linux-kernel - Re: [PATCH 1/2] soundwire: add macro to selectively change error levels

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Date:   Thu, 1 Apr 2021 22:56:45 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     Vinod Koul <vkoul@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        hui.wang@...onical.com, sanyog.r.kale@...el.com,
        rander.wang@...ux.intel.com, bard.liao@...el.com
Subject: Re: [PATCH 1/2] soundwire: add macro to selectively change error
 levels

On Thu, Apr 01, 2021 at 01:43:53PM -0500, Pierre-Louis Bossart wrote:
> 
> > > > My bigger issue with this is that this macro is crazy.  Why do you need
> > > > debugging here at all for this type of thing?  That's what ftrace is
> > > > for, do not sprinkle code with "we got this return value from here!" all
> > > > over the place like what this does.
> > > 
> > > We are not sprinkling the code all over the place with any new logs, they
> > > exist already in the SoundWire code and this patch helps filter them out.
> > > See e.g. patch 2/2
> > > 
> > > -			dev_err(&slave->dev,
> > > -				"Clk Stop type =%d failed: %d\n", type, ret);
> > > +			sdw_dev_dbg_or_err(&slave->dev, ret != -ENODATA,
> > > +					   "Clk Stop mode %d type =%d failed: %d\n",
> > > +					   mode, type, ret);
> > 
> > You just added a debug log for no reason.
> 
> The number of logs is lower when dynamic debug is not enabled, and equal
> when it is. there's no addition.
> 
> The previous behavior was unconditional dev_err that everyone sees.
> 
> Now it's dev_err ONLY when the code is NOT -ENODATA, and dev_dgb otherwise,
> meaning it will seen ONLY be seen IF dynamic debug is enabled for
> drivers/soundwire/bus.c
> 
> Allow me to use another example from patch2:
> 
> -		if (ret == -ENODATA)
> -			dev_dbg(bus->dev,
> -				"ClockStopNow Broadcast msg ignored %d", ret);
> -		else
> -			dev_err(bus->dev,
> -				"ClockStopNow Broadcast msg failed %d", ret);
> +		sdw_dev_dbg_or_err(bus->dev, ret != -ENODATA,
> +				   "ClockStopNow Broadcast msg failed %d\n", ret);
> 
> There's no new log, is there?

No, but that is not what you showed above which was just an error
message being replaced with both a debug and an error message.

Just drop the debug messages, they are pointless, right?

thanks,

greg k-h