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SubjectRe: [PATCH 03/10] mfd / platform: cros_ec: Miscellaneous character device to talk with the EC
On Tue, Jun 04, 2019 at 11:39:21AM -0700, Guenter Roeck wrote:
> On Tue, Jun 4, 2019 at 11:35 AM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Tue, Jun 04, 2019 at 01:58:38PM -0300, Ezequiel Garcia wrote:
> > > 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.
> >
> > For you, yes. For someone with 30000 devices attached to their system,
> > it is not, and causes booting to take longer than it should be.
> >
> > > 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.
> >
> > Its better to be quiet, which is why the "default driver registration"
> > macros do not have any printk messages in them. When converting drivers
> > over to it, we made the boot process much more sane, don't try to go and
> > add messages for no good reason back in please.
> >
> > dynamic debugging can be enabled on a module and line-by-line basis,
> > even from the boot command line. So if you need debugging, you can
> > always ask someone to just reboot or unload/load the module and get the
> > message that way.
> >
>
> Can we by any chance make this an official policy ? I am kind of tired
> having to argue about this over and over again.

Sure, but how does anyone make any "official policy" in the kernel? :)

I could just go through and delete all "look ma, a new driver/device!"
messages, but that might be annoying...

thanks,

greg k-h

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