linux-kernel - [PATCH] usb: core: support interface node for simple USB devices

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Message-Id: <20250122134732.2318554-1-catalin.popescu@leica-geosystems.com>
Date: Wed, 22 Jan 2025 14:47:32 +0100
From: Catalin Popescu <catalin.popescu@...ca-geosystems.com>
To: gregkh@...uxfoundation.org,
	johan@...nel.org
Cc: linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	m.felsch@...gutronix.de,
	bsp-development.geo@...ca-geosystems.com,
	Catalin Popescu <catalin.popescu@...ca-geosystems.com>
Subject: [PATCH] usb: core: support interface node for simple USB devices

A simple usb device has a single configuration and a single interface
and is considered as a "combined node" when defined in the devicetree.
If available, its interface node is simply ignored which is a problem
whenever the interface node has subnodes. To prevent that from happening
first check for any subnode and ignore the interface node only if no
subnode was found.

Example: FTDI chip FT234XD that has only one UART interface which is
being used as a serdev by other driver.

device@1 {
	compatible = "usb403,6015";
	reg = <1>;

	#address-cells = <2>;
	#size-cells = <0>;

	interface@0 {
		compatible = "usbif403,6015.config1.0";
		reg = <0 1>;

		bluetooth {
			compatible = "nxp,88w8987-bt";
		};
	};
};

Signed-off-by: Catalin Popescu <catalin.popescu@...ca-geosystems.com>
---
 drivers/usb/core/message.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index d2b2787be409..f4a9d1831f6a 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -2102,6 +2102,7 @@ int usb_set_configuration(struct usb_device *dev, int configuration)
 		struct usb_interface_cache *intfc;
 		struct usb_interface *intf;
 		struct usb_host_interface *alt;
+		struct device_node *np;
 		u8 ifnum;
 
 		cp->interface[i] = intf = new_interfaces[i];
@@ -2126,12 +2127,11 @@ int usb_set_configuration(struct usb_device *dev, int configuration)
 		intf->cur_altsetting = alt;
 		usb_enable_interface(dev, intf, true);
 		intf->dev.parent = &dev->dev;
-		if (usb_of_has_combined_node(dev)) {
+		np = usb_of_get_interface_node(dev, configuration, ifnum);
+		if (!of_get_child_count(np) && usb_of_has_combined_node(dev))
 			device_set_of_node_from_dev(&intf->dev, &dev->dev);
-		} else {
-			intf->dev.of_node = usb_of_get_interface_node(dev,
-					configuration, ifnum);
-		}
+		else
+			intf->dev.of_node = np;
 		ACPI_COMPANION_SET(&intf->dev, ACPI_COMPANION(&dev->dev));
 		intf->dev.driver = NULL;
 		intf->dev.bus = &usb_bus_type;

base-commit: f066b5a6c7a06adfb666b7652cc99b4ff264f4ed
-- 
2.34.1