On Thu, 23 Jul 2026 16:58:14 -0700 Bobby Eshleman wrote:
> > > + if (info->attrs[NETDEV_A_DMABUF_RX_BUF_SIZE]) {
> > > + u32 rx_buf_size =
> > > nla_get_u32(info->attrs[NETDEV_A_DMABUF_RX_BUF_SIZE]);
> > > +
> > > + if (!rx_buf_size || !is_power_of_2(rx_buf_size) ||
> > > + rx_buf_size < PAGE_SIZE) {
> >
> > we should add a check: min: page-size in the Netlink policy?
>
> I played around with this adding:
>
> Documentation/netlink/specs/netdev.yaml:
> definitions:
> + -
> + type: const
> + name: page-size
> + value: 4096 # dummy value, to pass ynl_gen_c.py checks
> + header: asm/page.h
> + scope: kernel
>
> Generating:
>
> +static const struct netlink_range_validation
> netdev_a_dmabuf_rx_page_size_range = {
> + .min = PAGE_SIZE,
> + .max = U32_MAX,
> +};
> +
>
> ... but the dummy 4096 is kind of annoying. ynl_gen_c.py can't know the
> value of PAGE_SIZE but needs some value for its arithmetic checks (e.g.,
> confirm min < max is true).
>
> Should we stick with using a dummy value, or should we add a patch
> teaching ynl_gen_c.py to allow value-less consts (skip the arithmetic
> checks)?
Let's stick to a dummy one for now, but maybe something obviously dummy
like 0 ?
BTW did you add both min and max checks? Cause the only risk with using
a dummy value would be that the policy will be rendered inline, and
inline policy is u16 so 64k wouldn't fit. But your sample above has a
max of u32_max which forces the out-of-line policy, which is what we
want.
