linux-kernel - [PATCH 15/20] tty: n_gsm: fix missing update of modem controls after DLCI open

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Date:   Thu, 14 Apr 2022 02:42:20 -0700
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 15/20] tty: n_gsm: fix missing update of modem controls after DLCI open

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

Currently the peer is not informed about the initial state of the modem
control lines after a new DLCI has been opened.
Fix this by sending the initial modem control line states after DLCI open.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline")
Cc: stable@...r.kernel.org
Signed-off-by: Daniel Starke <daniel.starke@...mens.com>
---
 drivers/tty/n_gsm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index f3fb66be8513..e9a7d9483c1f 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -369,7 +369,11 @@ static const u8 gsm_fcs8[256] = {
 #define INIT_FCS	0xFF
 #define GOOD_FCS	0xCF
 
+/*
+ * Prototypes
+ */
 static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len);
+static int gsmtty_modem_update(struct gsm_dlci *dlci, u8 brk);
 
 /**
  *	gsm_fcs_add	-	update FCS
@@ -1479,6 +1483,8 @@ static void gsm_dlci_open(struct gsm_dlci *dlci)
 		pr_debug("DLCI %d goes open.\n", dlci->addr);
 	/* Register gsmtty driver,report gsmtty dev add uevent for user */
 	tty_register_device(gsm_tty_driver, dlci->addr, NULL);
+	if (dlci->addr) /* Send current modem state */
+		gsmtty_modem_update(dlci, 0);
 	wake_up(&dlci->gsm->event);
 }
 
-- 
2.25.1