USB: allow some usb functions to take a const pointer.

The functions to_usb_interface(), to_usb_device, and
interface_to_usbdev() sometimes would like to take a const * and return
a const * back.  As we are doing pointer math, a call to container_of()
loses the const-ness of a pointer, so use a _Generic() macro to pick the
proper inline function to call instead.

Link: https://lore.kernel.org/r/20221016104155.1260201-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/usb.h b/include/linux/usb.h
index 9ff1ad4..3a55131 100644 (file)
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -258,7 +258,27 @@ struct usb_interface {
        struct device *usb_dev;
        struct work_struct reset_ws;    /* for resets in atomic context */
 };
-#define        to_usb_interface(d) container_of(d, struct usb_interface, dev)
+
+static inline struct usb_interface *__to_usb_interface(struct device *d)
+{
+       return container_of(d, struct usb_interface, dev);
+}
+
+static inline const struct usb_interface *__to_usb_interface_const(const struct device *d)
+{
+       return container_of(d, struct usb_interface, dev);
+}
+
+/*
+ * container_of() will happily take a const * and spit back a non-const * as it
+ * is just doing pointer math.  But we want to be a bit more careful in the USB
+ * driver code, so manually force any const * of a device to also be a const *
+ * to a usb_device.
+ */
+#define to_usb_interface(dev)                                          \
+       _Generic((dev),                                                 \
+                const struct device *: __to_usb_interface_const,       \
+                struct device *: __to_usb_interface)(dev)
 
 static inline void *usb_get_intfdata(struct usb_interface *intf)
 {
@@ -709,12 +729,41 @@ struct usb_device {
        u16 hub_delay;
        unsigned use_generic_driver:1;
 };
-#define        to_usb_device(d) container_of(d, struct usb_device, dev)
 
-static inline struct usb_device *interface_to_usbdev(struct usb_interface *intf)
+static inline struct usb_device *__to_usb_device(struct device *d)
+{
+       return container_of(d, struct usb_device, dev);
+}
+
+static inline const struct usb_device *__to_usb_device_const(const struct device *d)
+{
+       return container_of(d, struct usb_device, dev);
+}
+
+/*
+ * container_of() will happily take a const * and spit back a non-const * as it
+ * is just doing pointer math.  But we want to be a bit more careful in the USB
+ * driver code, so manually force any const * of a device to also be a const *
+ * to a usb_device.
+ */
+#define to_usb_device(dev)                                     \
+       _Generic((dev),                                         \
+                const struct device *: __to_usb_device_const,  \
+                struct device *: __to_usb_device)(dev)
+
+static inline struct usb_device *__intf_to_usbdev(struct usb_interface *intf)
 {
        return to_usb_device(intf->dev.parent);
 }
+static inline const struct usb_device *__intf_to_usbdev_const(const struct usb_interface *intf)
+{
+       return to_usb_device((const struct device *)intf->dev.parent);
+}
+
+#define interface_to_usbdev(intf)                                      \
+       _Generic((intf),                                                \
+                const struct usb_interface *: __intf_to_usbdev_const,  \
+                struct usb_interface *: __intf_to_usbdev)(intf)
 
 extern struct usb_device *usb_get_dev(struct usb_device *dev);
 extern void usb_put_dev(struct usb_device *dev);