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Commit c99a841d authored by Pratham Pratap's avatar Pratham Pratap Committed by Gerrit - the friendly Code Review server
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usb: gadget: cdev: Add spinlock to synchronize ports->cbits_updated 



Consider a scenario in which open, write and close of AT port is being
done repeatedly. At some point in time, cbits_updated in f_cdev
structure gets overwritten by the previous close instance causing the AT
port to go unresponsive. This prevents port bridge service from sending
DTR/RTS settings to at_mdm0 from at_usb0.

Fix this by adding spinlock to synchronise the updation of
ports->cbits_updated field in f_cdev structure.

Change-Id: Ibf39aa90f3918cd5f22e32a3b06685db4c4298ae
Signed-off-by: default avatarPratham Pratap <quic_ppratap@quicinc.com>
parent 0c5f471d

drivers/usb/gadget/function/f_cdev.c

+6 −0
Original line number Diff line number Diff line
@@ -1617,6 +1617,7 @@ static long f_cdev_ioctl(struct file *fp, unsigned int cmd, 
	int i = 0;

	uint32_t val;

	struct f_cdev *port;

	unsigned long flags;



	port = fp->private_data;

	if (!port) {
@@ -1638,11 +1639,13 @@ static long f_cdev_ioctl(struct file *fp, unsigned int cmd, 
		break;

	case TIOCMGET:

		pr_debug("TIOCMGET on port(%s)%pK\n", port->name, port);

		spin_lock_irqsave(&port->port_lock, flags);

		ret = f_cdev_tiocmget(port);

		if (ret >= 0) {

			ret = put_user(ret, (uint32_t *)arg);

			port->cbits_updated = false;

		}

		spin_unlock_irqrestore(&port->port_lock, flags);

		break;

	default:

		pr_err("Received cmd:%d not supported\n", cmd);
@@ -1658,6 +1661,7 @@ static void usb_cser_notify_modem(void *fport, int ctrl_bits) 
	int temp;

	struct f_cdev *port = fport;

	struct cserial *cser;

	unsigned long flags;



	cser = &port->port_usb;

	if (!port) {
@@ -1672,6 +1676,7 @@ static void usb_cser_notify_modem(void *fport, int ctrl_bits) 
	if (temp == port->cbits_to_modem)

		return;



	spin_lock_irqsave(&port->port_lock, flags);

	port->cbits_to_modem = temp;

	port->cbits_updated = true;
@@ -1686,6 +1691,7 @@ static void usb_cser_notify_modem(void *fport, int ctrl_bits) 
			cser->send_modem_ctrl_bits(cser, cbits_to_laptop);

	}



	spin_unlock_irqrestore(&port->port_lock, flags);

	wake_up(&port->read_wq);

}