Patchwork [U-Boot] usb: align usb_endpoint_descriptor to 16-bit boundary

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Submitter Stefan Kristiansson
Date Oct. 20, 2011, 7:25 p.m.
Message ID <1319138737-10443-1-git-send-email-stefan.kristiansson@saunalahti.fi>
Download mbox | patch
Permalink /patch/120867/
State Accepted
Headers show

Comments

Stefan Kristiansson - Oct. 20, 2011, 7:25 p.m.
The usb_endpoint_descriptor struct is 7 bytes large and is
defined as an array (ep_desc[USB_MAXENDPOINTS])
in the usb_interface struct in include/usb.h

This fact will result in that every odd index in that
array will start at an uneven address, this in
turn makes accesses to u16 wMaxPacketSize unaligned.
Such accesses are illegal on the OpenRISC architecture
(as well as other architectures) and will render a bus error.

Setting the aligned(2) attribute on usb_endpoint_descriptor
will force wMaxPacketSize to a 16-bit boundary.

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
---
 include/usbdescriptors.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
Remy Bohmer - Nov. 26, 2011, 10:33 p.m.
Hi,

2011/10/20 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>:
> The usb_endpoint_descriptor struct is 7 bytes large and is
> defined as an array (ep_desc[USB_MAXENDPOINTS])
> in the usb_interface struct in include/usb.h
>
> This fact will result in that every odd index in that
> array will start at an uneven address, this in
> turn makes accesses to u16 wMaxPacketSize unaligned.
> Such accesses are illegal on the OpenRISC architecture
> (as well as other architectures) and will render a bus error.
>
> Setting the aligned(2) attribute on usb_endpoint_descriptor
> will force wMaxPacketSize to a 16-bit boundary.
>
> Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>

Applied to u-boot-usb.

Kind regards,

Remy

Patch

diff --git a/include/usbdescriptors.h b/include/usbdescriptors.h
index 2dec3b9..392fcf5 100644
--- a/include/usbdescriptors.h
+++ b/include/usbdescriptors.h
@@ -199,7 +199,7 @@  struct usb_endpoint_descriptor {
 	u8 bmAttributes;
 	u16 wMaxPacketSize;
 	u8 bInterval;
-} __attribute__ ((packed));
+} __attribute__ ((packed)) __attribute__ ((aligned(2)));
 
 struct usb_interface_descriptor {
 	u8 bLength;