linux-kernel - Re: [PATCH 2/2] vfio: platform: Add generic DT reset support

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Date:   Thu, 22 Feb 2018 10:36:04 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Baptiste Reynal <b.reynal@...tualopensystems.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        KVM list <kvm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] vfio: platform: Add generic DT reset support

Hi Geert,

On Thu, 2018-02-22 at 09:50 +0100, Geert Uytterhoeven wrote:
[...]
> > > @@ -127,8 +134,15 @@ static int vfio_platform_get_reset(struct vfio_platform_device *vdev)
> > >               vdev->of_reset = vfio_platform_lookup_reset(vdev->compat,
> > >                                                       &vdev->reset_module);
> > >       }
> > > +     if (vdev->of_reset)
> > > +             return 0;
> > > +
> > > +     vdev->reset_control = __of_reset_control_get(vdev->device->of_node,
> > > +                                                  NULL, 0, false, false);
> > > +     if (!IS_ERR(vdev->reset_control))
> > > +             return 0;
> > 
> > if you assign to a local variable first here:
> > 
> >         struct reset_control *rstc;
> > 
> >          ...
> > 
> >         rstc = of_reset_control_get_exclusive(vdev->device->of_node, NULL);
> >         if (!IS_ERR(rstc)) {
> >                 vdev->reset_control = rstc;
> >                 return 0;
> >         }
> > 
> > Also, please don't use __of_reset_control_get directly.
> 
> OK, apparently I didn't read <linux/reset.h> beyond the first #else...

I don't blame you, this is missing some documentation.

> > > @@ -217,6 +233,9 @@ static int vfio_platform_call_reset(struct vfio_platform_device *vdev,
> > >       } else if (vdev->of_reset) {
> > >               dev_info(vdev->device, "reset\n");
> > >               return vdev->of_reset(vdev);
> > > +     } else if (!IS_ERR_OR_NULL(vdev->reset_control)) {
> > > +             dev_info(vdev->device, "reset\n");
> > > +             return reset_control_reset(vdev->reset_control);
> > 
> >         } else {
> >                 if (vdev->reset_control)
> >                         dev_info(vdev->device, "reset\n");
> >                 return reset_control_reset(vdev->reset_control);
> > 
> > >       }
> 
> I'd like to keep the "else if", as that's the pattern used by the blocks above.

my bad, there's more code after this.

	} else if (vdev->reset_control) {
		dev_info(vdev->device, "reset\n");
		return reset_control_reset(vdev->reset_control);
	}

is better as it doesn't lose the warning if vdev->reset_control == NULL.
It seems I've focused too much on getting rid of the IS_ERR_OR_NULL
macro.

regards
Philipp