irq;
> +			goto put_role_sw;
> +		}
> +
> +		ret = devm_request_threaded_irq(dev, info->id_irq, NULL,
> +						usb_conn_isr, USB_CONN_IRQF,
> +						pdev->name, info);
> +		if (ret < 0) {
> +			dev_err(dev, "failed to request ID IRQ\n");
> +			goto put_role_sw;
> +		}
> +	}
> +
> +	if (info->vbus_gpiod) {
> +		info->vbus_irq = gpiod_to_irq(info->vbus_gpiod);
> +		if (info->vbus_irq < 0) {
> +			dev_err(dev, "failed to get VBUS IRQ\n");
> +			ret = info->vbus_irq;
> +			goto put_role_sw;
> +		}
> +
> +		ret = devm_request_threaded_irq(dev, info->vbus_irq, NULL,
> +						usb_conn_isr, USB_CONN_IRQF,
> +						pdev->name, info);
> +		if (ret < 0) {
> +			dev_err(dev, "failed to request VBUS IRQ\n");
> +			goto put_role_sw;
> +		}
> +	}
> +
> +	platform_set_drvdata(pdev, info);
> +
> +	/* Perform initial detection */
> +	usb_conn_queue_dwork(info, 0);
> +
> +	return 0;
> +
> +put_role_sw:
> +	usb_role_switch_put(info->role_sw);
> +	return ret;
> +}

thanks,

-- 
heikki

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