On Saturday 08 November 2008, Nicolas Pitre wrote: > The ARM processor traditionally cannot access misaligned short and int > values in memory. By using the packed attribute you tell the compiler > that the structure should not have inserted padding to align its > members, and that accesses are to be performed wth byte accesses and the > value reconstructed that way. ... but then when you pass "&misaligned_ptr->member" to some other function, that other function generally won't know it needs to use byte access. So, be careful. The "packed" struct attribute isn't a panacea. General Linux kernel policy is to use <asm/unaligned.h> accessors, but obviously "packed" has advantages when you've got to pull structures out of protocol buffers. The userspace headers don't seem to support such accessors though. Also, the network stack is known for making assumptions about its data being properly aligned. See how NET_IP_ALIGN is used inside the kernel; you might be happier aligning your RX buffers before reading data into them from the kernel. - Dave -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
