Re: [PATCH] net: dsa: Fix conditional handling of Wake-on-Lan configuration in dsa_user_set_wol

From: Russell King (Oracle)
Date: Mon Oct 07 2024 - 04:56:52 EST


On Sun, Oct 06, 2024 at 09:57:26PM +0200, Andrew Lunn wrote:
> On Sun, Oct 06, 2024 at 09:40:32PM +0530, Mohammed Anees wrote:
> > Considering the insight you've provided, I've written the code below
> >
> > static int dsa_user_set_wol(struct net_device *dev, struct ethtool_wolinfo *w)
> > {
> > struct dsa_port *dp = dsa_user_to_port(dev);
> > struct dsa_switch *ds = dp->ds;
> > int ret;
> >
> > ret = phylink_ethtool_set_wol(dp->pl, w);
> >
> > if (ret != -EOPNOTSUPP)
> > return ret;
> >
> > if (ds->ops->set_wol)
> > ret = ds->ops->set_wol(ds, dp->index, w);
> > if (ret != -EOPNOTSUPP)
> > return ret;
>
> This can be simplified to just:
>
> > if (ds->ops->set_wol)
> > return ds->ops->set_wol(ds, dp->index, w);
> >
> > return -EOPNOTSUPP;
> > }

I don't think the above is correct. While the simplification is, the
overall logic is not.

Let's go back to what Andrew said in his previous reply:

"So userspace could say pumbagsf, with the PHY supporting pmub and the
MAC supporting agsf, and the two need to cooperate."

The above does not do this. Let's go back further:

phylink_ethtool_set_wol(dp->pl, w);

if (ds->ops->set_wol)
ret = ds->ops->set_wol(ds, dp->index, w);

The original code _does_ do this, allowing the PHY and MAC to set
their modes, although the return code is not correct.

I notice V2 of the patch has been posted - in my opinion prematurely
because there's clearly the discussion on the first version has not
reached a conclusion yet.

What I would propose is the following:

int phy_ret, mac_ret;

phy_ret = phylink_ethtool_set_wol(dp->pl, w);
if (phy_ret != 0 && phy_ret != -EOPNOTSUPP)
return phy_ret;

if (ds->ops->set_wol)
mac_ret = ds->ops->set_wol(ds, dp->index, w);
else
mac_ret = -EOPNOTSUPP;

if (mac_ret != 0 && mac_ret != -EOPNOTSUPP)
return mac_ret;

/* Combine the two return codes. If either returned zero,
* then we have been successful.
*/
if (phy_ret == 0 || mac_ret == 0)
return 0;

return -EOPNOTSUPP;

Which I think is the closest one can get to - there is the possibility
for phylink_ethtool_set_wol() to have modified the WoL state, but
ds->ops->set_wol() to fail with an error code, causing this to return
failure, but I don't see that as being avoidable without yet more
complexity.

--
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