Re: [PATCH 2/2] usb: core: phy: fix return value checking about devm_of_phy_get_by_index()

[Chunfeng Yun <chunfeng.yun@mediatek.com>]

On Sun, 2018-06-24 at 20:00 +0200, Martin Blumenstingl wrote:
> Hello Chunfeng,
> 
> thank you for the patch!
> 
> On Fri, Jun 22, 2018 at 8:33 AM Chunfeng Yun <chunfeng.yun@mediatek.com> wrote:
> >
> > 1. use IS_ERR() but not IS_ERR_OR_NULL() because devm_of_phy_get_by_index()
> >     never return NULL value;
> ACK - good catch!
> 
> > 2. devm_of_phy_get_by_index() should not fail for a valid index
> I have learned that the PHY framework can return -ENODEV if the PHY is:
> 1. supposed to be handled by the legacy USB PHY framework
> 2. the PHY node is disabled in devicetree
A little confused, we can avoid this error by not using a disabled or
"usb-nop-xceiv" phy in host node.

If ignore error of -ENODEV, we will also skip an error case which we
don't want it happen. 

> 
> see [0] for the code in the PHY framework and [1] for the discussion
> with Johan (who informed me of case #1, I added him on this mail)
> 
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
> > ---
> >  drivers/usb/core/phy.c | 11 ++++-------
> >  1 file changed, 4 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/usb/core/phy.c b/drivers/usb/core/phy.c
> > index 9879767..0f972e1 100644
> > --- a/drivers/usb/core/phy.c
> > +++ b/drivers/usb/core/phy.c
> > @@ -23,14 +23,11 @@ static int usb_phy_roothub_add_phy(struct device *dev, int index,
> >                                    struct list_head *list)
> >  {
> >         struct usb_phy_roothub *roothub_entry;
> > -       struct phy *phy = devm_of_phy_get_by_index(dev, dev->of_node, index);
> > +       struct phy *phy;
> >
> > -       if (IS_ERR_OR_NULL(phy)) {
> > -               if (!phy || PTR_ERR(phy) == -ENODEV)
> > -                       return 0;
> > -               else
> > -                       return PTR_ERR(phy);
> > -       }
> > +       phy = devm_of_phy_get_by_index(dev, dev->of_node, index);
> > +       if (IS_ERR(phy))
> > +               return PTR_ERR(phy);
> @Johan can you please review this as well? maybe we need to keep the
> -ENODEV check
> 
> 
> Regards
> Martin
> 
> 
> [0] https://elixir.bootlin.com/linux/v4.18-rc2/source/drivers/phy/phy-core.c#L421
> [1] https://lkml.org/lkml/2018/4/19/88