Peter Maydell <peter.mayd...@linaro.org> 于2018年11月13日周二 下午5:49写道：
> On 13 November 2018 at 01:42, Li Qiang <liq...@gmail.com> wrote: > > This can avoid the NULL-deref if the rm doesn't has a > > read/write nor write/read_with_attrs callback. > > > > Signed-off-by: Li Qiang <liq...@gmail.com> > > --- > > memory.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > Alternative approach -- assert that every MemoryRegionOps has > pointers to callbacks in it, when it is registered in > memory_region_init_io() > Actually I have considered this approach, but I rember Paolo remind me that some of this MR without read callback's is valid because the read can never be called, such as 'notdirty_mem_ops'. So I choose add a check here. > and memory_region_init_rom_device_nomigrate(). > > I don't have a strong opinion on which is better, but I guess > I slightly favour requiring devices to be specific about what > their read/write behaviour is. > > Do we have many devices that legitimately only want to implement > one of read and write, not both ? AFAICS, the device has just one read or write is not uncommon. But nearly all of them implement a nop function does nothing. So there just very little lack of the read or write function. Thanks, Li Qiang > > thanks > -- PMM >
