On Wed, Aug 11, 2010 at 5:04 PM, Greg KH <greg@xxxxxxxxx> wrote: >> Here is a pointer to the thread where it was stated that HCD's don't >> have to handle this. >> >> http://kerneltrap.org/mailarchive/linux-usb/2009/4/20/5528164 > > No, that thread is about stack vs. heap allocations, not about alignment > issues. > Well although the issue discussed in that thread was caused by a stack allocation isn't the issue here the same? My understanding is that a heap allocation as returned by kmalloc() will be: 1) correctly aligned for DMA and 2) in a memory zone accessible to DMA whereas a stack allocation is not guaranteed to have either of these properties. The problem I described in that thread was due to case 1 (misalignment) rather than the stack memory zone not being accessible at all to DMA. To which was the reply was basically "use a heap allocation". So the question is are hcds expected to accept arbitarilly aligned but heap allocated pointers (such as the result of kmalloc() + 1)? regards, Martin > 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
