linux-kernel - [PATCH v3 6/6] tty: n_gsm: add debug bit for user payload

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Message-Id: <20220831073800.7459-6-daniel.starke@siemens.com>
Date:   Wed, 31 Aug 2022 09:38:00 +0200
From:   "D. Starke" <daniel.starke@...mens.com>
To:     linux-serial@...r.kernel.org, gregkh@...uxfoundation.org,
        jirislaby@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        Daniel Starke <daniel.starke@...mens.com>
Subject: [PATCH v3 6/6] tty: n_gsm: add debug bit for user payload

From: Daniel Starke <daniel.starke@...mens.com>

A debug bit to output a complete transmission dump exists. Sometimes only
the user frames are relevant. Add an additional bit which limits the
transmission dump output to user data frames if set.

Signed-off-by: Daniel Starke <daniel.starke@...mens.com>
---
 drivers/tty/n_gsm.c | 5 +++++
 1 file changed, 5 insertions(+)

Incorporated review comments from Jiri Slaby since v2:
- changed (1 << n) to BIT(n) in the debug macro definitions

Link: https://lore.kernel.org/all/1d8d0d72-a5b7-724e-a70a-71d9fd3330c4@kernel.org/

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index f8a8c4059907..6588b84eed96 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -69,6 +69,7 @@ module_param(debug, int, 0600);
 #define DBG_DATA	BIT(2) /* Data transmission details. */
 #define DBG_ERRORS	BIT(3) /* Details for fail conditions. */
 #define DBG_TTY		BIT(4) /* Transmission statistics for DLCI TTYs. */
+#define DBG_PAYLOAD	BIT(5) /* Limits DBG_DUMP to payload frames. */
 
 /* Defaults: these are from the specification */
 
@@ -598,6 +599,10 @@ static void gsm_print_packet(const char *hdr, int addr, int cr,
 {
 	if (!(debug & DBG_DUMP))
 		return;
+	/* Only show user payload frames if debug & DBG_PAYLOAD */
+	if (!(debug & DBG_PAYLOAD) && addr != 0)
+		if ((control & ~PF) == UI || (control & ~PF) == UIH)
+			return;
 
 	pr_info("%s %d) %c: ", hdr, addr, "RC"[cr]);
 
-- 
2.34.1