[PATCH v3] usb: core: verify devicetree nodes for USB devices

[Marek Szyprowski]

Commit 69bec7259853 ("USB: core: let USB device know device node")
added support for attaching devicetree node for USB devices. The mentioned
commit however identifies the given USB device node only by the 'reg'
property in the host controller children nodes. The USB device node
however also has to have a 'compatible' property as described in
Documentation/devicetree/bindings/usb/usb-device.txt. Lack for the
'compatible' property check might result in assigning a devicetree node,
which is not intended to be the proper node for the given USB device.

This is important especially when USB host controller has child-nodes for
other purposes. For example, Exynos EHCI and OHCI drivers already define
child-nodes for each physical root hub port and assigns respective PHY
controller and parameters for them. Those binding predates support for
USB devicetree nodes.

Checking for the proper compatibility string allows to mitigate the
conflict between USB device devicetree nodes and the bindings for USB
controllers with child nodes. It also fixes the side-effect of the other
commits, like 01fdf179f4b0 ("usb: core: skip interfaces disabled in
devicetree"), which incorrectly disables some devices on Exynos based
boards.

Reported-by: Markus Reichl <m.reichl@xxxxxxxxxxxxx>
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
v3:
- replaced ad hoc checks by proper test for proper value of the
  compatible string in drivers/usb/core/of.c
v2: https://lkml.org/lkml/2019/5/8/321
v1: https://lkml.org/lkml/2019/5/7/715
---
 drivers/usb/core/hub.c |  3 +++
 drivers/usb/core/of.c  | 31 +++++++++++++++++++++++++++++++
 include/linux/usb/of.h |  2 ++
 3 files changed, 36 insertions(+)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 2f94568ba385..6f2438522d09 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -22,6 +22,7 @@
 #include <linux/usb.h>
 #include <linux/usbdevice_fs.h>
 #include <linux/usb/hcd.h>
+#include <linux/usb/of.h>
 #include <linux/usb/otg.h>
 #include <linux/usb/quirks.h>
 #include <linux/workqueue.h>
@@ -5023,6 +5024,8 @@ static void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,
 		if (status < 0)
 			goto loop;
 
+		usb_of_validate_device_node(udev);
+
 		if (udev->quirks & USB_QUIRK_DELAY_INIT)
 			msleep(2000);
 
diff --git a/drivers/usb/core/of.c b/drivers/usb/core/of.c
index 651708d8c908..2b6f16753edc 100644
--- a/drivers/usb/core/of.c
+++ b/drivers/usb/core/of.c
@@ -30,6 +30,12 @@ struct device_node *usb_of_get_device_node(struct usb_device *hub, int port1)
 	for_each_child_of_node(hub->dev.of_node, node) {
 		if (of_property_read_u32(node, "reg", &reg))
 			continue;
+		/*
+		 * idVendor and idProduct are not yet known, so check only
+		 * a presence of the compatible property.
+		 */
+		if (!of_find_property(node, "compatible", NULL))
+			continue;
 
 		if (reg == port1)
 			return node;
@@ -39,6 +45,31 @@ struct device_node *usb_of_get_device_node(struct usb_device *hub, int port1)
 }
 EXPORT_SYMBOL_GPL(usb_of_get_device_node);
 
+/**
+ * usb_of_validate_device_node() - validate dt node of the probed USB device
+ * @udev: USB device
+ *
+ * Validate devicetree node for the USB device. Compatible string must match
+ * device's idVendor and idProduct, otherwise the of_node will be put and set
+ * to NULL.
+ */
+void usb_of_validate_device_node(struct usb_device *udev)
+{
+	char compatible[13];
+
+	if (!udev->dev.of_node)
+		return;
+
+	snprintf(compatible, sizeof(compatible), "usb%x,%x",
+		 le16_to_cpu(udev->descriptor.idVendor),
+		 le16_to_cpu(udev->descriptor.idProduct));
+
+	if (of_device_is_compatible(udev->dev.of_node, compatible) == 0) {
+		of_node_put(udev->dev.of_node);
+		udev->dev.of_node = NULL;
+	}
+}
+
 /**
  * usb_of_has_combined_node() - determine whether a device has a combined node
  * @udev: USB device
diff --git a/include/linux/usb/of.h b/include/linux/usb/of.h
index dba55ccb9b53..9969efda03ad 100644
--- a/include/linux/usb/of.h
+++ b/include/linux/usb/of.h
@@ -24,6 +24,7 @@ bool usb_of_has_combined_node(struct usb_device *udev);
 struct device_node *usb_of_get_interface_node(struct usb_device *udev,
 		u8 config, u8 ifnum);
 struct device *usb_of_get_companion_dev(struct device *dev);
+void usb_of_validate_device_node(struct usb_device *udev);
 #else
 static inline enum usb_dr_mode
 of_usb_get_dr_mode_by_phy(struct device_node *np, int arg0)
@@ -57,6 +58,7 @@ static inline struct device *usb_of_get_companion_dev(struct device *dev)
 {
 	return NULL;
 }
+static inline void usb_of_validate_device_node(struct usb_device *udev) { }
 #endif
 
 #if IS_ENABLED(CONFIG_OF) && IS_ENABLED(CONFIG_USB_SUPPORT)
-- 
2.17.1