On Wednesday 27 April 2016 23:09:37 Sergei Shtylyov wrote:
> Hello.
>
> On 04/27/2016 10:49 PM, Andrew Lunn wrote:
>
> >> Sergei Shtylyov <sergei.shtyl...@cogentembedded.com> writes:
> >>
> >>> Arnd Bergmann asked that get_phy_device() returns either NULL or the error
> >>> value, not both on error. Do as he said, return ERR_PTR(-ENODEV) instead
> >>> of NULL when the PHY ID registers read as all ones.
> >>>
> >>> Suggested-by: Arnd Bergmann <a...@arndb.de>
> >>> Signed-off-by: Sergei Shtylyov <sergei.shtyl...@cogentembedded.com>
> >>>
> >>> ---
> >>> drivers/net/phy/phy_device.c | 2 +-
> >>> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> Index: net-next/drivers/net/phy/phy_device.c
> >>> ===================================================================
> >>> --- net-next.orig/drivers/net/phy/phy_device.c
> >>> +++ net-next/drivers/net/phy/phy_device.c
> >>> @@ -529,7 +529,7 @@ struct phy_device *get_phy_device(struct
> >>>
> >>> /* If the phy_id is mostly Fs, there is no device there */
> >>> if ((phy_id & 0x1fffffff) == 0x1fffffff)
> >>> - return NULL;
> >>> + return ERR_PTR(-ENODEV);
> >>>
> >>> return phy_device_create(bus, addr, phy_id, is_c45, &c45_ids);
> >>> }
> >
> > This change is wrong, it needs reverting, or the call sights need
> > fixing to expect ENODEV.
>
> So this function had a good reason to return NULL, as it turned out... :-(
>
> > The point is, the device not being there is not an error, with respect
> > to the code calling this function.
> >
> > It gets called by mdiobus_scan()
> >
> > struct phy_device *mdiobus_scan(struct mii_bus *bus, int addr)
> > {
> > struct phy_device *phydev;
> > int err;
> >
> > phydev = get_phy_device(bus, addr, false);
> > if (IS_ERR(phydev) || phydev == NULL)
> > return phydev;
> >
> > So before, we return NULL, if the device was not there. Now we return
> > ERR_PTR(-ENODEV).
> >
> > This is being called by:
> >
> > int __mdiobus_register(struct mii_bus *bus, struct module *owner)
> > {
> > struct mdio_device *mdiodev;
> > ...
> > for (i = 0; i < PHY_MAX_ADDR; i++) {
> > if ((bus->phy_mask & (1 << i)) == 0) {
> > struct phy_device *phydev;
> >
> > phydev = mdiobus_scan(bus, i);
> > if (IS_ERR(phydev)) {
> > err = PTR_ERR(phydev);
> > goto error;
> > }
> > }
> > }
> >
> > This is treating ERR_PTR(-ENODEV) as a fatal error, where as before
> > IS_ERR(NULL) would be false and it would continue scanning other
> > addresses on the bus.
>
> Thank you for the detailed analysis! (And shame on me for the lack of it.)
>
> > Please revert this, or fix all the callsites such that ENODEV is not a
> > fatal error.
>
> OK, I'll do what DaveM decides.
I found one other user that remains broken: pxa168_init_phy() looks
wrong before and after the patch:
pep->phy = mdiobus_scan(pep->smi_bus, pep->phy_addr);
if (!pep->phy)
return -ENODEV;
err = phy_connect_direct(dev, pep->phy, pxa168_eth_adjust_link,
pep->phy_intf);
as phy_connect_direct() will go on and dereference an error pointer. This
should check for IS_ERR(), and with the patches applied, we can drop the
!pep->phy check.
Arnd
