linux-kernel - Re: [RESEND PATCH v5 5/5] drm/bridge: lvds-codec: simplify error handling code

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Message-ID: <20200624211849.GB29023@pendragon.ideasonboard.com>
Date:   Thu, 25 Jun 2020 00:18:49 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Andrzej Hajda <a.hajda@...sung.com>
Cc:     Jernej Skrabec <jernej.skrabec@...l.net>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-kernel@...r.kernel.org,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>, andy.shevchenko@...il.com,
        Mark Brown <broonie@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [RESEND PATCH v5 5/5] drm/bridge: lvds-codec: simplify error
 handling code

Hi Andrzej,

On Wed, Jun 24, 2020 at 04:03:30PM +0200, Andrzej Hajda wrote:
> On 24.06.2020 15:33, Laurent Pinchart wrote:
> > On Wed, Jun 24, 2020 at 01:41:27PM +0200, Andrzej Hajda wrote:
> >> Using probe_err code has following advantages:
> >> - shorter code,
> >> - recorded defer probe reason for debugging,
> >> - uniform error code logging.
> >>
> >> Signed-off-by: Andrzej Hajda <a.hajda@...sung.com>
> >> ---
> >>   drivers/gpu/drm/bridge/lvds-codec.c | 9 ++-------
> >>   1 file changed, 2 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/bridge/lvds-codec.c b/drivers/gpu/drm/bridge/lvds-codec.c
> >> index 24fb1befdfa2..c76fa0239e39 100644
> >> --- a/drivers/gpu/drm/bridge/lvds-codec.c
> >> +++ b/drivers/gpu/drm/bridge/lvds-codec.c
> >> @@ -71,13 +71,8 @@ static int lvds_codec_probe(struct platform_device *pdev)
> >>   	lvds_codec->connector_type = (uintptr_t)of_device_get_match_data(dev);
> >>   	lvds_codec->powerdown_gpio = devm_gpiod_get_optional(dev, "powerdown",
> >>   							     GPIOD_OUT_HIGH);
> >> -	if (IS_ERR(lvds_codec->powerdown_gpio)) {
> >> -		int err = PTR_ERR(lvds_codec->powerdown_gpio);
> >> -
> >> -		if (err != -EPROBE_DEFER)
> >> -			dev_err(dev, "powerdown GPIO failure: %d\n", err);
> >> -		return err;
> >> -	}
> >> +	if (IS_ERR(lvds_codec->powerdown_gpio))
> >> +		return probe_err(dev, lvds_codec->powerdown_gpio, "powerdown GPIO failure\n");
> >
> > Line wrap please.
> 
> I hoped that with latest checkpatch line length limit increase from 80 
> to 100 it is acceptable :) but apparently not [1].

I'm all for using longer lines when that improves readability, but in
this case I think it's easy enough to split the line. A longer line
limit doesn't mean we're forced to generate longer lines :-)

On a side note, I've been working on a C++ userspace project where we
had to decide on a coding style. Line length was one parameter, and we
went for a soft limit of 80 columns, and a hard limit of 120 columns.
This works quite well so far. The only pain point is that clang-format
(we use it, wrapped in a python script, to detect coding style
violations) doesn't understand soft and hard limits for line lengths.

> [1]: 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bdc48fa11e46f867ea4d75fa59ee87a7f48be144
>
> > It bothers me that the common pattern of writing the error code at the
> > end of the message isn't possible anymore. Maybe I'll get used to it,
> > but it removes some flexibility.
> 
> Yes, but it gives uniformity :) and now with %pe printk format it 
> changes anyway.
> 
> >>   	/* Locate the panel DT node. */
> >>   	panel_node = of_graph_get_remote_node(dev->of_node, 1, 0);

-- 
Regards,

Laurent Pinchart