Re: [PATCH net-next v2 06/10] net: phy: print an info if a broken C45 bus is found

[Michael Walle]

Am 2023-06-23 22:35, schrieb Simon Horman:
> On Fri, Jun 23, 2023 at 07:42:08PM +0200, Andrew Lunn wrote:
> > On Fri, Jun 23, 2023 at 12:29:15PM +0200, Michael Walle wrote:
> > > If there is an PHY which gets confused by C45 transactions on the MDIO
> > > bus, print an info together with the PHY identifier of the offending
> > > one.
> > >
> > > Signed-off-by: Michael Walle <mwalle@xxxxxxxxxx>
> > >
> > > ---
> > > I wasn't sure if this should be phydev_dbg() or phydev_info(). I mainly
> > > see this as an info to a user why some PHYs might not be probed (or
> > > c45-over-c22 is used later).
> >
> > The information is useful to the DT writer, not the 'user'. I would
> > assume the DT writer has a bit more kernel knowledge and can debug
> > prints on. So i would suggest phydev_dbg().

Why the DT writer? There could be no DT at all, right? But yeah, fair
enough, I thought of our hardware engineers as a user, which might be
surprised to find no C45 transactions at all for a C45 PHY.

That said, I don't have a strong opinion. I'm fine to switch that to
dev_dbg() to make the kernel output less noisy.

> > > @@ -617,10 +617,10 @@ static int mdiobus_scan_bus_c45(struct mii_bus *bus)
> > >   */
> > >  void mdiobus_scan_for_broken_c45_access(struct mii_bus *bus)
> > >  {
> > > +	struct phy_device *phydev;
> > >  	int i;
> > >
> > >  	for (i = 0; i < PHY_MAX_ADDR; i++) {
> > > -		struct phy_device *phydev;
> > >  		u32 oui;
> >
> > It is not clear why you changed the scope of phydev. I guess another
> > version used phydev_info(), where as now you have dev_info()?
>
> I think it is so it can be used in the dev_info() call below.

Yes, to print the PHY ID of the offending one.

> However Smatch has it's doubts that it is always initialised there.
>
>   .../mdio_bus.c:638 mdiobus_scan_for_broken_c45_access() error: we 
> previously assumed 'phydev' could be null (see line 627)
>
> > >  		phydev = mdiobus_get_phy(bus, i);
>
> Line 627 immediately follows the line above, like this:
>
> 		if (!phydev)
> 			continue;

Mhh, I see. bus->prevent_c45_access could (theoretically) set before
calling this function. I could set it to false at the beginning of
this function or I could use a new flag to indicate when to print the
warning. Any suggestions?

-michael