linux-kernel - Re: [PATCH 03/10] mfd / platform: cros_ec: Miscellaneous character device to talk with the EC

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Message-ID: <beaf3554bb85974eb118d7722ca55f1823b1850c.camel@collabora.com>
Date:   Tue, 04 Jun 2019 13:58:38 -0300
From:   Ezequiel Garcia <ezequiel@...labora.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     linux-kernel@...r.kernel.org, gwendal@...omium.org,
        Guenter Roeck <groeck@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Lee Jones <lee.jones@...aro.org>, kernel@...labora.com,
        dtor@...omium.org,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        linux-doc@...r.kernel.org, Enno Luebbers <enno.luebbers@...el.com>,
        Guido Kiener <guido@...ner-muenchen.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kishon Vijay Abraham I <kishon@...com>,
        Jonathan Corbet <corbet@....net>, Wu Hao <hao.wu@...el.com>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Tycho Andersen <tycho@...ho.ws>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Jilayne Lovejoy <opensource@...ayne.com>
Subject: Re: [PATCH 03/10] mfd / platform: cros_ec: Miscellaneous character
 device to talk with the EC

Hey Greg,

> > +	dev_info(&pdev->dev, "Created misc device /dev/%s\n",
> > +		 data->misc.name);
> 
> No need to be noisy, if all goes well, your code should be quiet.
> 

I sometimes wonder about this being noise or not, so I will slightly
hijack this thread for this discussion.

>From a kernel developer point-of-view, or even from a platform
developer or user with a debugging hat point-of-view, having
a "device created" or "device registered" message is often very useful.

In fact, I wish people would do this more often, so I don't have to
deal with dynamic debug, or hack my way:

diff --git a/drivers/media/i2c/ov5647.c b/drivers/media/i2c/ov5647.c
index 4589631798c9..473549b26bb2 100644
--- a/drivers/media/i2c/ov5647.c
+++ b/drivers/media/i2c/ov5647.c
@@ -603,7 +603,7 @@ static int ov5647_probe(struct i2c_client *client,
        if (ret < 0)
                goto error;
 
-       dev_dbg(dev, "OmniVision OV5647 camera driver probed\n");
+       dev_info(dev, "OmniVision OV5647 camera driver probed\n");
        return 0;
 error:
        media_entity_cleanup(&sd->entity);

In some subsystems, it's even a behavior I'm more or less relying on:

$ git grep v4l2_info.*registered drivers/media/ | wc -l
26

And on the downsides, I can't find much. It's just one little line,
that is not even noticed unless you have logging turned on.

Thanks,
Ezequiel