On Thu, Aug 06, 2020 at 11:37:38AM +0800, Jason Wang wrote:
>
> On 2020/8/5 下午7:45, Michael S. Tsirkin wrote:
> > > > #define virtio_cread(vdev, structname, member, ptr)
> > > > \
> > > > do {
> > > > \
> > > > might_sleep();
> > > > \
> > > > /* Must match the member's type, and be integer */
> > > > \
> > > > - if (!typecheck(typeof((((structname*)0)->member)),
> > > > *(ptr))) \
> > > > + if (!__virtio_typecheck(structname, member, *(ptr)))
> > > > \
> > > > (*ptr) = 1;
> > > > \
> > > A silly question, compare to using set()/get() directly, what's the value
> > > of the accessors macro here?
> > >
> > > Thanks
> > get/set don't convert to the native endian, I guess that's why
> > drivers use cread/cwrite. It is also nice that there's type
> > safety, checking the correct integer width is used.
>
>
> Yes, but this is simply because a macro is used here, how about just doing
> things similar like virtio_cread_bytes():
>
> static inline void virtio_cread(struct virtio_device *vdev,
> unsigned int offset,
> void *buf, size_t len)
>
>
> And do the endian conversion inside?
>
> Thanks
>
Then you lose type safety. It's very easy to have an le32 field
and try to read it into a u16 by mistake.
These macros are all about preventing bugs: and the whole patchset
is about several bugs sparse found - that is what prompted me to make
type checks more strict.
> >
