[PATCH] drm: rcar-du: Use dev_err_probe() helper

[Laurent Pinchart]

Hi Geert,

On Wed, Dec 08, 2021 at 07:23:25PM +0100, Geert Uytterhoeven wrote:
> On Wed, Dec 8, 2021 at 7:00 PM Laurent Pinchart wrote:
> > On Wed, Dec 08, 2021 at 11:57:21AM +0000, Kieran Bingham wrote:
> > > Quoting Geert Uytterhoeven (2021-12-08 10:30:53)
> > > > Use the dev_err_probe() helper, instead of open-coding the same
> > > > operation.
> > > >
> > > > Signed-off-by: Geert Uytterhoeven <geert+renesas at glider.be>
> > > > ---
> > > >  drivers/gpu/drm/rcar-du/rcar_du_drv.c | 5 ++---
> > > >  1 file changed, 2 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_drv.c b/drivers/gpu/drm/rcar-du/rcar_du_drv.c
> > > > index 5612a9e7a9056cf7..86eeda769e2ebd10 100644
> > > > --- a/drivers/gpu/drm/rcar-du/rcar_du_drv.c
> > > > +++ b/drivers/gpu/drm/rcar-du/rcar_du_drv.c
> > > > @@ -661,9 +661,8 @@ static int rcar_du_probe(struct platform_device *pdev)
> > > >         /* DRM/KMS objects */
> > > >         ret = rcar_du_modeset_init(rcdu);
> > > >         if (ret < 0) {
> > > > -               if (ret != -EPROBE_DEFER)
> > > > -                       dev_err(&pdev->dev,
> > > > -                               "failed to initialize DRM/KMS (%d)\n", ret);
> > > > +               dev_err_probe(&pdev->dev, ret,
> > > > +                             "failed to initialize DRM/KMS\n");
> > >
> > > I've just learned that dev_err_probe() sets a 'reason' for the deferral.
> > > Seems like a nice feature when exploring devices that are still waiting
> > > to probe. Is the message still appropriate enough in that case?
> >
> > It's a very generic message, so it's not ideal. One issue is that
> > dev_err_probe() replaces any currently stored probe deferral reason
> > message, which means that we'll override any message previously set. We
> > don't set any message now, but we should (in rcar_du_encoder_init(),
> > there are two main code paths where -EPROBE_DEFER is expected), so this
> > patch would then get in the way I'm afraid.
> 
> If rcar_du_encoder_init() will handle the printing of errors, there is indeed
> no more reason for rcar_du_probe() to do that, so the existing dev_err()
> with the fuzzy message can be removed?

We could drop the above message indeed, at least once all the error
paths deeper in the call stack will print a detailed message. The
message here is useful in case an error path forgets to print anything,
to avoid the worst case of probe() failing silently.

-- 
Regards,

Laurent Pinchart