On Mon, Jul 06, 2015 at 11:04:24AM +0100, Peter Maydell wrote: > On 6 July 2015 at 11:03, Michael S. Tsirkin <m...@redhat.com> wrote: > > On Mon, Jul 06, 2015 at 10:11:18AM +0100, Peter Maydell wrote: > >> But address_space_rw() is just the "memcpy bytes to the > >> target's memory" operation -- if you have a pile of bytes > >> then there are no endianness concerns. If you don't have > >> a pile of bytes then you need to know the structure of > >> the data you're DMAing around, and you should probably > >> have a loop doing things with the specify-the-width functions. > > > Absolutely. But what if DMA happens to target another device > > and not memory? Device needs some endian-ness so it needs > > to be converted to that. > > Yes, and address_space_rw() already deals with conversion to > that device's specified endianness. > > -- PMM
Yes, but incorrectly if target endian != host endian. For example, LE target and LE device on BE host. IO callbacks always get a native endian format so they expect to get byte 0 of the buffer in MSB on this host. -- MST
