USB: <linux/usb/ch9.h> minor doc update

Minor doc update to <linux/usb/ch9.h> ... say where USB_DT_CS_* came
from and update the definitions to match how they're derived there.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 9 insertions, 6 deletions

diff --git a/include/linux/usb/ch9.h b/include/linux/usb/ch9.h
index 1122a6c2c1a3..6169438ec5a2 100644
--- a/include/linux/usb/ch9.h
+++ b/include/linux/usb/ch9.h
@@ -181,12 +181,15 @@ struct usb_ctrlrequest {
 #define USB_DT_WIRE_ADAPTER             0x21
 #define USB_DT_RPIPE                    0x22
 
-/* conventional codes for class-specific descriptors */
-#define USB_DT_CS_DEVICE                0x21
-#define USB_DT_CS_CONFIG                0x22
-#define USB_DT_CS_STRING                0x23
-#define USB_DT_CS_INTERFACE             0x24
-#define USB_DT_CS_ENDPOINT              0x25
+/* Conventional codes for class-specific descriptors.  The convention is
+ * defined in the USB "Common Class" Spec (3.11).  Individual class specs
+ * are authoritative for their usage, not the "common class" writeup.
+ */
+#define USB_DT_CS_DEVICE                (USB_TYPE_CLASS | USB_DT_DEVICE)
+#define USB_DT_CS_CONFIG                (USB_TYPE_CLASS | USB_DT_CONFIG)
+#define USB_DT_CS_STRING                (USB_TYPE_CLASS | USB_DT_STRING)
+#define USB_DT_CS_INTERFACE             (USB_TYPE_CLASS | USB_DT_INTERFACE)
+#define USB_DT_CS_ENDPOINT              (USB_TYPE_CLASS | USB_DT_ENDPOINT)
 
 /* All standard descriptors have these 2 fields at the beginning */
 struct usb_descriptor_header {