tty: n_gsm: Save dlci address open status when config requester

When n_gsm config "initiator=0",as requester ,receive SABM frame,n_gsm
register gsmtty dev,and save dlci open address status,if receive DLC0
DISC or CLD frame,it can unregister the gsmtty dev by saving dlci address.

Signed-off-by: Zhenguo Zhao <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/n_gsm.c

···
 
 static struct tty_driver *gsm_tty_driver;
 
+/* Save dlci open address */
+static int addr_open[256] = { 0 };
+/* Save dlci open count */
+static int addr_cnt;
 /*
  *	This section of the driver logic implements the GSM encodings
  *	both the basic and the 'advanced'. Reliable transport is not
···
 }
 
 static void gsm_dlci_begin_close(struct gsm_dlci *dlci);
+static void gsm_dlci_close(struct gsm_dlci *dlci);
 
 /**
  *	gsm_control_message	-	DLCI 0 control processing
···
 {
 	u8 buf[1];
 	unsigned long flags;
+	struct gsm_dlci *dlci;
+	int i;
+	int address;
 
 	switch (command) {
 	case CMD_CLD: {
-		struct gsm_dlci *dlci = gsm->dlci[0];
+		if (addr_cnt > 0) {
+			for (i = 0; i < addr_cnt; i++) {
+				address = addr_open[i];
+				dlci = gsm->dlci[address];
+				gsm_dlci_close(dlci);
+				addr_open[i] = 0;
+			}
+		}
 		/* Modem wishes to close down */
+		dlci = gsm->dlci[0];
 		if (dlci) {
 			dlci->dead = true;
 			gsm->dead = true;
-			gsm_dlci_begin_close(dlci);
+			gsm_dlci_close(dlci);
+			addr_cnt = 0;
+			gsm_response(gsm, 0, UA|PF);
 		}
 		}
 		break;
···
 	struct gsm_dlci *dlci;
 	u8 cr;
 	int address;
+	int i, j, k, address_tmp;
 	/* We have to sneak a look at the packet body to do the FCS.
 	   A somewhat layering violation in the spec */
 
···
 		else {
 			gsm_response(gsm, address, UA|PF);
 			gsm_dlci_open(dlci);
+			/* Save dlci open address */
+			if (address) {
+				addr_open[addr_cnt] = address;
+				addr_cnt++;
+			}
 		}
 		break;
 	case DISC|PF:
···
 			return;
 		}
 		/* Real close complete */
-		gsm_response(gsm, address, UA|PF);
-		gsm_dlci_close(dlci);
+		if (!address) {
+			if (addr_cnt > 0) {
+				for (i = 0; i < addr_cnt; i++) {
+					address = addr_open[i];
+					dlci = gsm->dlci[address];
+					gsm_dlci_close(dlci);
+					addr_open[i] = 0;
+				}
+			}
+			dlci = gsm->dlci[0];
+			gsm_dlci_close(dlci);
+			addr_cnt = 0;
+			gsm_response(gsm, 0, UA|PF);
+		} else {
+			gsm_response(gsm, address, UA|PF);
+			gsm_dlci_close(dlci);
+			/* clear dlci address */
+			for (j = 0; j < addr_cnt; j++) {
+				address_tmp = addr_open[j];
+				if (address_tmp == address) {
+					for (k = j; k < addr_cnt; k++)
+						addr_open[k] = addr_open[k+1];
+				addr_cnt--;
+				break;
+				}
+			}
+		}
 		break;
 	case UA:
 	case UA|PF: