linux-kernel - Re: [PATCH 1/3] tty: n_gsm: Improve debug output

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Message-ID: <344a3762-ddbe-f57a-6929-83bf255736ca@suse.cz>
Date:   Mon, 4 May 2020 08:37:36 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     Gregory CLEMENT <gregory.clement@...tlin.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 1/3] tty: n_gsm: Improve debug output

On 30. 04. 20, 13:34, Gregory CLEMENT wrote:
> Use appropriate print helpers for debug messages.
> 
> Signed-off-by: Gregory CLEMENT <gregory.clement@...tlin.com>
> ---
>  drivers/tty/n_gsm.c | 18 +++++-------------
>  1 file changed, 5 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
> index d77ed82a4840..4965e39e0223 100644
> --- a/drivers/tty/n_gsm.c
> +++ b/drivers/tty/n_gsm.c
> @@ -459,7 +459,7 @@ static void gsm_print_packet(const char *hdr, int addr, int cr,
>  	if (!(debug & 1))
>  		return;
>  
> -	pr_info("%s %d) %c: ", hdr, addr, "RC"[cr]);
> +	pr_debug("%s %d) %c: ", hdr, addr, "RC"[cr]);

Now, you need both debug=1 module parameter *and* fiddling with
dynamic_debug, if enabled. And it is enabled in most distros…

We don't have any unconditional KERN_DEBUG printk helper, unfortunately.

>  	switch (control & ~PF) {
>  	case SABM:
> @@ -504,18 +504,10 @@ static void gsm_print_packet(const char *hdr, int addr, int cr,
>  	else
>  		pr_cont("(F)");
>  
> -	if (dlen) {
> -		int ct = 0;
> -		while (dlen--) {
> -			if (ct % 8 == 0) {
> -				pr_cont("\n");
> -				pr_debug("    ");
> -			}
> -			pr_cont("%02X ", *data++);
> -			ct++;
> -		}
> -	}
> -	pr_cont("\n");
> +	if (dlen)

print_hex_dump* handle zero len quite well. No need for the if.

> +		print_hex_dump_bytes("", DUMP_PREFIX_NONE, data, dlen);
> +
> +	pr_debug("\n");

This is superfluous too. It was intended as the last \n in the previous
code.

thanks,
-- 
js
suse labs