On Wed, Aug 11, 2010 at 09:07:27PM +0200, Martin Fuzzey wrote: > Greg KH wrote: > >> So the question is are hcds expected to accept arbitarilly aligned but > >> heap allocated pointers (such as the result of kmalloc() + 1)? > >> > > > > It sounds like your HCD doesn't like this, so perhaps we should make > > that rule :) > > > > If you allocate the urb with a kmalloc() call with no offset, does it > > all work properly? > Yes > > The driver should be calling usb_alloc_urb() which > > does this automatically for them, right? Or is it trying to allocate > > things on its own somehow? > > > > > It's not the URB itself (which is allocated by usb_alloc_urb) but rather > the buffer pointer within the URB that causes the problem. Doh, you are right, sorry about that. > It's the asix driver (or more exactly the usbnet core used by that driver). > It does (rx_submit() in drivers/net/usb/usbnet.c): > > urb = usb_alloc_urb(); > skb = alloc_skb (...); > skb_reserve (skb, NET_IP_ALIGN); > usb_fill_bulk_urb (urb,... skb->data); > usb_submit_urb(urb) > > skb->data as returned by alloc_skb() is aligned > but skb_reserve adds 2. > > Thus removing the skb_reserve() call makes it work. > BUT if I do that the IP header is no longer aligned so accesses further > up the network stack have to be fixed up by exception handlers which is > expensive (even with hcds which don't require this) Can you fix this in the host controller driver? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
