Re: [PATCH v3] usb: dwc2: dwc2_vbus_supply_init: fix error check

[Tomeu Vizoso]

On 03/22/2018 02:26 PM, Heiko StÃbner wrote:
> Am Donnerstag, 22. MÃrz 2018, 14:14:51 CET schrieb Tomeu Vizoso:
> > devm_regulator_get_optional returns -ENODEV if the regulator isn't
> > there, so if that's the case we have to make sure not to leave -ENODEV
> > in the regulator pointer.
> >
> > Also, make sure we return 0 in that case, but correctly propagate any
> > other errors. Also propagate the error from _dwc2_hcd_start.
> >
> > Fixes: 531ef5ebea96 ("usb: dwc2: add support for host mode external vbus
> > supply") Cc: Amelie Delaunay <amelie.delaunay@xxxxxx>
> > Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
> >
> > ---
> >
> > v2: Only overwrite the error in the pointer after checking it (Heiko
> >      StÃbner <heiko@xxxxxxxxx>)
> > v3: Remove hunks that shouldn't be in this patch
> > ---
> >   drivers/usb/dwc2/hcd.c | 11 +++++++----
> >   1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
> > index dcfda5eb4cac..863aed20517f 100644
> > --- a/drivers/usb/dwc2/hcd.c
> > +++ b/drivers/usb/dwc2/hcd.c
> > @@ -359,8 +359,13 @@ static void dwc2_gusbcfg_init(struct dwc2_hsotg *hsotg)
> > static int dwc2_vbus_supply_init(struct dwc2_hsotg *hsotg)
> >   {
> >   	hsotg->vbus_supply = devm_regulator_get_optional(hsotg->dev, "vbus");
> > -	if (IS_ERR(hsotg->vbus_supply))
> > +	if (PTR_ERR(hsotg->vbus_supply) == -ENODEV) {
> > +		hsotg->vbus_supply = NULL;
> >   		return 0;
> > +	} else if (IS_ERR(hsotg->vbus_supply)) {
> > +		hsotg->vbus_supply = NULL;
> > +		return PTR_ERR(hsotg->vbus_supply);
> > +	}
>
> my personal cluelessnes, but can you use PTR_ERR without checking for
> IS_ERR first?

It's just a cast, so it should be fine.

> I would've expected something along the line of
>
> if (IS_ERR(hsotg->vbus_supply)) {
> 	if (PTR_ERR(hsotg->vbus_supply) == -ENODEV) {
> 		hsotg->vbus_supply = NULL;
> 		return 0;
> 	} else {
> 		return PTR_ERR(hsotg->vbus_supply);
> 	}
> }

I kind of liked to avoid one indentation level. Also wanted to play safe 
and NULLify the pointer in both code paths.

Thanks,

Tomeu