linux-kernel - Re: [PATCH v3 2/3] drm/bridge: parade-ps8640: Use regmap APIs

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Date:   Tue, 14 Sep 2021 19:17:03 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Philip Chen <philipchen@...omium.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v3 2/3] drm/bridge: parade-ps8640: Use regmap APIs

Hi,

On Tue, Sep 14, 2021 at 5:29 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Philip Chen (2021-09-14 16:28:44)
> > diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> > index e340af381e05..8d3e7a147170 100644
> > --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> > +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> > @@ -368,6 +396,12 @@ static int ps8640_probe(struct i2c_client *client)
> >
> >         ps_bridge->page[PAGE0_DP_CNTL] = client;
> >
> > +       ps_bridge->regmap[PAGE0_DP_CNTL] = devm_regmap_init_i2c(client, ps8640_regmap_config);
> > +       if (IS_ERR(ps_bridge->regmap[PAGE0_DP_CNTL])) {
> > +               return dev_err_probe(dev, PTR_ERR(ps_bridge->regmap[PAGE0_DP_CNTL]),
> > +                                    "Error initting page 0 regmap\n");
>
> This one also doesn't return -EPROBE_DEFER? The dev_err_probe() should
> really only be used on "get" style APIs that can defer.

Any reason why you say that dev_err_probe() should only be used on
"get" style APIs that can defer? Even if an API can't return
-EPROBE_DEFER, using dev_err_probe() still (IMO) makes the code
cleaner and should be used for any error cases like this during probe.
Why?

* It shows the error code in a standard way for you.
* It returns the error code you passed it so you can make your error
return "one line" instead of 2.

Is there some bad thing about dev_err_probe() that makes it
problematic to use? If not then the above advantages should be a net
win, right?

-Doug