Re: [PATCH net-next v3 02/11] net: phy: introduce phy_has_c45_registers()

[Andrew Lunn]

On Wed, Aug 02, 2023 at 06:10:27PM +0100, Russell King (Oracle) wrote:
> On Wed, Aug 02, 2023 at 06:15:19PM +0200, Andrew Lunn wrote:
> > > I'm confused now. Andrew suggested to split it into four different
> > > functions:
> > > 
> > > phy_has_c22_registers()
> > > phy_has_c45_registers()
> > > phy_has_c22_transfers()
> > > phy_has_c45_transfers()
> > > 
> > > Without a functional change. That is, either return phydev->is_c45
> > > or the inverse.
> > 
> > Without a functional change at this step of introducing the four
> > functions. Then later really implement them to do what the name
> > implies. Doing it in steps helps with bisect when it breaks something.
> > 
> > It could also be that not all four are needed, or not all four are
> > possible. But the four express the full combinations of transfers and
> > registers.
> 
> I'm left wondering how you think that phy_has_c45_registers() can
> be implemented in a useful way, because I'm at a total loss...

get_phy_c22_id() looks at the ID registers, and see if its mostly
Fs. If so, it says -ENODEV. So phy_has_c22_registers() could be
get_phy_c22_id() != -ENODEV. And you can extend that with the logic
you quoted from the standard. get_phy_c45_ids() also returns -ENODEV
if there are no devices in the package. So phy_has_c45_registers()
could be get_phy_c45_id() != -ENODEV.

This is heuristics, not something explicitly from the standard, but
the basic idea of looking for not mostly Fs has been used for a long
time.

    Andrew