[PATCH 3/3] tty: n_gsm: add TIOCMIWAIT support

D. Starke
2023-02-01T08:03:16Z

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

Add support for the TIOCMIWAIT ioctl on the virtual ttys. This enables the
user to wait for virtual modem signals like RING.

Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
---
drivers/tty/n_gsm.c | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 118511c1fa37..48fb7dad44cd 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1542,6 +1542,7 @@ static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci,
if (brk & 0x01)
tty_insert_flip_char(&dlci->port, 0, TTY_BREAK);
dlci->modem_rx = mlines;
+ wake_up_interruptible(&dlci->gsm->event);
}

/**
@@ -3848,6 +3849,35 @@ static int gsm_modem_update(struct gsm_dlci *dlci, u8 brk)
return -EPROTONOSUPPORT;
}

+/**
+ * gsm_wait_modem_change - wait for modem status line change
+ * @dlci: channel
+ * @mask: modem status line bits
+ */
+
+static int gsm_wait_modem_change(struct gsm_dlci *dlci, u32 mask)
+{
+ struct gsm_mux *gsm = dlci->gsm;
+ u32 old = dlci->modem_rx & mask;
+ int ret;
+
+ if (gsm->dead)
+ return -ENODEV;
+
+ do {
+ ret = wait_event_interruptible(gsm->event, gsm->dead
+ || old ^ (dlci->modem_rx & mask));
+ if (ret)
+ return ret;
+ if (dlci->state != DLCI_OPEN)
+ return -EL2NSYNC;
+ if (gsm->dead)
+ return -ENODEV;
+ } while ((old ^ (dlci->modem_rx & mask)) == 0);
+
+ return 0;
+}
+
static bool gsm_carrier_raised(struct tty_port *port)
{
struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
@@ -4107,6 +4137,8 @@ static int gsmtty_ioctl(struct tty_struct *tty,
gsm_destroy_network(dlci);
mutex_unlock(&dlci->mutex);
return 0;
+ case TIOCMIWAIT:
+ return gsm_wait_modem_change(dlci, arg);
default:
return -ENOIOCTLCMD;
}
--
2.34.1