1 files changed, 40 insertions, 0 deletions
diff --git a/drivers/usb/storage/uas-detect.h b/drivers/usb/storage/uas-detect.h
new file mode 100644
index 000000000000..28101c7e6a9f
--- /dev/null
+++ b/drivers/usb/storage/uas-detect.h
@@ -0,0 +1,40 @@
+#include <linux/usb.h>
+#include <linux/usb/hcd.h>
+
+static int uas_is_interface(struct usb_host_interface *intf)
+{
+	return (intf->desc.bInterfaceClass == USB_CLASS_MASS_STORAGE &&
+		intf->desc.bInterfaceSubClass == USB_SC_SCSI &&
+		intf->desc.bInterfaceProtocol == USB_PR_UAS);
+}
+
+static int uas_isnt_supported(struct usb_device *udev)
+{
+	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
+
+	dev_warn(&udev->dev, "The driver for the USB controller %s does not "
+			"support scatter-gather which is\n",
+			hcd->driver->description);
+	dev_warn(&udev->dev, "required by the UAS driver. Please try an"
+			"alternative USB controller if you wish to use UAS.\n");
+	return -ENODEV;
+}
+
+static int uas_find_uas_alt_setting(struct usb_interface *intf)
+{
+	int i;
+	struct usb_device *udev = interface_to_usbdev(intf);
+	int sg_supported = udev->bus->sg_tablesize != 0;
+
+	for (i = 0; i < intf->num_altsetting; i++) {
+		struct usb_host_interface *alt = &intf->altsetting[i];
+
+		if (uas_is_interface(alt)) {
+			if (!sg_supported)
+				return uas_isnt_supported(udev);
+			return alt->desc.bAlternateSetting;
+		}
+	}
+
+	return -ENODEV;
+}