linux-kernel - Re: [PATCH v2 3/3] tty: n_gsm: add parameter negotiation support

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Message-ID: <DB9PR10MB5881479C5BE3D2A97A7D354CE0379@DB9PR10MB5881.EURPRD10.PROD.OUTLOOK.COM>
Date:   Mon, 31 Oct 2022 13:26:50 +0000
From:   "Starke, Daniel" <daniel.starke@...mens.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "jirislaby@...nel.org" <jirislaby@...nel.org>,
        "ilpo.jarvinen@...ux.intel.com" <ilpo.jarvinen@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] tty: n_gsm: add parameter negotiation support

Thank you for your review.

> > +		pr_err("%s: unsupported frame type %d\n", __func__,
> > +		       dlci->ftype);
>
> This needs to be dev_err(), right?

There is no place within this driver that uses dev_*() at the moment except
for the timeout function of the network stack (gsm_mux_net_tx_timeout()).
I do not mind either way, but I would prefer a consistent variant within
this driver. Therefore, I suggest switching from pr_*() to dev_*() in a
separate patch.

> And why is it not just dev_dbg()/

I used pr_err() instead of pr_dbg() due to the fact that this mismatch will
most likely make it impossible to use the n_gsm driver with the connected
device as it stands. I am okay to replace it with pr_info() though.

> > +		pr_err("%s: unsupported adaption %d\n", __func__,
> > +		       dlci->adaption);
>
> Again, dev_dbg()?
>
> Do not yet userspace, or external devices, spam kernel logs with
> messages.

These are related to the user API. Therefore, I do not mind changing these
to debug level.

> > +	if (n1 < MIN_MTU) {
> > +		if (debug & DBG_ERRORS)
>
> Please use the proper debug code in the kernel, don't roll your own.

Again, I am only reusing what is already there in the driver. To avoid
segmentation I suggest cleaning this up in a future patch.

> > +			pr_info("%s N1 out of range in PN\n", __func__);
>
> This should be dev_dbg().

Same as above. The connected device appears to be incompatible with the
based standard. It will most likely not work. Should it be debug level,
nevertheless?

> And never use __func__ in a dev_dbg() call, it's there automatically.

I could not find a hint that __func__ is included in dev_dbg(). What is
included is the subsystem name and the device name but not the function
name within the driver according to include/linux/dev_printk.h. Other
device drivers like usb/dwc2/core.c also include __func__ here. But it
appears to be possible to automate this by re-defining dev_fmt().

Please let me know if you prefer me to segment the current printk-related
code by introducing dev_*() or keep this change open for a later patch.

Best regards,
Daniel Starke