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.