FAILED: patch "[PATCH] tty: n_gsm: fix missing update of modem controls after DLCI" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 48473802506d2d6151f59e0e764932b33b53cb3b Mon Sep 17 00:00:00 2001
From: Daniel Starke <[email protected]>
Date: Wed, 20 Apr 2022 03:13:44 -0700
Subject: [PATCH] tty: n_gsm: fix missing update of modem controls after DLCI
open

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.

index e440c7f6d20e..979dc9151383 100644
@@ -370,6 +370,7 @@ static const u8 gsm_fcs8[256] = {
 #define GOOD_FCS	0xCF
 
 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

@@ -1483,6 +1484,9 @@ 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);
+	/* Send current modem state */
+	if (dlci->addr)
+		gsmtty_modem_update(dlci, 0);
 	wake_up(&dlci->gsm->event);
 }