USB: descriptor handling
Hi,
I found a bug when working with the u-boot USB subsystem on IXP425 processor
(big endian Xscale aka ARMv5).
I recognized that the second usb_endpoint_descriptor of the attached memory
stick was corrupted.
The reason for this are the packed structures below (either u-boot and
u-boot-usb):
--------------
/* Endpoint descriptor */
struct usb_endpoint_descriptor {
unsigned char bLength;
unsigned char bDescriptorType;
unsigned char bEndpointAddress;
unsigned char bmAttributes;
unsigned short wMaxPacketSize;
unsigned char bInterval;
unsigned char bRefresh;
unsigned char bSynchAddress;
} __attribute__ ((packed));
/* Interface descriptor */
struct usb_interface_descriptor {
unsigned char bLength;
unsigned char bDescriptorType;
unsigned char bInterfaceNumber;
unsigned char bAlternateSetting;
unsigned char bNumEndpoints;
unsigned char bInterfaceClass;
unsigned char bInterfaceSubClass;
unsigned char bInterfaceProtocol;
unsigned char iInterface;
unsigned char no_of_ep;
unsigned char num_altsetting;
unsigned char act_altsetting;
struct usb_endpoint_descriptor ep_desc[USB_MAXENDPOINTS];
} __attribute__ ((packed));
------------
As usb_endpoint_descriptor is only 7byte in length, the start of all
odd ep_desc[] structures is not word aligned. This makes wMaxPacketSize
of these structures also not word aligned.
ARMv5 Architecture however does not support non-aligned multibyte
data type (see A2.8 of ARM Architecture Reference Manual).
Signed-off-by: Stefan Althoefer <stefan.althoefer@web.de>
Signed-off-by: Remy Böhmer <linux@bohmer.net>
diff --git a/include/usb.h b/include/usb.h
index 84a77b2..510df95 100644
--- a/include/usb.h
+++ b/include/usb.h
@@ -91,7 +91,7 @@
unsigned char bInterval;
unsigned char bRefresh;
unsigned char bSynchAddress;
-} __attribute__ ((packed));
+} __attribute__ ((packed)) __attribute__ ((aligned(2)));
/* Interface descriptor */
struct usb_interface_descriptor {