# Re: \[PATCH net 5/6\] net: stmmac: selftests: Account for the UC filter list for filtering tests

- From: Andrew Lunn \<andrew@lunn.ch\>
- Date: 2026-08-26 18:26:23 
- List: netdev
- Page: https://ratatoskr.run/netdev/2026/08/17466182
- Thread: https://ratatoskr.run/netdev/2026/08/17464948/t.md

```text
On Wed, Aug 26, 2026 at 04:04:57PM +0200, Maxime Chevallier wrote:
> On dwmac, one of the Unicast filter entries is used to store the local
> HW addr. This means that we have to use promisc mode for any kind of
> unicast filtering if we only have one slot in our unicast filter.
> 
> The number of slots available depends on how the IP is integrated, and
> we can't autodiscover how many of these slots we have available, so
> the DT property snps,perfect-filter-entries can be used to specify how
> many are available.
> 
> Most IP variants default to 1 if this isn't specified, which is the case
> for the amlogic variants (in this case, S905X3).

Do you have this hardware? Did you try increasing the DT property to
find out how many slots it actually has?

Maybe a nice little project for a newbie which has some stmmac
hardware. Write some code which adds MAC addresses and reads them back
again. Determine at runtime how many slots there actually are.

> Fixes: 091810dbded9 ("net: stmmac: Introduce selftests support")
> Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew
```