linux-kernel - Re: [PATCH v2 3/3] pwm: pwm-mediatek: Beautify error messages text

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Message-ID: <YheOk3emaxePPBdr@orome>
Date:   Thu, 24 Feb 2022 14:56:35 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Macpaul Lin <macpaul.lin@...iatek.com>
Cc:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        "lee.jones@...aro.org" <lee.jones@...aro.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "kernel@...labora.com" <kernel@...labora.com>
Subject: Re: [PATCH v2 3/3] pwm: pwm-mediatek: Beautify error messages text

On Tue, Feb 15, 2022 at 02:47:33PM +0800, Macpaul Lin wrote:
> On 2/14/22 10:03 PM, AngeloGioacchino Del Regno wrote:
> > As a cherry-on-top cleanup, make error messages clearer to read
> > by changing instances of "clock: XXXX failed" to a more readable
> > "Failed to get XXXX clock". Also add "of" to unsupported period
> > error.
> > 
> > This is purely a cosmetic change; no "real" functional changes.
> > 
> > Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> > ---
> >   drivers/pwm/pwm-mediatek.c | 8 ++++----
> >   1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c
> > index 6b39f3d69e41..568b13a48717 100644
> > --- a/drivers/pwm/pwm-mediatek.c
> > +++ b/drivers/pwm/pwm-mediatek.c
> > @@ -146,7 +146,7 @@ static int pwm_mediatek_config(struct pwm_chip *chip, struct pwm_device *pwm,
> >   	if (clkdiv > PWM_CLK_DIV_MAX) {
> >   		pwm_mediatek_clk_disable(chip, pwm);
> > -		dev_err(chip->dev, "period %d not supported\n", period_ns);
> > +		dev_err(chip->dev, "period of %d ns not supported\n", period_ns);
> >   		return -EINVAL;
> >   	}
> > @@ -229,12 +229,12 @@ static int pwm_mediatek_probe(struct platform_device *pdev)
> >   	pc->clk_top = devm_clk_get(&pdev->dev, "top");
> >   	if (IS_ERR(pc->clk_top))
> >   		return dev_err_probe(&pdev->dev, PTR_ERR(pc->clk_top),
> > -				     "clock: top failed\n");
> > +				     "Failed to get top clock\n");
> >   	pc->clk_main = devm_clk_get(&pdev->dev, "main");
> >   	if (IS_ERR(pc->clk_main))
> >   		return dev_err_probe(&pdev->dev, PTR_ERR(pc->clk_main),
> > -				     "clock: main failed\n");
> > +				     "Failed to get main clock\n");
> >   	for (i = 0; i < pc->soc->num_pwms; i++) {
> >   		char name[8];
> > @@ -244,7 +244,7 @@ static int pwm_mediatek_probe(struct platform_device *pdev)
> >   		pc->clk_pwms[i] = devm_clk_get(&pdev->dev, name);
> >   		if (IS_ERR(pc->clk_pwms[i]))
> >   			return dev_err_probe(&pdev->dev, PTR_ERR(pc->clk_pwms[i]),
> > -					     "clock: %s failed\n", name);
> > +					     "Failed to get %s clock\n", name);
> >   	}
> >   	pc->chip.dev = &pdev->dev;
> > 
> 
> The format of these debug messages "clock: top" or "clock: main" is meant to
> keep both human and machine's readability at the same time.
> This kind of format is much more easier to parse by scripts, which the
> driver's category and sub nodes are separated by delimiters . If a fail log
> has been provided, the script could indicated where the issue might exists
> probably. Device vender, field application engineer, and driver maintainer
> could be able to write and use the error log parser before debugging.

Does such a script truly exist? Given that most error messages don't
follow this format, I would expect it to be only very marginally useful.
Typically the prefix that the dev_printk() variants add is enough
information to deduct where the error happens, at which point it's back
to good old grep to find the matching string to localize exactly.

> I'm not sure if this kind of format will be better. Like, "Failed to get
> clock: %s".
> 
> If most people like this kind of solution ("Failed to get clock: %s\n"),
> then you can have the reviewed-by tag.
> Thanks!
> 
> Reviewed-by: Macpaul Lin <macpaul.lin@...iatek.com>

I'm going to assume that the scriptability is a theoretical argument, so
I'll take this. Let me know if you do rely on the exact format and I can
drop this again.

Thierry

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